1. Cell Structure and Organisation - Syllacon Notes



Syllacon NOTESSINGAPORE-CAMBRIDGE GCE O-LEVELBIOLOGY OUTLINESYLLABUS 5158UPDATED 20 JAN 2014OverviewThemesChaptersCountI. Principles of Biology1-33II. Maintenance and Regulation of Life Processes4-118III. Continuity of Life12-154IV. Man and his Environment161 TOC \o "1-1" \h \z \u 1. Cell Structure and Organisation PAGEREF _Toc378009445 \h 102. Movement of Substances PAGEREF _Toc378009446 \h 153. Biological Molecules PAGEREF _Toc378009447 \h 184. Nutrition in Humans PAGEREF _Toc378009448 \h 245. Nutrition in Plants PAGEREF _Toc378009449 \h 306. Transport in Flowering Plants PAGEREF _Toc378009450 \h 357. Transport in Humans PAGEREF _Toc378009451 \h 398. Respiration in Humans PAGEREF _Toc378009452 \h 459. Excretion in Humans PAGEREF _Toc378009453 \h 5010. Homeostasis PAGEREF _Toc378009454 \h 5311. Co-ordination and Response PAGEREF _Toc378009455 \h 5512. Reproduction PAGEREF _Toc378009456 \h 6113. Cell Division PAGEREF _Toc378009457 \h 7014. Molecular Genetics PAGEREF _Toc378009458 \h 7315. Inheritance PAGEREF _Toc378009459 \h 7616. Organisms and their Environment PAGEREF _Toc378009460 \h 83 Note to student:Spot an error? Think that you can improve the outline?Download the .docx format of this document from the website and edit the outline yourself!Alternatively, you may wish to email the site owner at lim.ting.jie.2012@vjc.sg with the subject title: ‘Outline Feedback: O Level Biology Outline’Contents TOC \o "1-3" \h \z \u 1. Cell Structure and Organisation PAGEREF _Toc378015535 \h 10(a) identify cell structures (including organelles) of typical plant and animal cells from diagrams, photomicrographs and as seen under the light microscope using prepared slides and fresh material treated with an appropriate temporary staining technique: ? chloroplasts ? cell membrane ? cell wall ? cytoplasm ? cell vacuoles (large, sap-filled in plant cells, small, temporary in animal cells) ? nucleus PAGEREF _Toc378015536 \h 10(b) identify the following membrane systems and organelles from diagrams and electron micrographs: ? endoplasmic reticulum ? mitochondria ? Golgi body ? ribosomes PAGEREF _Toc378015537 \h 11(c) state the functions of the membrane systems and organelles identified above PAGEREF _Toc378015538 \h 12(d) compare the structure of typical animal and plant cells PAGEREF _Toc378015539 \h 12(e) state, in simple terms, the relationship between cell function and cell structure for the following: ? absorption – root hair cells ? conduction and support – xylem vessels ? transport of oxygen – red blood cells PAGEREF _Toc378015540 \h 13(f) differentiate cell, tissue, organ and organ system PAGEREF _Toc378015541 \h 142. Movement of Substances PAGEREF _Toc378015542 \h 15(a) define diffusion and discuss its importance in nutrient uptake and gaseous exchange in plants and humans PAGEREF _Toc378015543 \h 15(b) define osmosis and discuss the effects of osmosis on plant and animal tissues PAGEREF _Toc378015544 \h 16(c) define active transport and discuss its importance as an energy-consuming process by which substances are transported against a concentration gradient, as in ion uptake by root hairs and uptake of glucose by cells in the villi PAGEREF _Toc378015545 \h 173. Biological Molecules PAGEREF _Toc378015546 \h 18(a) state the roles of water in living organisms PAGEREF _Toc378015547 \h 18(b) list the chemical elements which make up: ? carbohydrates ? fats ? proteins PAGEREF _Toc378015548 \h 18(c) describe and carry out tests for: ? starch (iodine in potassium iodide solution) ? reducing sugars (Benedict’s solution) ? protein (biuret test) ? fats (ethanol emulsion) PAGEREF _Toc378015549 \h 19(d) state that large molecules are synthesised from smaller basic units: ? glycogen from glucose ? polypeptides and proteins from amino acids ? lipids such as fats from glycerol and fatty acids PAGEREF _Toc378015550 \h 20(e) explain enzyme action in terms of the ‘lock and key’ hypothesis PAGEREF _Toc378015551 \h 20(f) explain the mode of action of enzymes in terms of an active site, enzyme-substrate complex, lowering of activation energy and enzyme specificity PAGEREF _Toc378015552 \h 21(g) investigate and explain the effects of temperature and pH on the rate of enzyme catalysed reactions PAGEREF _Toc378015553 \h 224. Nutrition in Humans PAGEREF _Toc378015554 \h 24(a) describe the functions of main regions of the alimentary canal and the associated organs: mouth, salivary glands, oesophagus, stomach, duodenum, pancreas, gall bladder, liver, ileum, colon, rectum, anus, in relation to ingestion, digestion, absorption, assimilation and egestion of food, as appropriate PAGEREF _Toc378015555 \h 24(b) describe peristalsis in terms of rhythmic wave-like contractions of the muscles to mix and propel the contents of the alimentary canal PAGEREF _Toc378015556 \h 27(c) describe digestion in the alimentary canal, the functions of a typical amylase, protease and lipase, listing the substrate and end-products PAGEREF _Toc378015557 \h 27(d) describe the structure of a villus and its role, including the role of capillaries and lacteals in absorption PAGEREF _Toc378015558 \h 28(e) state the function of the hepatic portal vein as the route taken by most of the food absorbed from the small intestine PAGEREF _Toc378015559 \h 28(f) state the role of the liver in: ? carbohydrate metabolism ? fat metabolism ? breakdown of red blood cells ? metabolism of amino acids and the formation of urea ? breakdown of alcohol PAGEREF _Toc378015560 \h 29(g) describe the effects of excessive consumption of alcohol: reduced self-control, depressant, effect on reaction times, damage to liver and social implications PAGEREF _Toc378015561 \h 295. Nutrition in Plants PAGEREF _Toc378015562 \h 30(a) identify and label the cellular and tissue structure of a dicotyledonous leaf, as seen in transverse section under the microscope and describe the significance of these features in terms of their functions, such as the: ? distribution of chloroplasts in photosynthesis ? stomata and mesophyll cells in gaseous exchange ? vascular bundles in transport PAGEREF _Toc378015563 \h 30(b) state the equation, in words and symbols, for photosynthesis PAGEREF _Toc378015564 \h 31(c) describe the intake of carbon dioxide and water by plants PAGEREF _Toc378015565 \h 31(d) state that chlorophyll traps light energy and converts it into chemical energy for the formation of carbohydrates and their subsequent storage PAGEREF _Toc378015566 \h 32(e) investigate and discuss the effects of varying light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis (e.g. in submerged aquatic plant) PAGEREF _Toc378015567 \h 33(f) discuss light intensity, carbon dioxide concentration and temperature as limiting factors on the rate of photosynthesis PAGEREF _Toc378015568 \h 346. Transport in Flowering Plants PAGEREF _Toc378015569 \h 35(a) identify the positions and explain the functions of xylem vessels, phloem (sieve tube elements and companion cells) in sections of a herbaceous dicotyledonous leaf and stem, under the light microscope PAGEREF _Toc378015570 \h 35(b) relate the structure and functions of root hairs to their surface area, and to water and ion uptake PAGEREF _Toc378015571 \h 35(c) explain the movement of water between plant cells, and between them and the environment in terms of water potential (Calculations on water potential are not required). PAGEREF _Toc378015572 \h 36(d) outline the pathway by which water is transported from the roots to the leaves through the xylem vessels PAGEREF _Toc378015573 \h 37(e) define the term transpiration and explain that transpiration is a consequence of gaseous exchange in plants PAGEREF _Toc378015574 \h 38(f) describe and explain: ? the effects of variation of air movement, temperature, humidity and light intensity on transpiration rate ? how wilting occurs PAGEREF _Toc378015575 \h 38(g) define the term translocation as the transport of food in the phloem tissue and illustrate the process through translocation studies PAGEREF _Toc378015576 \h 387. Transport in Humans PAGEREF _Toc378015577 \h 39(a) identify the main blood vessels to and from the heart, lungs, liver and kidney PAGEREF _Toc378015578 \h 39(b) state the role of blood in transport and defence ? red blood cells – haemoglobin and oxygen transport ? plasma – transport of blood cells, ions, soluble food substances, hormones, carbon dioxide, urea, vitamins, plasma proteins ? white blood cells – phagocytosis, antibody formation and tissue rejection ? platelets – fibrinogen to fibrin, causing clotting PAGEREF _Toc378015579 \h 40(c) list the different ABO blood groups and all possible combinations for the donor and recipient in blood transfusions PAGEREF _Toc378015580 \h 40(d) relate the structure of arteries, veins and capillaries to their functions PAGEREF _Toc378015581 \h 41(e) describe the transfer of materials between capillaries and tissue fluid PAGEREF _Toc378015582 \h 41(f) describe the structure and function of the heart in terms of muscular contraction and the working of valves PAGEREF _Toc378015583 \h 42(g) outline the cardiac cycle in terms of what happens during systole and diastole. (Histology of the heart muscle, names of nerves and transmitter substances are not required) PAGEREF _Toc378015584 \h 43(h) describe coronary heart disease in terms of the occlusion of coronary arteries and list the possible causes, such as diet, stress and smoking, stating the possible preventative measures PAGEREF _Toc378015585 \h 448. Respiration in Humans PAGEREF _Toc378015586 \h 45(a) identify on diagrams and name the larynx, trachea, bronchi, bronchioles, alveoli and associated capillaries PAGEREF _Toc378015587 \h 45(b) state the characteristics of, and describe the role of, the exchange surface of the alveoli in gaseous exchange PAGEREF _Toc378015588 \h 46(c) describe the removal of carbon dioxide from the lungs, including the role of the carbonic anhydrase enzyme PAGEREF _Toc378015589 \h 47(d) describe the role of cilia, diaphragm, ribs and intercostal muscles in breathing PAGEREF _Toc378015590 \h 47(e) describe the effect of tobacco smoke and its major toxic components – nicotine, tar and carbon monoxide, on health PAGEREF _Toc378015591 \h 48(f) define and state the equation, in words and symbols, for aerobic respiration in humans PAGEREF _Toc378015592 \h 48(g) define and state the equation, in words only, for anaerobic respiration in humans PAGEREF _Toc378015593 \h 48(h) describe the effect of lactic acid in muscles during exercise PAGEREF _Toc378015594 \h 499. Excretion in Humans PAGEREF _Toc378015595 \h 50(a) define excretion and explain the importance of removing nitrogenous and other compounds from the body PAGEREF _Toc378015596 \h 50(b) outline the function of kidney tubules with reference to ultra-filtration and selective reabsorption in the production of urine PAGEREF _Toc378015597 \h 51(c) outline the role of anti-diuretic hormone (ADH) in the regulation of osmotic concentration PAGEREF _Toc378015598 \h 51(d) outline the mechanism of dialysis in the case of kidney failure PAGEREF _Toc378015599 \h 5210. Homeostasis PAGEREF _Toc378015600 \h 53(a) define homeostasis as the maintenance of a constant internal environment PAGEREF _Toc378015601 \h 53(b) explain the basic principles of homeostasis in terms of stimulus resulting from a change in the internal environment, a corrective mechanism and a negative feedback PAGEREF _Toc378015602 \h 53(c) identify on a diagram of the skin: hairs, sweat glands, temperature receptors, blood vessels and fatty tissue PAGEREF _Toc378015603 \h 53(d) describe the maintenance of a constant body temperature in humans in terms of insulation and the role of: temperature receptors in the skin, sweating, shivering, blood vessels near the skin surface and the co-ordinating role of the hypothalamus PAGEREF _Toc378015604 \h 5411. Co-ordination and Response PAGEREF _Toc378015605 \h 55(a) state the relationship between receptors, the central nervous system and the effectors PAGEREF _Toc378015606 \h 55(b) describe the gross structure of the eye as seen in front view and in horizontal section PAGEREF _Toc378015607 \h 55(c) state the principal functions of component parts of the eye in producing a focused PAGEREF _Toc378015608 \h 56image of near and distant objects on the retina PAGEREF _Toc378015609 \h 56(d) describe the pupil reflex in response to bright and dim light PAGEREF _Toc378015610 \h 56(e) state that the nervous system – brain, spinal cord and nerves, serves to co-ordinate and regulate bodily functions PAGEREF _Toc378015611 \h 57(f) outline the functions of sensory neurones, relay neurones and motor neurones PAGEREF _Toc378015612 \h 57(g) discuss the function of the brain and spinal cord in producing a co-ordinated response as a result of a specific stimulus in a reflex action PAGEREF _Toc378015613 \h 58(h) define a hormone as a chemical substance, produced by a gland, carried by the blood, which alters the activity of one or more specific target organs and is then broken down by the liver PAGEREF _Toc378015614 \h 58(i) explain what is meant by an endocrine gland, with reference to the islets of Langerhans in the pancreas PAGEREF _Toc378015615 \h 58(j) state the role of the hormone adrenaline in boosting blood glucose levels and give examples of situations in which this may occur PAGEREF _Toc378015616 \h 59(k) explain how the blood glucose concentration is regulated by insulin and glucagon as a homeostatic mechanism PAGEREF _Toc378015617 \h 59(l) describe the signs, such as an increased blood glucose level and glucose in urine, and the treatment of diabetes mellitus using insulin PAGEREF _Toc378015618 \h 5912. Reproduction PAGEREF _Toc378015619 \h 61(a) define asexual reproduction as the process resulting in the production of genetically identical offspring from one parent PAGEREF _Toc378015620 \h 61(b) define sexual reproduction as the process involving the fusion of nuclei to form a zygote and the production of genetically dissimilar offspring PAGEREF _Toc378015621 \h 61(c) identify and draw, using a hand lens if necessary, the sepals, petals, stamens and carpels of one, locally available, named, insect-pollinated, dicotyledonous flower, and examine the pollen grains under a microscope PAGEREF _Toc378015622 \h 61(d) state the functions of the sepals, petals, anthers and carpels PAGEREF _Toc378015623 \h 62(e) use a hand lens to identify and describe the stamens and stigmas of one, locally available, named, wind-pollinated flower, and examine the pollen grains under a microscope PAGEREF _Toc378015624 \h 62(f) outline the process of pollination and distinguish between self-pollination and cross-pollination PAGEREF _Toc378015625 \h 63(g) compare, using fresh specimens, an insect-pollinated and a wind-pollinated flower PAGEREF _Toc378015626 \h 64(h) describe the growth of the pollen tube and its entry into the ovule followed by fertilisation (Production of endosperm and details of development are not required) PAGEREF _Toc378015627 \h 64(i) identify on diagrams of the male reproductive system and give the functions of: testes, scrotum, sperm ducts, prostate gland, urethra and penis PAGEREF _Toc378015628 \h 65(j) identify on diagrams of the female reproductive system and give the functions of: ovaries, oviducts, uterus, cervix and vagina PAGEREF _Toc378015629 \h 66(k) briefly describe the menstrual cycle with reference to the alternation of menstruation and ovulation, the natural variation in its length, and the fertile and infertile phases of the cycle with reference to the effects of progesterone and estrogen only PAGEREF _Toc378015630 \h 67(l) describe fertilisation and early development of the zygote simply in terms of the formation of a ball of cells which becomes implanted in the wall of the uterus PAGEREF _Toc378015631 \h 68(m) state the functions of the amniotic sac and the amniotic fluid PAGEREF _Toc378015632 \h 68(n) describe the function of the placenta and umbilical cord in relation to exchange of dissolved nutrients, gases and excretory products (Structural details are not required) PAGEREF _Toc378015633 \h 68(o) discuss the spread of human immunodeficiency virus (HIV) and methods by which it may be controlled PAGEREF _Toc378015634 \h 6913. Cell Division PAGEREF _Toc378015635 \h 70(a) state the importance of mitosis in growth, repair and asexual reproduction PAGEREF _Toc378015636 \h 70(b) explain the need for the production of genetically identical cells and fine control of replication PAGEREF _Toc378015637 \h 70(c) identify, with the aid of diagrams, the main stages of mitosis (e) identify, with the aid of diagrams, the main stages of meiosis PAGEREF _Toc378015638 \h 71(d) state what is meant by homologous pairs of chromosomes PAGEREF _Toc378015639 \h 72(f) define the terms haploid and diploid, and explain the need for a reduction division process prior to fertilisation in sexual reproduction PAGEREF _Toc378015640 \h 72(g) state how meiosis and fertilisation can lead to variation PAGEREF _Toc378015641 \h 7214. Molecular Genetics PAGEREF _Toc378015642 \h 73(a) outline the relationship between DNA, genes and chromosomes PAGEREF _Toc378015643 \h 73(b) state the structure of DNA in terms of the bases, sugar and phosphate groups found in each of their nucleotides PAGEREF _Toc378015644 \h 73(c) state the rule of complementary base pairing PAGEREF _Toc378015645 \h 74(d) state that DNA is used to carry the genetic code, which is used to synthesise specific polypeptides (details of transcription and translation are not required) PAGEREF _Toc378015646 \h 74(e) state that each gene is a sequence of nucleotides, as part of a DNA molecule PAGEREF _Toc378015647 \h 74(f) explain that genes may be transferred between cells. Reference should be made to the transfer of genes between organisms of the same or different species – transgenic plants or animals PAGEREF _Toc378015648 \h 74(g) briefly explain how a gene that controls the production of human insulin can be inserted into bacterial DNA to produce human insulin in medical biotechnology PAGEREF _Toc378015649 \h 75(h) discuss the social and ethical implications of genetic engineering, with reference to a named example PAGEREF _Toc378015650 \h 7515. Inheritance PAGEREF _Toc378015651 \h 76(a) define a gene as a unit of inheritance and distinguish clearly between the terms gene and allele PAGEREF _Toc378015652 \h 76(b) explain the terms dominant, recessive, codominant, homozygous, heterozygous, phenotype and genotype PAGEREF _Toc378015653 \h 76(c) predict the results of simple crosses with expected ratios of 3:1 and 1:1, using the terms homozygous, heterozygous, F1 generation and F2 generation PAGEREF _Toc378015654 \h 77(d) explain why observed ratios often differ from expected ratios, especially when there are small numbers of progeny PAGEREF _Toc378015655 \h 77(e) use genetic diagrams to solve problems involving monohybrid inheritance. (Genetic diagrams involving autosomal linkage or epistasis are not required) PAGEREF _Toc378015656 \h 77(f) explain co-dominance and multiple alleles with reference to the inheritance of the ABO blood group phenotypes – A, B, AB, O, gene alleles IA, IB and IO PAGEREF _Toc378015657 \h 78(g) describe the determination of sex in humans – XX and XY chromosomes PAGEREF _Toc378015658 \h 78(h) describe mutation as a change in the structure of a gene, such as in sickle cell anaemia, or in the chromosome number, such as the 47 chromosomes in the condition known as Down syndrome PAGEREF _Toc378015659 \h 78(i) name radiation and chemicals as factors which may increase the rate of mutation PAGEREF _Toc378015660 \h 79(j) describe the difference between continuous and discontinuous variation and give examples of each PAGEREF _Toc378015661 \h 79(k) state that competition which arises from variation leads to differential survival of, and reproduction by, those organisms best fitted to the environment PAGEREF _Toc378015662 \h 79(l) give examples of environmental factors that act as forces of natural selection PAGEREF _Toc378015663 \h 80(m) explain the role of natural selection as a possible mechanism for evolution PAGEREF _Toc378015664 \h 81(n) give examples of artificial selection such as in the production of economically important plants and animals PAGEREF _Toc378015665 \h 8116. Organisms and their Environment PAGEREF _Toc378015666 \h 83(a) briefly describe the non-cyclical nature of energy flow PAGEREF _Toc378015667 \h 83(b) explain the terms producer, consumer and trophic level in the context of food chains and food webs PAGEREF _Toc378015668 \h 83(c) explain how energy losses occur along food chains, and discuss the efficiency of energy transfer between trophic levels PAGEREF _Toc378015669 \h 83(d) describe and interpret pyramids of numbers and biomass PAGEREF _Toc378015670 \h 84(e) describe how carbon is cycled within an ecosystem PAGEREF _Toc378015671 \h 85(f) evaluate the effects of: ? water pollution by sewage and by inorganic waste ? pollution due to insecticides including bioaccumulation up food chains and impact on top carnivores PAGEREF _Toc378015672 \h 86(g) outline the roles of microbes in sewage disposal as an example of environmental biotechnology PAGEREF _Toc378015673 \h 87(h) discuss reasons for conservation of species with reference to the maintenance of biodiversity, management of fisheries and management of timber production PAGEREF _Toc378015674 \h 87THEME I: PRINCIPLES OF BIOLOGYOverviewA basic characteristic of life is the hierarchy of structural order within the organism. Robert Hooke (1635–1703), one of the first scientists to use a microscope to examine pond water, cork and other things, was the first to refer to the cavities he saw in cork as "cells", Latin for chambers. Subsequent scientists developed Hooke’s discovery of the cell into the Cell Theory on which modern Biology is built upon. The Cell Theory states that all organisms are composed of one or more cells, and that those cells have arisen from pre-existing cells.In this section, we study two key principles of biology. The first principle is the correlation of structure to function. This is illustrated by how each part of the cell is suited for its intended function. The second principle is that specialisation results in the division of labour which enables the cell to effectively carry out a number of vital life processes. A strong foundation in the principles of biology will pave the way for students to master the content in the subsequent topics.Extracted from BIOLOGY GCE ORDINARY LEVEL (2014) Syllabus Document1. Cell Structure and OrganisationContent? Plant and Animal Cells? Specialised Cells, Tissues and OrgansLearning Outcomes:Candidates should be able to:(a) identify cell structures (including organelles) of typical plant and animal cells from diagrams, photomicrographs and as seen under the light microscope using prepared slides and fresh material treated with an appropriate temporary staining technique: ? chloroplasts ? cell membrane ? cell wall ? cytoplasm ? cell vacuoles (large, sap-filled in plant cells, small, temporary in animal cells) ? nucleusCellsCells are the simplest units of lifeEach cell is made up of structures known as organelles for the cell to function#StructuresDescriptionDiagram1ChloroplastOvular structure with a double membraneMade of grana (stacks of discs) containing chlorophyll linked by thylakoid membranesFound only in plant cells2Cell membranePartially permeable membrane that surrounds the cytoplasm of the cellRefer to ‘Diagram of an entire plant cell’3Cell wallFully permeable wall made of cellulose surrounding the cell membraneFound only in plant cellsRefer to ‘Diagram of an entire plant cell’4CytoplasmJelly-like substance between the cell membrane and the nucleusRefer to ‘Diagram of an entire plant cell’5Cell vacuoleFluid-filled space enclosed by a membraneRefer to ‘Diagram of an entire plant cell’6NucleusSpherical or ovular structure with a double membrane, usually found at the centre of the cellMade of a nucleolus (a smaller-sized spherical structure) and DNA in the form of chromatin(b) identify the following membrane systems and organelles from diagrams and electron micrographs: ? endoplasmic reticulum ? mitochondria ? Golgi body ? ribosomes#StructuresDescriptionDiagram7Smooth endoplasmic reticulumTubular network of flattened spaces lined by a membraneConnected to rough endoplasmic reticulumDoes not have ribosomes attached to its outer membrane, unlike the rough endoplasmic reticiulum518795-3365500198755645795008Rough endoplasmic reticulumTubular network of flattened spaces lined by a membraneLess tubular than smooth endoplasmic reticulumConnected to smooth endoplasmic reticulumRibosomes are attached to its outer membrane, unlike the smooth endoplasmic reticiulum9MitochondrionSmall sausage-shaped structure surrounded by a double membraneThe inner membrane is folded inwards10Golgi bodyShaped like a discConsists of a stack of flattened spaces surrounded by membranesVesicles may fuse with or pinch off from the body11207756934200011RibosomeSmall round structureEither found attached to the rough endoplasmic reticulum or lies freely in the cytoplasmDiagram of an entire plant cellNote: Only study structures identified in the learning outcomes(c) state the functions of the membrane systems and organelles identified above#StructuresFunctions1ChloroplastAbsorbs sunlight to allow for the manufacture of food through photosynthesis2Cell membraneControls substances that leave and enter the cell3Cell wallGives the plant cell its fixed shape and protects it from injury4CytoplasmAllows cell activities to take place using organelles presentCatalyses biological reactions using enzymes present (e.g. breakdown of proteins into amino acids)5Cell vacuoleStores substances (e.g. water, mineral salts, amino acids) within cell6NucleusControl all cell activities within the cell (e.g. cell division, repair of worn out parts)7Smooth endoplasmic reticulumSynthesises fats and steriodsDetoxifies harmful substances (e.g. toxins)8Rough endoplasmic reticulumTransports proteins made by the cell ribosomes to the Golgi body for packaging9MitochondrionReleases energy for cell activities (e.g. growth and reproduction) through aerobic respiration of food substances10Golgi bodyStores, modifies and packages substances made by vesicles of the endoplasmic reticulum to be secreted out of the cell11RibosomeManufactures proteins to be either used within the cell or transported out of the cell(d) compare the structure of typical animal and plant cells#DifferencesAnimal cellsPlant cells1Shape of cellUsually irregularly shapedUsually regularly shaped2Presence of chloroplastsAbsentPresent3Presence of cell wallAbsentPresent4Presence of centriolesPresentAbsent5Presence of vacuoleTemporarily presentAlways present6Presence of sapAbsent in vacuolePresent in vacuole7Number of vacuolesSeveralSingle8Size of vacuolesSmallLargeAdditional informationSap contains various dissolved substances (e.g. sugars, mineral salts and amino acids)Centrioles are small hollow cylinders involved in cell divisionThe table above only lists differences present. Remember to include some similarities too!(e) state, in simple terms, the relationship between cell function and cell structure for the following: ? absorption – root hair cells ? conduction and support – xylem vessels ? transport of oxygen – red blood cells CellFunctionAdaptationsSignificanceRoot hair cellTo absorb water and dissolved mineral salts from soilLong and narrowIncreases surface area to volume ratioThis allows rate of absorption of water and dissolved mineral salts from soil to be increasedCell sap presentCell sap has less water potential than soilThis allows water to diffuse into the cell down a concentration gradientCell membrane present Prevents sap leakageThis maintains the abovementioned concentration gradientMitochondria presentRespires to release energy for the cellThis allows active transport to occur if the cell has a higher concentration of ions and mineral salts than soilXylem vesselTo conduct water and dissolved mineral salts from the roots to the stem and leavesLumen is long and hollowConducts water and dissolved mineral salts up the plant effectivelyCross walls and protoplasm absentLess obstructions enable water to flow more easily through the lumenThis maintains a continuous flowTo support the plant structureWalls are made of ligninStrengthens the walls of xylem vessels by providing mechanical support to the plantThis prevents the walls from collapsing Red blood cellTo transport oxygen from the lungs to all parts of the bodyCircular and biconcave shapeIncreases surface area to volume ratio of the cellThis allows oxygen can diffuse in and out of the entire cell at a faster rateNucleus absentAllows cell to carry more haemoglobin (since there is more space)This increases the rate at which oxygen is transported from the lungs to all parts of the bodyAble to change into a bell shapeDecrease in diameter enables them to move through lumens (with small diameters) easilyAlso increases surface area to volume ratio to speed up oxygen exchangeAdditional informationProtoplasm is made up of the cell membrane, cytoplasm and nucleus(f) differentiate cell, tissue, organ and organ systemLevelDescriptionExampleSmallestCellsCells are the simplest units of life Muscle cellTissuesCells of the same type group together to form a tissue, which performs a specific functionA muscle tissue is made of muscle cellsMuscle tissues allow various parts of the body to move by contracting and relaxingOrgansDifferent tissues group together to form an organ, which performs an overall functionThe stomach is made of muscular, glandular, connective and nervous tissuesThe various types of tissues work together so that the stomach can perform the overall function of storing, digesting and churning foodOrgan systemSeveral organs working together for a common purpose form an organ systemThe digestive system is made of various organs (e.g. stomach, intestines)LargestOrganismVarious organ systems work together to make up the entire organismThe human is made of various organ systems (e.g. digestive system, respiratory system)Use the knowledge gained in this section in new situations or to solve related problems2. Movement of SubstancesContent? Diffusion? Osmosis? Active TransportLearning Outcomes:Candidates should be able to:(a) define diffusion and discuss its importance in nutrient uptake and gaseous exchange in plants and humansTermDiffusionDefinitionNet movement of particles (i.e. atoms, ions or molecules)from a region where they are of higher concentrationto a region where they are of lower concentration(i.e. down a concentration gradient)ImportanceNutrient uptakeGaseous exchangeIn humansN.A.Oxygen from the air diffuses from the air sacs of lungs, where it is of higher concentration,into the red blood cells, where it is of lower concentrationLikewise, carbon dioxide from the organism diffuses from the red blood cells, where it is of higher concentration,into the air sacs of lungs, where it is of lower concentrationIn plantsWater and dissolved mineral salts diffuse via osmosis [will be discussed in the next learning outcome] from the soil, where it is of higher concentration,into the root hair cells, where it is of lower concentrationOxygen from the air diffuses from the soil, where it is of higher concentration,into the root hair cells, where it is of lower concentrationLikewise, carbon dioxide from the organism diffuses from the root hair cells, where it is of higher concentration,into the soil, where it is of lower concentration(b) define osmosis and discuss the effects of osmosis on plant and animal tissuesTermOsmosisWater potentialDefinitionMovement of water moleculesfrom a solution of higher water potential to a solution of lower water potentialthrough a partially permeable membraneRelative number of water molecules per unit volume of solutionMeasure of the tendency of water to move from one place to anotherScenarioIf a partially permeable membrane is placed betweena more dilute solution (more water molecules and less solute per unit volume) and a more concentrated solution (more solute and less water molecules per unit volume),water will move from the dilute solution to the concentration solutionEffects ofEntry of waterNo net movement of waterExit of waterOn animal cellsOn plant cellsEffects ofEntry of water (in dilute solution)Exit of water (in concentrated solution)On animal tissuesCells expand, swell and burstThis is because no cell wall is present to prevent cells from burstingTissue experiences loss of cellsCells shrink in size and crenate (i.e. little spikes appear on the cell membrane)Tissue becomes flaccidOn plant tissuesCells enlarge and become turgidThis is because the cell wall present prevents the cell from burstingTissue experiences increase in turgor pressureVacuole of cells shrinkCells plasmolyse (i.e. cytoplasm and cell membrane shrinks away from cell wall)Tissue becomes flaccidAdditional informationThe verbal form of movement of particles via osmosis is also ‘diffuse’ (i.e. there is no such thing as ‘osmosises’!)(c) define active transport and discuss its importance as an energy-consuming process by which substances are transported against a concentration gradient, as in ion uptake by root hairs and uptake of glucose by cells in the villiTermActive transportDefinitionProcess in which energy is usedto move the particles of a substancefrom a region where they are of lower concentrationto a region where they are of higher concentration(i.e. against a concentration gradient)ImportanceIon uptake by root hairsUptake of glucose by cells in the villiCaseOnly when root hair cells have a higher concentration of dissolved ions in water than soilOnly when villi of the small intestine have a higher concentration of glucose than soilDescriptionIons dissolved in water move via active transport from the soil, where it is of lower concentration,into the root hair cells, where it is of higher concentrationEnergy is consumed in the processGlucose moves via active transport from the chyme of digested material that passes, where it is of lower concentration,into villi of the small intestine, where it is of higher concentrationEnergy is consumed in the processUse the knowledge gained in this section in new situations or to solve related problemsDifferencesDiffusionOsmosisActive transportParticles movedParticles except water moleculesWater moleculesAll particlesType of gradientConcentrationWater potentialConcentrationDirection of transportDown gradientDown gradientAgainst gradientEnergy consumptionAbsentAbsentPresent3. Biological MoleculesContent? Water and Living Organisms? Carbohydrates, Fats and Proteins? EnzymesLearning Outcomes:Candidates should be able to:(a) state the roles of water in living organismsOrganism typeRolesAnimalsDigestive products can be transported from small intestine to body partsWaste products can be transported from tissue cells to excretory organs for removalHormones can be transported from glands to requiring parts of the bodyRegulates body temperature (i.e. when water in sweat evaporates, latent heat of vapourisation is removed)PlantsPhotosynthesisKeeps plant upright (i.e. water keeps plant cells turgid and firm)Mineral salts can be transported up the xylem from the roots to the leavesFood substances can be transported from the leaves to other plant parts(b) list the chemical elements which make up: ? carbohydrates ? fats ? proteinsNutrientCarbohydratesFatsProteinsCarbon PresentPresentPresentHydrogen PresentPresentPresentOxygen PresentPresentPresentNitrogenAbsentAbsentPresentSulfurAbsentAbsentMay be present(c) describe and carry out tests for: ? starch (iodine in potassium iodide solution) ? reducing sugars (Benedict’s solution) ? protein (biuret test) ? fats (ethanol emulsion) BiomoleculeTest nameProcedureCarbohy-dratesBenedict’s test Benedict’s solution is a solution containing blue copper (II) sulfateAdd 2cm3 of Benedict’s solution to 2 cm3 of the substance in a test tube Shake and leave the test tube in a beaker of boiling water for 5 minutes A green, yellow or brick-red precipitate (based on amount of reducing sugar) would be formed (i.e. traces, moderate amount and large amount of reducing sugar respectively)Iodine test When a few drops of potassium iodide is added to a substance containing starch, the iodine solution will turn from brown to blue-blackFatsEthanol emulsion testA cloudy white emulsion (i.e. a suspension of small drops of liquid in another liquid) is formed when ethanol and water are added to fatsIf tested on solid food, the food has to be cut up into many small pieces and added with 2cm3 ethanolAfter shaking and allowing the solid particles to settle, decant the ethanol into another test tube with 2cm3 of water, a cloudy white emulsion is formed if the food contains fatProteinsBiuret testBiuret solution is made up of sodium hydroxide and copper (II) sulfateWhen 2cm3 of the substance is added and stirred with 2cm3 of biuret solution, the solution turns from blue to violet if the substance contains protein(d) state that large molecules are synthesised from smaller basic units: ? glycogen from glucose ? polypeptides and proteins from amino acids ? lipids such as fats from glycerol and fatty acidsLarge moleculeSynthesis (enzyme not required)CarbohydratesStarch Many glucose molecules Maltose Many maltose molecules StarchGlycogen Many glucose molecules GlycogenProteinMany amino acids PolypeptidesMany polypeptides ProteinsFatGlycerol + 3 Fatty acid Fat + 3 Water Large moleculeBreakdown (enzyme required)EnzymeStarchStarch Many maltose moleculesAmylase Maltose Many glucose moleculesMaltaseProteinProteins Many polypeptidesPepsin (protease)Polypeptides Many amino acidsErepsin (protease)FatFat + 3 Water Glycerol + 3 Fatty acidLipase(e) explain enzyme action in terms of the ‘lock and key’ hypothesisTermsDefinitionsRelation to ‘lock and key’EnzymeProtein that speeds up the rate of a biological reactionLockSubstratesSubstances on which enzymes actKey (that fits into the lock)Active site of enzymeSmall portion of the enzyme that comes into direct contact with the substratesGroove (of the lock)DiagramExplanationThe substrates have shapes that are complementary to the active site of the enzymeThus the substrates are able to fit into the active site of enzymeThis allows the reaction to take placeThis is similar to a key that is inserted into a lock, based on the ‘lock and key’ hypothesisThe key will only be able to open the lock if it is complementary in shape and fits into the grooves of the lock(f) explain the mode of action of enzymes in terms of an active site, enzyme-substrate complex, lowering of activation energy and enzyme specificityKey questionExam responseWhat are enzymes?An enzyme is a protein that speeds up the rate of a specific biological reactionWhat is the structure of enzymes that helps them achieve their role?Each enzyme has an active site, which is a small portion of the enzyme that comes into direct contact with the substratesHow do enzymes achieve their role?Collision between substrates and enzyme at the correct orientationcauses the substrate to bind to the enzyme at its active siteto form an enzyme-substrate complexThis increases the likelihood of bond breaking/forming,which lowers the activation energy of the reaction (the minimum energy needed to start the reaction)thus speeding up the rate of the reaction(g) investigate and explain the effects of temperature and pH on the rate of enzyme catalysed reactionsTermDefinitionDenaturationRandom unlooping of the 3D structure of a protein or enzyme FactorOptimum levelEffects of changes from optimumDiagramTempe-ratureAt optimum temperature, the enzyme is most activeas high kinetic energy supplied causes more collisions between enzyme and substrate moleculesand vibrations in protein atoms are not high enough to denature the enzymeAs temperature decreases from optimum,the kinetic energy supplied to the reacting molecules decreasesThis causes less frequent collisions between the substrate and enzyme molecules,decreasing the chance of substrates fitting into active sitesRate of formation of products thus decreases graduallyAs temperature increases from optimum,vibrations in the atoms of the enzyme become more violentThis breaks the hydrogen bonds of protein within the enzymesThe enzyme loses its specific shape and denaturesRate of formation of products thus decreases steeplypHSome enzymes work best in slightly acidic solutionswhile others require slightly alkaline solutionsExtreme changes in acidity or alkalinity of the solutions denature the enzymesThe first reason is that hydrogen bonds of protein within the enzymes are brokenThe second reason is that most substrates and enzymes have opposite electrostatic charges that allow them to bindThe extreme changes alter the charges on the substrate and enzymes such that they bind less wellUse the knowledge gained in this section in new situations or to solve related problemsTHEME II: MAINTENANCE AND REGULATION OF LIFE PROCESSESOverviewLife is sustained through the integrated organisation of the whole organism. In humans, themaintenance and regulation of life processes include nutrition, transport, respiration, excretion,homeostasis and co-ordination and response. The key overarching theme in the study of the organsystems is the correlation between form and function.Extracted from BIOLOGY GCE ORDINARY LEVEL (2014) Syllabus Document4. Nutrition in HumansContent? Human Alimentary Canal? Chemical Digestion? Absorption and AssimilationLearning Outcomes:Candidates should be able to:(a) describe the functions of main regions of the alimentary canal and the associated organs: mouth, salivary glands, oesophagus, stomach, duodenum, pancreas, gall bladder, liver, ileum, colon, rectum, anus, in relation to ingestion, digestion, absorption, assimilation and egestion of food, as appropriate#RegionFunctionDescription of function1MouthIngestionHas teeth which chews to break down large pieces of food into smaller pieces to increase surface area to volume ratio of food lumps2Salivary glandIngestionSecretes saliva containing mucin which softens the food so that swallowing the food lumps is easierDigestionSecretes saliva containing salivary amylase is secreted by salivary glands through salivary ducts into the mouth, which digests some starch into maltose3OesophagusDigestionInduces peristalsis (along with other parts of the alimentary canal) that allows food to be mixed with digestive juices easily and broken down further through churning, increasing rate of collision of enzymes and substrates and rate of digestion4StomachDigestion[Initial process] Secretes gastric juice to convert pepsinogen to pepsin, and prorennin to rennin [Eventual process] Secretes gastric juice containing hydrochloric acid which provides a suitable pH for pepsin to digest proteins to polypeptides, and rennin to turn soluble milk proteins insoluble so that it can be fully digested before moving to small intestine [Combination of the above processes] Digestion in the stomach turns the partly digested food into liquified chyme, enabling food to pass into the duodenum in small amounts instead of altogether increasing surface area to volume ratio and giving small intestine more time to digest5DuodenumDigestionSecretes intestinal juice1. Carbohydrases: Maltase converts maltose to glucose2. Proteases: Erepsin digests polypeptides to amino acids6PancreasDigestionSecretes pancreatic juice1. Amylase: Pancreatic amylase digests starch to maltose 2. Lipase: Pancreatic lipase digests fats to fatty acids and glycerol3. Proteases: Trypsin converts remaining protein to polypeptidesAssimilationSecretes the hormone glucagon to stimulate the liver to convert glycogen into glucose when blood glucose concentration is low, and transported to the cells and oxidised to produce more energy#RegionFunctionDescription of function7Gall bladderDigestionStorage and release area of bile from the liver, assisting emulsification8LiverDigestionSecretes bile released from gall bladder to emulsify fats1. Lower surface tension of fats2. Smaller fat droplets3. Lipase digests fats fasterAssimilationCarries out deamination of excess amino acids by converting part of it to glucose that can be used to provide more energyEgestionCarries out deamination of excess amino acids by converting part of it to ureaBreaks down haemoglobin from red blood cells to be converted into bile9IleumAbsorptionBlood capillaries transport sugars and amino acids to the hepatic portal veinLacteals transport minute fat globules of glycerol and fatty acids to lympatic vesselsHepatic portal veinAbsorptionTransports sugars and amino acids to the liver to convert excess of them into glycogen and urea, then distributing remaining to the body partsLymphatic vesselsAbsorptionTransports small fat globules to the bloodstream to be distributed to the rest of the body10ColonAbsorptionWater and mineral salts absorbedEgestionControls emptying of the rectum11RectumEgestionIntestinal wall secretes mucus that lubricates undigested contents, which stays for 36 hours12AnusEgestionStores undigested food as faeces temporarily#ProcessIngestionDigestionAbsorptionAssimilationEgestion1Mouth2Salivary gland3Oesophagus4Stomach5Duodenum6Pancreas7Gall bladder8Liver9Ileum10Colon11Rectum12AnusDiagram(b) describe peristalsis in terms of rhythmic wave-like contractions of the muscles to mix and propel the contents of the alimentary canalTermDefinitionPeristalsisRhythmic wave-like contractions of muscles of the gutPeristalsic actionFunctionMixes food well with digestive juices easilyIncreases rate of collision of enzymes and substrates and rate of digestionPropel food down the gutPushing of food from behind down the gut By contracting of internal circular muscles and relaxing external longitudinal muscles, which constricts the lumenProviding space for food in front to move down the gutBy relaxing of internal circular muscles and contracting external longitudinal muscles in front of the food provides space for food to move forward easilyChurning to create chymeEnables food to pass into the duodenum in small amounts instead of altogether, giving small intestine more time for digestionDiagram(c) describe digestion in the alimentary canal, the functions of a typical amylase, protease and lipase, listing the substrate and end-productsLarge moleculeEnzymeSubstrateEnd-productsCarbohydratesAmylase Starch Maltose ProteinsProteasesPepsinPolypeptidesProteins ErepsinAmino acidsPolypeptidesFatsLipaseGlycerol + Fatty acidsFat + Water (d) describe the structure of a villus and its role, including the role of capillaries and lacteals in absorptionRegion in small intestineRoleVillusHighly folded with microvilli (in-foldings) to increase surface area to volume ratio for faster rates of absorptionBlood capillariesTransports sugars and amino acids to the hepatic portal veinLactealsTransports minute fat globules of glycerol and fatty acids to lympatic vesselsAdaptation of small intestineSignificanceHighly folded with villi and microvilli of finger-like structuresIncreases surface area to volume ratio for faster rates of absorptionEpithelial wall is one cell thinDecreases time needed for food molecules to travel through the wall, increasing rate of absorption Long and making up 60% of the small intestineEnsures sufficient time for complete absorptionMany capillaries in intestinal wall and villi transports food molecules away from intestineMaintains concentration gradient of digested food substances through epithelial wall(e) state the function of the hepatic portal vein as the route taken by most of the food absorbed from the small intestineRegionFunctionHepatic portal veinRoute taken by most of the food absorbed from the small intestine to be distributed to other body partsRoute of food taken from small intestine to other body parts(f) state the role of the liver in: ? carbohydrate metabolism ? fat metabolism ? breakdown of red blood cells ? metabolism of amino acids and the formation of urea ? breakdown of alcohol#Roles of liverDescription of roles of liver1Carbohydrate metabolismInsulin produced by the islets of Langerhans of the pancreas stimulates the liver to convert glycogen to glucoseand converts glucose back to glycogen by glucagon and adrenalin if the concentration ratio of glucose is high to regulate blood glucose concentration2Fat metabolismSecretes bile containing bile salts and bile pigments that emulsify fats,enabling it to turn into more, smaller droplets with high surface area to volume ratio and lower surface tension,increasing the digestion rate between fats and water into fatty acids and glycerol by lipase3Breakdown of red blood cellsHaemoglobin in red blood cells is broken down into iron and bile salts to be excreted out of the body through faeces4Amino acid metabolismDeanimates amino acids and converts part of them into glycogen, to be stored in liver and muscles that can convert it to glucose of blood glucose level is lowThe other part will be converted to urea, to be excreted through urine5Breakdown of alcoholAlcohol dehydrogenase from liver breaks down alcohol into acateldahyde compounds that can be broken down during respiration to release energyHowever, if alcohol used excessively, acids are secreted in the stomach that might cause gastric ulcersIn worser cases, cirrhosis will destroy liver cells, diminishing its function(g) describe the effects of excessive consumption of alcohol: reduced self-control, depressant, effect on reaction times, damage to liver and social implications#EffectsDescription of effects of excessive alcohol consumption1DepressantAlcohol inhibits the function of the central nervous system by disrupting the brain’s communication pathways2Reduced self-controlAs a result, it is more difficult for the person to think clearly and move with coordination3Effect on reaction timesIt also takes a longer time for the person to process informationFor example, the slower rate of reaction to sudden changes in traffic to makes it easier for drivers to cause an accident4Damage to liverLiver inflammations may occurFor example, cirrhosis will destroy liver cells, diminishing its function5Social implications HYPERLINK "" \l "sthash.dF0kKMzn.dpuf" Furthermore, excessive alcohol use can effect all areas of a person's life, including family, work and personal relationships1. Family problems: Arguments over someone's drinking can cause family and relationship problems that may lead to break up2. Work problems: Drinking alcohol at work and hangovers can lead to poor performance and accidents at work, while illness can result in absenteeism3. Legal problems: Drink-driving may lead to fines, loss of license and even imprisonmentSource: the knowledge gained in this section in new situations or to solve related problems.5. Nutrition in PlantsContent? Leaf Structure? PhotosynthesisLearning Outcomes:Candidates should be able to:(a) identify and label the cellular and tissue structure of a dicotyledonous leaf, as seen in transverse section under the microscope and describe the significance of these features in terms of their functions, such as the: ? distribution of chloroplasts in photosynthesis ? stomata and mesophyll cells in gaseous exchange ? vascular bundles in transportFeaturesAspectsSignificanceDistribution of chloroplasts in photosynthesisPalisade mesophyll cellsContains numerous chloroplasts, located right below the upper epidermis and closely packed togetherto absorb maximum sunlight for photosynthesisSpongy mesophyll cellsContains chloroplaststo maximise photosynthesis of plantStomata and mesophyll cells in gaseous exchangeIncrease stomatal receival of carbon dioxideIn sunlight, photosynthesis occursEnergy is used to pump potassium ions into the guard cells, increasing K+ concentration and decreasing water potential of guard cells, causing water to enter these guard cells by osmosisThis turns them turgid and pulls stomata open, resulting in more carbon dioxide received to facilitate higher photosynthesis rates under sunlightDecrease stomatal loss of water vapourAt night, K+ ions accumulated in the day diffuse out of the guard cells, increasing water potential and causing water to leave the guard cells through osmosisAs the cells are more flaccid, the stomatal pore closesUnder high temperature, excess evaporation (transpiration) of water causes the guard cells to be more flaccid, closing the stomatal pore.All mesophyll cells (carbon dioxide and oxygen)Covered with a thin film of water for gasesto dissolve in to allow rapid diffusion of carbon dioxide and oxygen in and out of the mesophyll cellsSpongy mesophyll cellsIrregular with large intercellular air spaces among them to allow rapid diffusion of gases from stomata to the vascular bundles through the leafVascular bundles in transportXylem (top) for loss of water vapourTransports water and dissolved mineral salts from the roots to the leaf so that once out of the xylem, the water and mineral salts move from cell to cell right through the mesophyll of the leaf by osmosisPhloem (bottom) for transport of sugars When the mesophyll cells receive water from xylem and carbon dioxide from the air through the stomata, they can manufacture food under light by photosynthesis, in which the phloem will transport sugars to other plant partsEpidermal layerCuticle of the upper and lower epidermisClosely packed with waxy cuticle that prevents excessive evaporation (transpiration) of waterTransparent to allow sunlight to penetrate the leaf easilyDiagram(b) state the equation, in words and symbols, for photosynthesisEquation for photosynthesisIn wordsCarbon dioxide+WaterGlucose+OxygenIn symbols6 CO2+6 H2OC6H12O6+6 O2(c) describe the intake of carbon dioxide and water by plantsProcessesDescription of processesPhotosynthesisPhotosynthesis occurs whenever there is sunlightWater potentialEnergy is used to pump potassium ions into the guard cells, increasing K+ concentration and decreasing water potential of guard cells, causing water to enter these guard cells by osmosisTurgidity of guard cellsThis turns them turgid and pulls stomata open, resulting in more carbon dioxide (and water vapour) received to facilitate higher photosynthesis rates under sunlight(d) state that chlorophyll traps light energy and converts it into chemical energy for the formation of carbohydrates and their subsequent storageSubstanceFunctionChlorophyllTraps light energy and converts it into chemical energy for the formation of carbohydrates via photosynthesis and their subsequent storage as starchComponents of photosynthesisSignificanceReactants (raw materials)Carbon dioxideProduced by all living organisms during respiration are removed in photosynthesis for plants to produce food WaterRequired to produce glucose as it contains the hydrogen elementActivation energyChlorophyll traps light and converts it to chemical energyChemical energy would be used to start the photochemical reaction to convert carbon dioxide and water to glucose and oxygenEnd-productsGlucoseTransported through the phloem to various parts of the plant by translocationUsed as a reactant of respiration to release energy for cellular activities in the plantSucroseExcess glucose produced in the leaf is converted to sucrose and transported to storage organs (e.g. seeds)StarchExcess glucose produced in the leaf is converted to starch to be stored temporarily, converted back mostly at night when photosynthesis stopsOxygenOxygen is produced and used by all organisms in respiration, allowing them to release energy(e) investigate and discuss the effects of varying light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis (e.g. in submerged aquatic plant)#FactorsEffects1Light intensityWhen light intensity increases, the rate of photosynthesis generally increasesWhen light intensity is at light compensation pointRate of photosynthesis is equal rate of respiration (i.e. rate of carbon dioxide intake is equal to that of oxygen)Any rise in light intensity after this point will cause rate of photosynthesis to be greater than rate of respirationWhen light intensity is at light saturation pointRate of photosynthesis is maximumAny rise in light intensity after this point will not affect rate of photosynthesis (i.e. rate of photosynthesis remains constant)2Carbon dioxide concentrationWhen carbon dioxide concentration increases, the rate of photosynthesis generally increasesThis is because carbon dioxide is a key reactant in photosynthesisRate of photosynthesis remains constant eventually as carbon dioxide concentration rises further3TemperatureWhen temperature increases up to 40oC, the rate of photosynthesis increasesThis is because enzymes involved in photosynthesis are more activeWhen temperature is increases beyond 40°C, the rate of photosynthesis dropsThis is because enzymes involved in photosynthesis are denatured(f) discuss light intensity, carbon dioxide concentration and temperature as limiting factors on the rate of photosynthesisTermDefinitionClarificationLimiting factorThe factor that directly increases the rate of a process if its quantity is increasesand is the lowest in concentration among all other factorsWhile a process can be affected by many factors, only one of the factors can be the limiting factor at any given time (i.e. the one that is lowest in concentration)#FactorsWhen the factor is limitingGraph1Light intensityWhen light intensity increases, the rate of photosynthesis generally increasesIn this case, light intensity is the limiting factorAt light saturation point, rate of photosynthesis is maximum and cannot increase furtherIn this case, either carbon dioxide or temperature replaces light intensity as the limiting factor2Carbon dioxide concentrationCarbon dioxide is an important limiting factor as it makes up only 0.03% of airIt ceases to be the limiting factor when rate of photosynthesis is maximum3TemperatureWhen light intensity is low, temperature cannot be a limiting factorWhen light intensity is high, temperature is a likely limiting factorTemperature ceases to be the limiting factor when rate of photosynthesis starts to fallRelationship between the above-mentioned factorsUse the knowledge gained in this section in new situations or to solve related problems6. Transport in Flowering PlantsContent? Water and Ion Uptake? Transpiration and TranslocationLearning Outcomes:Candidates should be able to:(a) identify the positions and explain the functions of xylem vessels, phloem (sieve tube elements and companion cells) in sections of a herbaceous dicotyledonous leaf and stem, under the light microscopePlant partsFunctionsXylemTransport mineral salts and waterthrough lignified walls, which provide mechanical strength to the plantsPhloemAllows water to move efficientlyby not having cross walls, which maintains a continuous lumenSieve tube elementsProtoplasm of the sieve tube is disintegrated and the sieve plate walls contain holes,allowing rapid movement of food from the leaves due to less obstructionsCompanion cellsContain mitochondria to release energy neededfor active transport of food from the leaves to other parts of the plantDiagramsXylem and phloem in leafXylem and phloem in stemNote: Xylem is shaded in the diagrams while phloem is not(b) relate the structure and functions of root hairs to their surface area, and to water and ion uptakeStructureFunctionLong and narrow(surface area)Increases surface area to volume ratioto allow rate of absorption of mineral salts and water to be increasedContains cell sap(water uptake)Cell sap has less water potential than soilto allow water to diffuse into the cell down a concentration gradientMitochondria present(ion uptake)Releases energy during respiration for the cellto allow active transport to occur if the cell has a higher concentration of ions and mineral salts(c) explain the movement of water between plant cells, and between them and the environment in terms of water potential (Calculations on water potential are not required).DirectionMovementExplanationFrom soil to root hair cellEither:Water molecules move from the soil water across the partially permeable cell membrane into the root hair cell by osmosisThis occurs if there is a higher water potential in soil water than the root hair cellOr:Root hair cell absorbs water molecules from the soil water across the partially permeable cell membrane by active transportThis occurs if there is a lower water potential in soil water than the root hair cell (energy from cell respiration is used for active transport)From root hair cell to cortex cell besideWater molecules move from the root hair cell into the cortex cell by osmosisThe root hair cell has higher water potential than the cortex cell beside itFrom the series of cortex to xylem vesselThe above movement of water continues from cell to cell through the series of neighbouring cortex cells until the water molecules reach the xylem tissue in the rootWater molecules travel up the xylem through transpiration pull to the leavesXylem vessel of leaves to thespongy mesophyll cellWater molecules move from the xylem tissue to the mesophyll cells by osmosis There is a higher water potential in xylem tissue in the leaf than the mesophyll cellsWater evaporates from the mesophyll cells Water forms a thin film of moisture over the mesophyll surfaces and turns into water vapourSpongy mesophyll cell to atmosphereWater moves from the thin film of moisture into the intercellular air spaces, accumulating in the air spaces that are near the stomataWater vapour diffuses through the stomata to the drier air outside the leaf through transpiration(d) outline the pathway by which water is transported from the roots to the leaves through the xylem vesselsOutlineDiagram(e) define the term transpiration and explain that transpiration is a consequence of gaseous exchange in plantsTermDefinitionExplanationTranspirationThe loss of water vapour from the aerial parts of a plant, especially through the stomata of the leavesAs water vapour evaporates from the film of water on the spongy mesophyll cells, the water potential of the cell sap decreasesThe mesophyll cells then absorb water by osmosis from the xylem vessels deep inside the leaf, removing water from the xylem vesselsA suction force results, pulling the whole column of water up the xylem vesselsThus transpiration is a consequence of gaseous exchange(f) describe and explain: ? the effects of variation of air movement, temperature, humidity and light intensity on transpiration rate ? how wilting occurs#FactorEffectExplanation1Air movementAs increase in air movement increases transpiration rateWind blows away water vapour that accumulates outside the stomata, increasing water vapour concentration gradient2Temperature of airAn increase in temperature increases transpiration rateRate of evaporation increases as temperature increases3Humidity of airAn increase in humidity decreases transpiration rateIntercellular air spaces are normally saturated with water vapourIncrease in humidity (water vapour in the air) decreases the water vapour concentration gradient4Light intensityAn increase in light intensity increases transpiration rateAs light increases, the size of the stomata on the leaf increases and widensTermDescriptionExplanationAdvantageDisadvantageWiltingLoss of rigidity of non-woody parts of plants due to loss of turgorAny of above factors can cause rate of transpiration to be more than that of absorptionCells lose turgor due to loss of water and therefore wiltsReduces transpirationLeaf folds up, reducing surface area exposed to lightGuard cells become flaccid and stomata closeReduces rate of photosynthesisWhen stomata close, amount of carbon dioxide entering plant is reduced, which becomes the limiting factorWhen folded, surface area is reduced, causing light received to be limited(g) define the term translocation as the transport of food in the phloem tissue and illustrate the process through translocation studiesTermDefinitionIllustrationTranslocationTransport of manufactured food substances such as sugars and amino acids in phloem tissuesWhen the mouthpart of an aphid penetrates a leaf or stem, anaesthetise it with carbon dioxide while it is feedingCut off body of aphid and analyse liquid from the cut end of mouthUse the knowledge gained in this section in new situations or to solve related problems.7. Transport in HumansContent? Circulatory SystemLearning Outcomes:Candidates should be able to:(a) identify the main blood vessels to and from the heart, lungs, liver and kidney Circulatory systemDiagram2243455-788100(b) state the role of blood in transport and defence ? red blood cells – haemoglobin and oxygen transport ? plasma – transport of blood cells, ions, soluble food substances, hormones, carbon dioxide, urea, vitamins, plasma proteins ? white blood cells – phagocytosis, antibody formation and tissue rejection ? platelets – fibrinogen to fibrin, causing clotting#Components of bloodFeaturesFunctions1Red blood cellsHaemoglobinOxygen is being transported by haemoglobin in red blood cellsAbsence of nucleus allows space for haemoglobin which combines reversibly with oxygen, binding easily with oxygen to carry it in blood and unbinding to release oxygen to requiring partsOxygen transportCircular and biconcave shape increases surface area to volume ratio and thus rate of absorption and release of oxygenElasticityAble to turn into a bell shape, allowing it to squeeze through blood vessels of diameter smaller than itself, easing movement through lumen and increasing surface area to volume ratio to speed up oxygen exchange2PlasmaTransport of substances within bodyTransports substances like blood cells, soluble food substances, plasma proteins, water, ions, carbon dioxide, vitamins, hormones and urea around the body3White blood cellsPhagocytosisPhagocytes engulf and ingest pathogens and harmful foreign bacteriaAntibody formationLymphocytes produce antibodies that clump foreign bacteria together, protecting the body against fatal bacteria and virusesTissue rejectionLymphocytes produce antibodies to destroy foreign organs, as organs from another person are usually treated as a foreign body by his immune system4PlateletsBlood clottingWhen tissues are damaged, enzymes released from platelets convert prothrombin to thrombin so that fibrinogen can be converted to insoluble fibrin, meshing up to trap blood cells, preventing them from flowing out(c) list the different ABO blood groups and all possible combinations for the donor and recipient in blood transfusionsBlood groupComponentsCombinations for donor and recipientImportanceAntigensAntibodiesGive blood toReceive blood fromABA, B-ABA, B AB, OFailure to abide by the guidelines of giving and receiving blood will result in agglutinationAABA, ABA, OBBAB, ABB, OO-A, BA , B, AB, OO(d) relate the structure of arteries, veins and capillaries to their functionsVesselsStructureFeaturesFunctionsArteries131762567564000146367519812000Small lumen sizeAt higher pressure this allows fast rate of flow of blood to body partsElasticTo withstand high pressure from the small lumen size and recoil for blood to travel in spurts under the high pressureMuscularEnables artery to dilate and constrict by the relaxation and contraction of muscles of arterial wallVeinsSemi lunar valves presentTo prevent the backflow of bloodParts of vein are found alongside skeletal musclesContracting of skeletal muscles during exercise compresses the vein, exerting more pressure and pushing blood flow forward at a faster rateCapillariesSmall lumen of arteries and large lumen of veinsHigher pressure of the arteries and lower pressure of the veins allow constant flow of blood through the capillariesEndothelium partially permeableEnables certain substances to diffuse quickly through the capillary wallsCapillaries branch repeatedlyIncreases cross sectional area, lowers blood pressure, slows flow of blood, increases time for exchange of substances(e) describe the transfer of materials between capillaries and tissue fluidKey questionExam responseHow is tissue fluid is formed?High pressure at the arterial end of capillaries force out diluted blood plasma and white blood cells, giving rise to tissue fluidWhich substances are transported from the capillaries?Dissolved food substances and oxygen are transported from the blood in blood capillaries, into the tissue fluid, then to the tissue cells Which substances are transported into the capillaries?Excretory waste products diffuse from the tissue cells into the tissue fluid, then to the blood, to be transported to excretory waste organs Diagram1508760127205700(f) describe the structure and function of the heart in terms of muscular contraction and the working of valvesStructureFunctionMedian septumDivides the heart to the left side and the right side, separating both sides so that blood flows in only one direction as oxygenated and deoxygenated blood do not mix togetherChamber valvesTricuspid, bicuspid and semi lunar valves prevent the blood from flowing backwards, ensuring that blood flows in only one directionChordae tendineaeAttached to the wall of ventricles to prevent the flaps of the valves from inverting during ventricular contractionVentricles thicker muscular walls than atriaVentricles would be able to pump blood a longer distance to ease the pumping of blood out of the heart (since blood leaves the heart via the ventricles)Left ventricle thicker muscular walls than right ventricleRight ventricle able to pump blood at a lower pressure along a small distance, ensuring that the slow rate of blood flow allows sufficient time for gaseous exchange at the lungs (unlike left ventricle that pumps blood around the body)Diagram(g) outline the cardiac cycle in terms of what happens during systole and diastole. (Histology of the heart muscle, names of nerves and transmitter substances are not required)HappeningsAtrial SystoleVentricular SystoleVentricular DiastoleAtriaContract [1] Relax Relax VentriclesRelax Contract Relax [3] Blood FlowFrom atria to ventricles From ventricles to aorta and pulmonary artery From vena cava and pulmonary veins to atria PressureVentricular pressure increases Pressure in ventricle higher than aorta Ventricular pressure decreases Tricuspids and BicuspidsOpen Close (“lub” produced) Open [4] Semi-Lunar ValvesClosed Forced open [2] Close (“dub” produced) Diagram(h) describe coronary heart disease in terms of the occlusion of coronary arteries and list the possible causes, such as diet, stress and smoking, stating the possible preventative measuresCoronary arteriesCoronary heart disease (CHD)FunctionSignificanceExplanationCoronary arteries lie on the outside of the heart and carry blood to muscles in the walls of the heartHeart muscles must be supplied with oxygen and nutrients via blood in order to pump blood around the bodyBlocked or narrowed coronary arteries reduces blood supply to the walls of the heart greatlyThis causes the supply of oxygen and nutrients to the muscles in the walls of the heart to be insufficientHeart will not be able to pump blood around the bodyCauses of CHDDescription of causes of CHDCholesterol metabolismA diet rich in cholesterol and saturated animal fats causes fatty substances like cholesterol to be deposited on the inner surface of coronary arteriesSize of lumenNarrowed lumen increases blood pressure from rough inner artery surfacesBlood clotsRisk of blood clots being trapped in the coronary arteries via thrombosisInsufficient supply of oxygenSupply of blood and oxygen may be insufficient, resulting in insufficient energy released to heart musclesEmotional stress and smoking increases the risk of atherosclerosisMeasuresDescription of measures to prevent CHDProper dietUse of polyunsaturated plant fats and dietary fibres will lower cholesterol level in bloodProper stress managementReduces risk of a heart attack as people with high stress levels tend to require more oxygen levelsDecrease or stop smokingNicotine increases blood pressure and risk of blood clotting Carbon monoxide increases risk of fatty depositsRegular physicalexerciseStrengthens the heart and maintains elasticity of arteriole walls, reducing high blood pressureUse the knowledge gained in this section in new situations or to solve related problems8. Respiration in HumansContent? Human Gas Exchange? Aerobic Respiration? Anaerobic RespirationLearning Outcomes:Candidates should be able to:(a) identify on diagrams and name the larynx, trachea, bronchi, bronchioles, alveoli and associated capillariesDiagrams103437180010Larynx00Larynx1046524666750Trachea00Trachea927735955719Bronchus00Bronchus16002001691640Bronchioles00Bronchioles1831975100330Alveoli00Alveoli791845159385Bronchiole00Bronchiole17710151163955Capillaries00Capillaries1555750311785001604010308610001573530998220001712595139255500102044536258500(b) state the characteristics of, and describe the role of, the exchange surface of the alveoli in gaseous exchangeCharacteristicsAdaptationRelation to roleRich supply of blood capillariesEnsures a constant concentration gradient of gas moleculesHelps the lungs ensure continuous uptake of oxygen for respiration in order to release energy...Thin film of moisture on internal surface of alveoli Allows oxygen to dissolve and diffuse into the alveoli easily... by being specially adapted for rapid transfer of gases between the lungs and the blood capillariesLarge surface area of alveoliFaster rate of diffusion of gases with high surface area to volume ratioOne cell thick wall of alveoliShorter distance for gas molecules to diffuse across it increases rate of diffusion and efficiencyDiagrams86734264219800-332520919890014374162092362003892219250210 (c) describe the removal of carbon dioxide from the lungs, including the role of the carbonic anhydrase enzymeRelationProcessesDescriptionFormation of carbon dioxideInspirationOxygen is taken in through the nose and diffuses from the alveoli in lungs to blood capillaries heading to the heartOxygen leaves alveoliAfter leaving the lungs and the heart, oxygen is distributed to tissue cells for respirationRespirationGlucose reacts with oxygen to produce carbon dioxide and waterRemoval of carbon dioxideCarbon dioxide leaves the capillaries of tissue cellsAcidification in red blood cellWater and carbon dioxide react to form carbonic acid with the help of the enzyme carbonic anhydraseDeassociation, entry to plasmaCarbonic acid is converted to hydrogen and carbonate ions (hydrogencarbonate ions) and leaves the red blood cell and enters blood plasma to be transportedCarbon dioxide enters alveoliHydrogencarbonate ions are converted back to carbonic acid then to water and carbon dioxide in red blood cells by carbonic anhydrase, thereafter diffusing out to plasma, then to alveoliExpirationCarbon dioxide is expelled when expiration occurs(d) describe the role of cilia, diaphragm, ribs and intercostal muscles in breathingPart of lungsInspirationExpirationDiaphragmContracts and flattensRelaxes and arches upwardsIntercostal musclesRelax internal, contract external (RICE)External relaxes, internal contracts (ERIC)RibsUpwards and outwardsDownwards and inwardsSternumUp and forwardMoves down back to original positionAir pressure to force air in or outDecreases in lungs, atmospheric pressure is higherIncreases in lungs, atmospheric pressure is lower(e) describe the effect of tobacco smoke and its major toxic components – nicotine, tar and carbon monoxide, on healthComponents of tobacco smokeCharacteristicsEffects on healthNicotineBlood clots more easilyIncreases risk of blood clots in blood vessels that might potentially obstruct flow of blood through themTarMay induce cancer in the epithelium that paralyses cillia lining air passagesAir sacs are blocked, reducing efficiency of gas exchange Dust particles trapped in mucus lining the airways cannot be removedCarbon monoxideDamages lining of blood vesselsIncreases risk of blood clots in blood vessels that might potentially obstruct flow of blood through themIncreases rate of fat deposition on inner arterial wallObstructions slow down blood flow, decreasing efficiency of rate of oxygen distribution and carbon dioxide removal, slowing glucose productionCombines more readily than oxygen to form carboxyhaemoglobinReduces oxygen transport efficiency of red blood cells as oxygen has to compete with carbon monoxide to bind with haemoglobinEffects of tobacco smoke on healthExplanationChronic Bronchitis due to excessive irritant particles within smokeEpithelium lining the airways is inflamedExcessive mucus secreted by the epitheliumMucus lining airways cannot be removedPersistent coughing needed to clear airways and breathe, increasing the risk of lung infections and emphysemaSevere breathlessness as airways become blockedEmphysema due to persistent violent coughing of chronic brochitisSevere breathlessness as airways become blockedLungs are inflated with airLungs lose elasticityPartition walls between air sacs break in violent coughingSurface area for gaseous exchange decreasesMore severe breathlessness(f) define and state the equation, in words and symbols, for aerobic respiration in humansEquation for aerobic respirationOxidation of food substancesto release a large amount of energy (CO2 + H2O as waste)GlucoseOxygenCarbon dioxideWaterEnergy is releasedC6H12O66 O26 CO26 H2OLarge amount of energy(g) define and state the equation, in words only, for anaerobic respiration in humansEquation for anaerobic respirationBreakdown of food substances in the absence of oxygenLess energy released than aerobicGlucoseWith the absence of oxygenLactic acidLittle energy(h) describe the effect of lactic acid in muscles during exerciseAnaerobic respirationEffect of lactic acidDuring exerciseRight after exerciseWhen the intensity of exercise is raised, muscular contractions become more vigorousAerobic respiration is unable to meet the higher energy demand, so anaerobic respiration also occursThis causes lactic acid to build up slowly in muscles Glucose Lactic acid + Small amount of energyWhen lactic acid concentrations become high enough,the high acidity causes muscular pains and fatigue,increasing the need for the body to rest and recover through deep breathingOxygen debt is paid off through deep breathing Lactic acid is quickly oxidised to form carbon dioxide and waterLactic acid + Oxygen Carbon dioxide + WaterThe oxidation of some of the lactic acid provides energy for the conversion of the remaining lactic acid to glucoseUse the knowledge gained in this section in new situations or to solve related problems9. Excretion in HumansContent? Structure and Function of Kidneys? Kidney DialysisLearning Outcomes:Candidates should be able to:(a) define excretion and explain the importance of removing nitrogenous and other compounds from the bodyTermDefinitionImportanceExcretionProcess by which metabolic waste products and toxic materials are removed from the body of an organismMetabolic waste products and toxic materials can be poisonous and harmful if they accumulate in the bodyIf they cannot be converted to harmless substances, excretion is the only way to remove them (b) outline the function of kidney tubules with reference to ultra-filtration and selective reabsorption in the production of urineProcessesKidney portionsFunctionsUltra-filtrationRenal capsule leading to each tubuleGlucose, mineral salts, amino acids, water and nitrogenous waste products is ultrafiltrated from the glomerulous to the renal capsuleAfferent arteriole is wider than efferent arterioleCreates a high hydrostatic blood pressureBasement membrane covering the capillaries has small pores Allows only some substances to pass through by being partially permeableSelective reabsorp-tionProximal convoluted tubuleSome mineral salts, all glucose and all amino acids are reabsorbed into blood capillariesLoop of HenleSome water reabsorbed into blood capillariesDistal convoluted tubuleSome water and some salts reabsorbed into blood capillariesCollecting tubuleSome water reabsorbed into blood capillariesUrine collectionRenal pelvis, ureter, urinary bladder, urethraThe remaining solution of excess water, excess salt and nitrogenous waste products (e.g. urea, uric acid and creatinine) form urine and is stored in urinary bladderDiagram(c) outline the role of anti-diuretic hormone (ADH) in the regulation of osmotic concentrationStimulusReceptorEffectorsCorrective mechanismWater potential in blood plasma risesHypothalamus in the brain monitors and senses a rise in water potentialPituitary glandLess anti-diuretic hormone (ADH) released from the pituitary gland into the bloodstreamKidney tubules reabsorb less water into blood capillariesUrine turns more dilute and increases in volumeWater potential in blood plasma fallsHypothalamus in the brain monitors and senses a fall in water potentialPituitary glandMore anti-diuretic hormone (ADH) released from pituitary gland into bloodstreamKidney tubules reabsorb more water into blood capillariesUrine turns more concentrated and decreases in volume(d) outline the mechanism of dialysis in the case of kidney failureMechanismOutlineBlood is drawn from the artery in patient’s arm It is then pumped into a tubing with partially permeable walls bathed in a specially controlled dialysis machineEnsures that excretion is performed without much disturbance on the body’s homeostatic systemSmall molecules like urea and other metabolic waste products diffuse in the fluidBlood cells, platelets and big molecules remain in the tubingTakes the place of the failed kidney to enable excretion to continue taking placeThe filtered blood is then returned to a vein in the patient’s armEnsures that there is no change in rate of flow of blood between the artery and veinDiagrams1342390254000283019568707000AdaptationsFunctionsSame concentration of essential substances like mineral saltsEnsures that they do not diffuse out of the bloodstream, or that minerals can diffuse into the bloodsteam if it lacks mineralsLong, narrow and coiled Increases surface area to volume ratio to speed up exchangeDoes not contain any metabolic waste products, excess water and mineral saltsConcentration gradient allows these products to diffuse out of the tubing, and water potential of blood to be maintainedDirection of flow of dialysis fluid is opposite that of blood flowMaintains concentration gradient to remove waste productsUse the knowledge gained in this section in new situations or to solve related problems10. HomeostasisContent? Principles of Homeostasis? SkinLearning Outcomes:Candidates should be able to:(a) define homeostasis as the maintenance of a constant internal environmentTermDefinitionFull definitionHomeostasisThe maintanence of a constant internal environmentThe maintanence of a constant internal environmentthat occurs whenever a receptor detects a change in condition of the internal environment, stimulates a self-regulatory corrective mechanism to bring about the reverse effect of the stimulus, and receives a negative feedback when the condition is restored(b) explain the basic principles of homeostasis in terms of stimulus resulting from a change in the internal environment, a corrective mechanism and a negative feedbackPrinciplesExplanationStimulusA change in the internal environment that is from the normal condition requires homeostasis to maintain it and bring the condition back to normalReceptorOrgans or structures that can detect the stimulus to stimulate the effectorCorrective mechanismMechanism is stimulated to bring about the reverse effect of the stimulus, usually through regulatory fluids, to correct the condition until it is normal againNegative feedbackAfter a system has brought about an opposite effect to changes in the system,negative feedback is the process of restoring the system to its original state, undisturbed,through nerve impulses to the receptor(c) identify on a diagram of the skin: hairs, sweat glands, temperature receptors, blood vessels and fatty tissueDiagram of the skin2186811422910 temperature receptor00 temperature receptor28055-28072 (d) describe the maintenance of a constant body temperature in humans in terms of insulation and the role of: temperature receptors in the skin, sweating, shivering, blood vessels near the skin surface and the co-ordinating role of the hypothalamusMaintanencePartsFinal effectMechanismInsulationFatty adipose tissueSlows down heat productionFound beneath the dermis to store fatSlows the loss of heat through insulationTemperature sensingTemperature receptors and hypothalamus of the brainVia receptors and effectors of homeostasisSenses temperature changes from surroundingsSends nerve impulses to hypothalamus of the brain, which receives information to be activatedSends nerve impulses to target organsVentilationLungsSpeeds upheat lossMore carbon dioxide and water vapour is exhaled,causing heat to be lost through these gasesMetabolic rateCells in generalSpeeds upheat productionIncrease in metabolic rateSlows downheat productionDecrease in metabolic rateSweatingSweat glands, duct and poresSpeeds upheat lossSweat containing latent heat of vapourisationis produced by the sweat ductand released from the sweat pores will evaporate, thus removing heat ShiveringSkeletal musclesSpeeds upheat productionContracts spasmodically in a reflex action known as shivering to increase heat productionBlood vessels near the skin surfaceArterioles, capillaries and venulesSpeeds upheat lossArterioles vasodilate to allow more blood flow to capillaries,transferring more heat by conduction and radiation to the skin surface then atmosphere,bringing less heat back through the venulesShunt vesselsSpeeds upheat lossShunt vessels constrict to allow less blood to be brought back to body parts through the venulesand more blood to flow to capillaries,thus less heat is brought back to the body partsSlows downheat lossShunt vessels dilate to allow more blood to be brought back to body parts through the venulesand less blood to flow to capillaries, thus more heat is brought back to the body partsUse the knowledge gained in this section in new situations or to solve related problems11. Co-ordination and ResponseContent? Receptors – Eye? Nervous System – Neurones (Reflex Action)? Effectors – Endocrine GlandsLearning Outcomes:Candidates should be able to:(a) state the relationship between receptors, the central nervous system and the effectorsPartRelationship in responseReceptorsGathers information and converts it into electrical signals known as nerve impulsesCentral nervous systemNerve impulses are transmitted through nerves in the peripheral nervous system to the central nervous system of the brain and spinal cord to interpret the nerve impulses and is stimulated to take actionEffectorsImpulses are transmitted by nerve impulses to effectors to carry out intended actions(b) describe the gross structure of the eye as seen in front view and in horizontal sectionDiagram264398153975choroid00choroid93345320834cornea00cornea3001645155702000295846514503400030803851657350to brain00to brain28755171187837retinaoptic nerve00retinaoptic nerve15738382047277sclera00sclera29432251810224003048001607820lens00lens1213485826609suspensory ligaments00suspensory ligaments2052320844389ciliary body00ciliary body280606518478500010490207753350010604501166495001060450843915002907030680720fovea00fovea1060450110680500131445063881000396875107124500-196851337945pupil00pupil812165982980001524001071245 iris00 iris (c) state the principal functions of component parts of the eye in producing a focusedimage of near and distant objects on the retina#Eye part for imageryFunction1RetinaLight sensitive area2Blind spotInsensitive area over optic nerve3FoveaLight rays are sharply focused here4Optic nerveTransmits nerve impulses5ChoroidSupplies oxygen and nutrients to the eye via blood vessels in it#Eye part for accommodationFar visionNear vision6Ciliary muscles of ciliary bodyRelaxes and pulls the suspensory ligamentsContracts and relaxes pull on suspensory ligaments7Suspensory ligamentsBecomes taut and pulls the edge of lensSlackens and relaxes8LensPulled thinShrinks and thickens#Supporting eye partsFunction9ConjunctivaCovers the scleraSecretes mucus for a moist eyeball10ScleraShapes the eyeProtects the eye from mechanical injury11CorneaRefracts light into eye12Aqueous humorKeeps eyeball firmRefracts light into pupil13Iris Controls intensity of light that enters14PupilAllows entry of light15Vitreous humorKeeps eyeball firmRefracts light onto retina16Rectus muscleAllows the eyeball to move(d) describe the pupil reflex in response to bright and dim lightFocusReceptorsImpulsesLight rays from the [nature of object] object are sharply focused on retinaPhotoreceptors are stimulated and sends nerve impulses to the brainNerve impulses travel through the optic nerve to the brain for it to interpret the pulses and the person to see the objectEye partsDim lightBright lightAnswering instructionsCircular muscles of irisRelaxesContractsWrite what contracts first before writing what relaxesRadial muscles of irisContractsRelaxesPupilDilatesConstrictsThen write the final result: Ensures that the right amount of light enters the eyeAmount of light entering eyeHigherLower(e) state that the nervous system – brain, spinal cord and nerves, serves to co-ordinate and regulate bodily functionsPartsRoles in coordinating bodily functionsBrainConsists of cranial nerves in which impulses are received from the receptor, pain is felt, and an intended action is made, passing this information to the effector by neurones in a cranial reflexSpinal cordConsists of spinal nerves in which impulses are brought to the brain through relay neurones in a cranial reflex for an action to be undertaken, or are carried from sensory to motor neurone by grey matter in a spinal reflexNervesAllow impulses to be brought to the neurones in spinal cord and brain in a reflex action(f) outline the functions of sensory neurones, relay neurones and motor neuronesDiagram1703070-4919brain cell in grey matter of brain00brain cell in grey matter of brain2623185189230white matter of spinal cord00white matter of spinal cord2623185226695002705735168910002788285444500278828538354000121539028448000-4508553975dorsal root ganglion00dorsal root ganglion3927475687705synapses00synapses28295608610600027882851013460006794501611630006794509271000067945011823700018288001981200motor neurone00motor neurone194373520224750018288002187575001719580417195relay neurone00relay neurone-3810589280receptor00receptor234950284480skin00skin26650952343785grey matter of spinal cord00grey matter of spinal cord23096350721875752349339effector (muscle)00effector (muscle)270573510350500192611634925pin00pin-60960831215sensory neuronecell bodies00sensory neuronecell bodiesNeuronesFunctionsSensoryTransmits nerve impulses from the receptors to the central nervous systemRelayTransmits nerve impulses from the sensory neuroneto the motor neuroneto the brain in a cranial reflexMotorTransmits the central nervous system to the effectors to produce a response(g) discuss the function of the brain and spinal cord in producing a co-ordinated response as a result of a specific stimulus in a reflex actionStimulusReflexReceptorsSpinal cordEffectsTouching a hot objectCranial reflex (for upper body parts)Heat on objectstimulates thermo-receptors in skinNerve impulsesare transmitted by a sensory neurone to the grey matter of spinal cordand then cross a synapse to a relay neurone where they willbe transmitted to the brainPerson feels the sensation of paincross another synapse to a motor neurone, then to the biceps muscle effectorBiceps muscle contractsHand withdrawsTap on tendon below the knee capSpinal reflex (for lower body parts)Tap on knee tendonstimulates stretch receptorNerve impulses are transmitted by a sensory neurone to the grey matter of spinal cordand then cross a synapse to the motor neurone, then to the knee muscle effectorKnee muscle effector contractsLeg jerk forwards(h) define a hormone as a chemical substance, produced by a gland, carried by the blood, which alters the activity of one or more specific target organs and is then broken down by the liverOutlineDefinitionSubstanceChemical substance...Production...produced by an endocrine gland...Carrier...carried by the blood...Effect...alters the activity of one or more specific target organs...Destruction...and is then destroyed by the liver(i) explain what is meant by an endocrine gland, with reference to the islets of Langerhans in the pancreasMeaning of endocrine glandReference to islets of Langerhans in the pancreasDuctless glands of internal secretion that secretes hormones directly into the bloodstream...Islets of Langerhans are cells in the pancreas that secrete insulin and glucagon when blood glucose levels are above normal levels and when they are below normal levels respectively... to be distributed around the body through blood...These hormones are transported by blood until they reach body parts they require their effects... to alter the activity of one or more specific target organsInsulinStimulates liver and muscle cells to convert glucose into glycogen for storageGlucagonGlycogen, fats, amino acids and lactic acid into glucose(j) state the role of the hormone adrenaline in boosting blood glucose levels and give examples of situations in which this may occurRole of the hormone adrenaline in boosting blood glucose levelsExamples of situationsSpeeds up the breakdown of glycogen and glucose in liver and musclesIncreases metabolic rate, releasing more energy in respirationIncreases rate of heartbeat, resulting in rise in blood pressure, thus oxygen and glucose are carried faster to musclesConstricts arterioles in skin to cause paleness, resulting in more blood and hence more oxygen and glucose to be channeled to musclesFearAngerAnxietyStress(k) explain how the blood glucose concentration is regulated by insulin and glucagon as a homeostatic mechanismReceptor-effectorTargetEffectsFeedbackIslets of Langerhans of pancreas sense increase of glucose levels and secrete insulinLiver and musclesIncreases permeability of cell membranes to glucose (to increase the rate of glucose uptake by cells)Stimulates liver and glucose (to convert excess glucose to glycogen for storage)Increase oxidation of glucose during tissue respirationNegative feedback to the receptorIslets of Langerhans of pancreas sense decrease of glucose levels and secrete glucagonLiver and musclesStimulates the conversion of glycogen, lactic acid, fats and amino acids to glucoseNegative feedback to the receptor(l) describe the signs, such as an increased blood glucose level and glucose in urine, and the treatment of diabetes mellitus using insulinDiabetes mellitusSignsReasonsTreatmentPersistently high blood glucose levelsKidney tubules reabsorb the maximum amounts of glucose it is able to reabsorb and cannot be stored and utilised by tissue cellsDaily injection of insulin (supply sugary foods if too much insulin is used, there’s too much exercise or too little food, otherwise a coma may result)Constant, consistent regulation of exercisingMetformin tablets and insulin injectionsPresence of glucose in urineKidney tubules do not have sufficient time to reabsorb glucose during selective reabsorption, and hence excreted in urineHealing of wounds is slow and difficultAs there are no reserves of glycogen, the body is unable to assimilate glycogen and convert it to new protoplasm to heal woundsOxidises fats instead to produce energy and poisonous ketones that may cause further harmLoses weightReserves of glycogen are at minimal levelsUse the knowledge gained in this section in new situations or to solve related problemsTHEME III: CONTINUITY OF LIFEOverviewThe many aspects of form and function that we have examined in this syllabus can be viewed in the widest context as various adaptations aimed at ensuring reproductive success. Reproduction is vital for the survival of species across generations. In 1953, James Watson and Francis Crick developed the model for deoxyribonucleic acid (DNA), a chemical that had then recently been deduced to be the physical carrier of inheritance. In this section, we examine how genes interact to produce hereditary characteristics in the offspring. This section focuses on understanding the processes involved in the continuity of life and how genetic information is passed from one generation to the next.Extracted from BIOLOGY GCE ORDINARY LEVEL (2014) Syllabus Document12. ReproductionContent? Asexual Reproduction? Sexual Reproduction in Plants? Sexual Reproduction in Humans? Sexually Transmitted DiseasesLearning Outcomes:Candidates should be able to:(a) define asexual reproduction as the process resulting in the production of genetically identical offspring from one parentTermDefinitionIn other wordsAsexual reproductionThe process resulting in the production of genetically identical offspring from one parent with no fusion of gametesMitosis (2n to 2n×2)(b) define sexual reproduction as the process involving the fusion of nuclei to form a zygote and the production of genetically dissimilar offspringTermDefinitionIn other wordsSexual reproductionThe process resulting in the production of a zygote and genetically dissimilar offspring, involving the fusion of nuclei1. Meiosis (2n to n×4)2. Fertilisation (n×2 to 2n)(c) identify and draw, using a hand lens if necessary, the sepals, petals, stamens and carpels of one, locally available, named, insect-pollinated, dicotyledonous flower, and examine the pollen grains under a microscopeTypical diagram of a flowerDiagram of insect-pollinated Clitoria(d) state the functions of the sepals, petals, anthers and carpelsPartFunctionsSepalEncloses and protects the other parts of the flower in the bud stagePetalAttracts insects for pollination, brightly colouredProvides a platform for insects to land on for insect pollinationStamenAntherProduces pollen grains and splits open to release them when matureFilamentHolds the anther uprightCarpelStigmaReceives pollen grains from the anther from the surroundingsSecretes sugary fluid to stimulate pollen grains to germinateStyleConnects the stigma to the ovary for the male gamete to travel and meet the female gameteHolds stigma in suitable position to trap pollen grainsOvaryEncloses one or more ovules containing an ovum(e) use a hand lens to identify and describe the stamens and stigmas of one, locally available, named, wind-pollinated flower, and examine the pollen grains under a microscopeTypical diagram of a flowerDiagram of wind-pollinated Ischaemum muticum(f) outline the process of pollination and distinguish between self-pollination and cross-pollinationTermDefinitionInsect pollinationWind pollinationPollinationTransfer of pollen grains from the anther of a flower to the stigma of the same or different flower of the same speciesThe heavy insect lands on standard petalFollows the nectar guide into flowerSqueezes past anther to reach nectarCollects pollen on its body while enteringPollen is dusted onto stigma of the same flower by insect when it leaves, or another flower of the same species (when it enters that other flower to collect nectar again)Pendolous filaments hang out of the bracts to expose mature anthers to the windDust-like pollen is shaken free upon swaying of filament in windHigh surface area feathery stigmas that project out then receives the pollen floating in the windDifferencesSelf-pollinationCross-pollinationDefinitionPollen transferred to stigma of same flower or different flower in same plantPollen transferred to stigma of a flower in another plant of the same speciesParent plantOnly one is requiredTwo is requiredProbabilty and locationStigma situated directly below the anthersMore likely to occurStigma situated some distance away from anthersLess likely to occurExternal factorsIndependent from external factorsDependent on external factorsWastageLess pollen and energy is wastedMore pollen and energy is wastedQualitiesBeneficial qualities are more likely to be passed down to the offspringBeneficial qualities may be inherited from both parentsVariationOffspring’s genes are similar to parent’sLess varietiesLower adaptabilityGreater genetic variationMore varieties producedHigher chance of surviving changes in environment SurvivalOffspring may be weaker, smaller and less resistant to diseasesViable seeds which are capable of surviving longer before germination are produced(g) compare, using fresh specimens, an insect-pollinated and a wind-pollinated flowerDifferencesBy insectsReasonBy windReasonNectarPresent Food to attract insectsAbsent To prevent insect pollinationNectar guidesPresent Guide the insects towards the nectarAbsent To prevent insect pollinationPetalsPresent Large, brightly colouredAbsent Flowers are small, dull colouredPollenFairly abundant, large, rough, usually hairyTo cling onto insect bodies easilyMore abundant, smooth, tiny and light More easily blown about by windStigmaSmall and compact To prevent wind pollinationLarge and feathery, protrudes out Large surface area to trap pollenStamenNon-pendulous To prevent wind pollinationPendulous filaments, long protruding anthers Easily shaken out from anthersScentFragrant or sweet-smellingAttracts insectsNo scentTo prevent insect pollination(h) describe the growth of the pollen tube and its entry into the ovule followed by fertilisation (Production of endosperm and details of development are not required)#AcroynmStagesDescription1SSugary fluidMature stigma secretes sugary fluidPollen grains germinatePollen tube grows out from each grain2EEnzymesPollen tube secretes enzymesSurrounding tissues of stigma and style are digestedTube penetrates through the style3MMicropylePollen tube enters the micropyleGenerative nucleus divides, forms two male gametesPollen tube nucleus disintegrates4FFertilisationTip of pollen tube absorbs sapBursts to release male gametesOne male gamete fuses with ovum to form zygote5EEmbryoZygote dividesDevelops into embryo formed in the seed(i) identify on diagrams of the male reproductive system and give the functions of: testes, scrotum, sperm ducts, prostate gland, urethra and penisDiagrams of male reproductive system#PartFunctions1TestisProduces sperms and male sex hormones like testosterone2ScrotumContains testes lying outside main body cavityProvides sperms with a suitable temperature (slightly lower than body temperature) for proper development3Sperm ductConducts sperms from the testis to seminal vesicle to be stored temporarily before being released to urethra4Prostate glandSecretes a slippery alkaline fluid with Cowper’s gland and seminal vesicle It contains nutrients and enzymes to nourish sperms and allow sperm motility5UrethraConducts urine and semen out of the body separately, with sphincter muscle to prevent urine from coming out during ejaculation6PenisDeposits semen into the female reproductive system through the vagina after blood fills the erectile tissue, turning it erect(j) identify on diagrams of the female reproductive system and give the functions of: ovaries, oviducts, uterus, cervix and vaginaDiagrams of female reproductive system#PartFunctions1OvaryProduces ova and releases them when matureProduces female sex hormones2OviductConducts mature egg from the ovary into the uterus through funnel-like openingLocation from egg fertilisation3UterusProvides a suitable environment for foetal development during pregnancyContains smooth muscles in the uterine wall which contract to expel the foetus during birth4CervixKeeps the opening of the uterus closed to maintain pregnancyDilates during birth to allow the foetus to pass out of the uterus during birth5VaginaAllows flow of blood out of the uterus during menstruationReceives semen during sexual intercourseAllows passage of foetus out of the uterus during birth(k) briefly describe the menstrual cycle with reference to the alternation of menstruation and ovulation, the natural variation in its length, and the fertile and infertile phases of the cycle with reference to the effects of progesterone and estrogen only#Stages of menstrual cycleDescription of stageDurationNature of cycle1MenstruationUterine lining breaks down and flows from the uterus out of the body by menstrual flow through the vaginaDays 1 to 5Alternates between menstruation and ovulation2Repair and growth of uterine liningOvaries secrete oestrogen to ensure that the uterine is vascularised, thickened and well supplied with blood vesselsDays 6 to 133OvulationOva are produced during the fertile period Day 144Ovulation inhibitedProgesterone and oestrogen maintain the thickness of uterine lining and further supply blood vessels with blood capillariesDays 15 to 28Outcome of fertilisationEggHormonesUterine liningRole of placentaNot successfulEgg breaks down Progesterone is not secretedUterine lining breaks downCycle repeatsNot applicableSuccessfulZygote develops into embryoSecretion of progesterone and oestrogen sustained by ovary and then placenta later onEmbryo embeds itself in uterine liningPlacenta develops from the embryonic villi (embedded in uterine lining)Secretion of hormones by the ovary stops after placenta is able to start secreting themAspect of cycleAverageRangeRemarksNatural variation in its length28 daysAnomalies of 21 to 33 daysMay take up to 3 years for periods to be regularStress, tiredness, illnesses, and an unbalanced diet or malnutrition, may alter or stop the menstrual cycleAspect of cycleGameteLifespanHigh presence in uterusConditions requiredFertile and infertile phases of the cycleSperms2 to 3 daysEjaculation starts on day 11Uterine lining must have been repaired by thenOva1 to 2 daysDays 14 to 16Ovulation must have occurred on day 14(l) describe fertilisation and early development of the zygote simply in terms of the formation of a ball of cells which becomes implanted in the wall of the uterus#AcronymStagesDescription1PPenetrationAcrosome of sperm releases enzymesPart of the egg membranes are broken down2FFertilisationOne sperm nucleus entersNucleus fuses with egg to form a diploid zygoteOther sperms eventually die3IImplantationCilia and peristaltic movements sweep zygote along oviductZygote divides by mitosis to form a ball of cellsEmbryo reaches uterus after 5 days from fertilisationEmbeds in uterine lining after 2 days4PPlacentaVilli with blood capillaries grow from embryo to uterinePlacenta forms after villi grows fullyEmbryo separates from placentaUmbilical cord connects the embryo to placenta5FFetus developsAll major organs are formed, 10 to 12 weeks after fertilisation(m) state the functions of the amniotic sac and the amniotic fluidPartsFunctionsAmniotic sacEncloses the fetus in the amniotic cavity containing amniotic fluidAmniotic fluidCushionsSupports and cushions fetus before birthShockAbsorbs shock if mother fallsInjuryProtects fetus against physical injury due to its incompressibilityLubricationLubricates and reduces friction in the vagina or birth canal MovementAllows fetus to move freely during growth(n) describe the function of the placenta and umbilical cord in relation to exchange of dissolved nutrients, gases and excretory products (Structural details are not required)PartsFunctionsPlacentaOxygen and dissolved substancesAllows oxygen and dissolved substances to diffuse from the mother's blood into the fetus’ bloodExcretory productsAllows excretory products such as urea and carbon dioxide to diffuse from the fetus’ blood to mother’s bloodAntibodiesAllows protective antibodies to diffuse from the mother’s blood into the fetus' blood which protect the fetus against certain diseasesProgesteroneProduces progesterone which maintains the uterine lning in a healthy state during pregnancyUmbilical cordCarbon dioxide and metabolic waste products by arteriesTransport deoxygenated blood and metabolic waste products from the fetus to the placenta through 2 umbilical arteriesOxygen and food substances by veinsTransport oxygenated blood and food substances from the placenta to the fetus through 1 umbilical vein(o) discuss the spread of human immunodeficiency virus (HIV) and methods by which it may be controlledMeans of spread of HIVMethods of its controlIn generalSexSexual intercourse with an infected personNo sexKeep to one sex partner or do not have sexTransmission can only be through bodily fluids and when infected blood contaminates the new victim's bloodTransmission will not occur by surface level contact or flow as it does not enter the skinCondomDuring sex, males should wear a condom to protect themself in case their partner has HIVHypodermic needlesSharing of hypodermic needles, if not sterilised properly, like acupuncture and ear piercingDrug abuseDo not abuse drugs, as drug addicts usually share needles and chances of getting HIV is higherDisposeUse sterilised or disposable needles alwaysBlood transfusionBlood transfusion from an infected personContaminationDo not share instruments that can break the skin and may be contaminated with bloodPregnancyInfected mothers may transfer the virus to fetus through umbilical cordN.A.N.A.Use the knowledge gained in this section in new situations or to solve related problems13. Cell DivisionContent? Mitosis? MeiosisLearning Outcomes:Candidates should be able to:(a) state the importance of mitosis in growth, repair and asexual reproduction#ImportanceDescription of importance of mitosisExamples1GrowthMitosis allows for the growth and development of a multicellular organismDevelopment of a fertilised egg into an adult human being2RepairMitosis allows for the repair or replacement of worn-out parts of the bodySealing up of wounds from injuriesReplacement of dead and worn-out cheek cells may be shed during teeth brushing and mouth rinsing3Asexual reproductionMitosis is also the basis for asexual reproductionEnable shoots and roots to develop in storage organs (e.g. bulbs)(b) explain the need for the production of genetically identical cells and fine control of replication#Reasons for production of genetically identical cellsDescription of reasons1GrowthMitosis allows for the growth and development of a multicellular organism2RepairMitosis allows for the repair or replacement of worn-out parts of the body3Asexual reproductionMitosis is also the basis for asexual reproduction#Reasons for fine control of DNA replicationRelated mechanism in control of DNA replication 1Ensures that cells produced are genetically identicalChromosomes of parent nucleus are already duplicated before mitosis begins2Ensures that 2 sets of identical genetic material is present before cell divisionArrangement of chromosomes at the equator during metaphase ensures that chromosomes are shared equally between the 2 daughter cells3Prevents abnormal development of the embryoIf there are errors in DNA replication, they will be transmitted to the daughter cellsMay lead to harmful changes to genes and affect how the cells functionEmbryo may not develop normally4Prevents cancerIf there are errors in DNA replication, this may cause cells to lose the ability to control the way they divide and their normal functions(c) identify, with the aid of diagrams, the main stages of mitosis (e) identify, with the aid of diagrams, the main stages of meiosis#StageMitosisMeiosis IMeiosis II1IInterphase2PProphase861060569595nuclear envelope00nuclear envelope873125405130centromere00centromere877570107950microtubules(spindle fibres)00microtubules(spindle fibres)789416253365a pair ofhomologouschromosomes00a pair ofhomologouschromosomes661035-25400centriole00centriole 3MMetaphase1221105405765pole00pole1122680-22860equator00equator-2921075501500 4AAnaphase106807010795separated chromosome00separated chromosome251460499745251460383540002590804152900076644573660000784860-2794000-38100-4254500760730-4318000-43815-45085005TTelophase1062355361950004508535369500222253314700035560361315001045210299720001060450334645001049020365760003175029781500508002813050043180395605001228090410845 nuclear membrane reforms00 nuclear membrane reforms117729019050chromosome uncoiling00chromosome uncoiling144018029337000196215-10795nuclear membranes00nuclear membranes1064895451485nuclear membranes00nuclear membranes-47625-4508500-33020-2603500 6CCytokinesisDifferencesMitosisMeiosis DefinitionCell division by which one single diploid parent result in the production of two daughter cellsCell division by which one single parent diploid cell divides to produce four haploid cellsDaughter cellsAll are identical the original parent cellGametes with half the diploid chromosomes in parent and may contain variations from parent cellPairingPairing of homologous chromosomes do not occurHomologous chromosomes pair up at Prophase I Crossing overDoes not occurMay occurDivisionsOne nuclear divisionTwo nuclear divisions for a reduction division(d) state what is meant by homologous pairs of chromosomesTermMeaningPropertiesSimilaritiesDifferencesHomologous pairs of chromosomesTwo chromosomes that pair along their whole length during synapsisSame shape, genes and length with genes found on the same lociAlleles of each trait may not be the same(f) define the terms haploid and diploid, and explain the need for a reduction division process prior to fertilisation in sexual reproductionTermDefinitionDiploidThe number of chromosomes present in a normal body cell of a species of an organismHaploidThe number of chromosomes present in a gamete of a species of organism, containing half the number of chromosomes as the normal body cellReduction divisionThe process by which one diploid parent nucleus divides to form four haploid daughter nuclei, where each daughter nucleus contains half the number of chromosomes as the original nucleus in the parent cell(This is because of the separation of homologous chromosomes during Anaphase I)FertilisationThe process by which gametes fuse to produce a zygote which restores the diploid number of chromosomesNeed for reduction divison prior to fertilisationA reduction division prevents doubling of the number of chromosomes in each successive generationThe number of chromosomes after each successive generation will thus remain diploid(g) state how meiosis and fertilisation can lead to variationProcessesExplanationMeiosisCrossing overTwo non-sister chromatids of homologous chromosomes may cross and twist around each other at a chiasmaCoiling causes exchange of chromatids or crossing overNew combinations of genes along chromosome are producedIndependent assortmentFour chromosomes randomly pair up with one other Two assorted pairs of chromosomes form, each in every pair face opposite poles of the cellNew combinations of genes are produced after meiosis IFertilisationFertilisation involves the fusion of a male gamete and female gameteThese gametes have been produced by meiosis which crossing over may have occurredAs new combinations of genes are produced, the new organism may vary from parentsUse the knowledge gained in this section in new situations or to solve related problems14. Molecular GeneticsContent? The Structure of DNA? The Role of DNA in Protein Synthesis? Genes? Genetic Engineering and Medical BiotechnologyLearning Outcomes:Candidates should be able to:(a) outline the relationship between DNA, genes and chromosomesStructureDescriptionDiagramGeneA gene is a sequence of nucleotides containing genetic information used to make proteinsDNADNA (deoxyribonucleic acid) consists of two parallel strands of nucleotides twisted around each other in a double helixEach strand of DNA is made up of many genes ChromosomeA chromosome is made of condensed chromatin threads, which consists of DNA wrapped with proteins(b) state the structure of DNA in terms of the bases, sugar and phosphate groups found in each of their nucleotidesComponents of a nucleotideDescriptionPolynucleotide formationNitrogenous baseAdenine or Cytosine or Guanine or Thymine Nucleotides can be joined together to form polynucleotidesDeoxyribose sugarForm the sugar-phosphate backbone in a polynucleotidePhosphate groupDiagramsNucleotidePolynucleotide (section)(c) state the rule of complementary base pairingRuleDescription of the rule to form pairs of basesTA ruleThymine always hydrogen bonds with adenine to form complementary basesCG ruleCytosine always hydrogen bonds with guanine to form complementary bases(d) state that DNA is used to carry the genetic code, which is used to synthesise specific polypeptides (details of transcription and translation are not required) Molecules involved in protein synthesisRoleDNADNA carries a gene that occupies a locus along a chromosomeGeneA gene carries a genetic code that is used to synthesise specific polypeptides It controls exactly how a particular protein is made in the cell through transcription and translationRNARNA (ribonucleic acid) is a temporary molecule to transfer information from DNA to molecules directly involved in protein synthesisIt contains uracil instead of thymine, which also bonds with adenine only(e) state that each gene is a sequence of nucleotides, as part of a DNA moleculeTermDescriptionGeneEach gene is a sequence of nucleotides as part of a DNA moleculeThe sequence of nucleotides stores a message that determines how a protein should be made(f) explain that genes may be transferred between cells. Reference should be made to the transfer of genes between organisms of the same or different species – transgenic plants or animalsTermDefinitonMethodGenetic engineeringTechnique used to transfer genes from one organism to anotherGenes are extracted (‘cut off’) from the cells of one organism and inserted into the cells of another organismExamples of transferBetween different speciesBetween same speciesGene transferredSoil fungus Myrothecium verrucariaHealthy geneDesired function of geneTo produce cyanamide hydratase enzyme that converts cyanamide to urea, a harmless source of nitrogenTo replace genes of lung disease cystic fibrosis when excessive mucus produced blocks the respiratory system, causing breathlessnessProductThis process produces transgenic plants since it is between different speciesThis process of gene therapy does not produce transgenic animals since it is between the same species(g) briefly explain how a gene that controls the production of human insulin can be inserted into bacterial DNA to produce human insulin in medical biotechnology#StepsProceduresKey molecules1Isolate the desirable human geneRestriction enzyme cuts out the gene for producing human insulin at 2 specific points from the insulin DNA, forming a single strand sequence of bases on each side of the geneRestriction enzyme2Plasmid preparationSame restriction enzyme cuts open the plasmid DNA (vector from a bacterial cell), forming a single strand sequence of bases complementary to bases on the sides of insulin DNARestriction enzyme3Join desirable gene to the plasmidDNA ligase joins the cut ends of the plasmid DNA and insulin DNA by complementary base pairing of both ends to form the plasmid containing the human insulin geneDNA ligase4Insertion of gene into E.coli bacteriaMix the plasmid with E.coli bacteria and heat shock is carried out temporarilyElectric shock5Plasmid multiplicationTransgenic bacteria makes copies of the plasmid when they reproduce when dividingDivision(h) discuss the social and ethical implications of genetic engineering, with reference to a named examplePrior knowledge of named exampleExampleBt corn (a plant)SynthesisBt gene from Bacillus thuringiensis bacteria is inserted into cornSignificanceBt gene produces a protein that is lethal to pests of the corn, but not lethal to humans and other vetebratesThis reduces agricultural loss due to pests attacksKnowledge required to respond to questionSocialimplications Threatens the safety of the environmentGenetically modified crops may be carried by wind to other places and grow quickly, potentially establishing themselves as weedsPollen grains from these plants may also fertilise wild relatives to form superweeds and compete with the natural speciesEthicalimplicationsMaking a staple crop more resistant under marginal conditions may be a potential boon for Third World agriculture as richer countries benefit at the expense of poorer countriesWorld food production may also be dominated by a small number of large companies with the technical know-how in the long run, leading to rising income inequalityUse the knowledge gained in this section in new situations or to solve related problems15. InheritanceContent? The Passage of Information from Parent to Offspring? The Nature of Genes and Alleles, and their Role in Determining the Phenotype? Monohybrid Crosses? Variation? Natural and Artificial SelectionLearning Outcomes:Candidates should be able to:(a) define a gene as a unit of inheritance and distinguish clearly between the terms gene and alleleTermsDefinitionsExamplesGene[Inheritance, for this chapter]A unit of inheritance and a section of a DNA that codes a particular trait[Molecular Genetics]A sequence of nucleotides as part of a DNA moleculeHeight of pea plantsColour of flowersAlleleAlternative forms of the same geneTall/short, Purple/white(b) explain the terms dominant, recessive, codominant, homozygous, heterozygous, phenotype and genotypeTermsDefinitionsExamplesPhenotypeVisible characteristics of an organismBlack fur on rabbits is a phenotype represented by BB and Bb genotypesGenotypeGenetic makeup of an organism to determine phenotypeBB, Bb, bb are genotypes that determine the phenotype of either black fur or white furHomozygousTwo copies of an allele controlling an organism’s trait are similarBB (Homozygous dominant)bb (Homozygous recessive)HeterozygousTwo alleles controlling an organism’s trait are differentBb (Heterozygous)DominantAllele which gives same phenotype in both homozygous and heterozygous conditionsB is the dominant allele (capital letter)BB and Bb represent the same phenotype RecessiveAllele which expresses itself only in the homozygous condition and does not express itself in the heterozygous condition b is the recessive allele (small letter)bb shows a different phenotype from BB and Bb CodominanceCondition in which both alleles exert equal effects in the offspring’s traitWhen IA is codominant to IB, Blood Group AB is the phenotypeIf RR shows red and rr shows white, then Rr represents pink(c) predict the results of simple crosses with expected ratios of 3:1 and 1:1, using the terms homozygous, heterozygous, F1 generation and F2 generationPunnettsquare(gametes bolded)BBBBBBBBBBBBBbBBBBbBBBBbBbBBBBbbBbbbBbbBbbbbBbbbbbbbbbbbbbbbOffspringphenotypic ratio111:1 (if codominant)1:31:2:1 (if codominant)1:11F1 and F2 generationThe F1 generation of 2 parents are the offsprings of the parentsThe F2 generation of 2 parents are the offsprings of the F1 generation above (d) explain why observed ratios often differ from expected ratios, especially when there are small numbers of progenyExplanation to learning outcomeObserved ratios often differ from expected ratiosas expected ratios are based mainly on chance and probabilityThis is especially when there are small numbers of progeny (offspring)when the actual number of progeny would be more unlikely to match the expected number preciselyas chances of the offspring to match its expected characteristic is lower than expected(e) use genetic diagrams to solve problems involving monohybrid inheritance. (Genetic diagrams involving autosomal linkage or epistasis are not required)Example of genetic diagram (must be based on question asked)OrganismPink flowerPink flowerParental PhenotypePink colourXPink colourParental GentoypeAaXAaGametes(must be circled)2621915-26035a00a2160524-25400A00A778510-31115a00a314325-31750A00AOffspring Genotype(from punnett square)AAAaAaaaOffspring PhenotypePurple colourPink colourPink colourWhite colour(f) explain co-dominance and multiple alleles with reference to the inheritance of the ABO blood group phenotypes – A, B, AB, O, gene alleles IA, IB and IOPhenotypeGenotypeAllele relationshipExam responseBlood Group AIAIA or IAIOIA dominant over IOExplain all sides, e.g. if asked to determine that an allele is dominant,explain why being dominant would cause the result andwhy the result will be different if the allele is recessiveBlood Group BIBIB or IBIOIB dominant over IOBlood Group ABIAIBIA is codominant to IBBlood Group OIOIONil(g) describe the determination of sex in humans – XX and XY chromosomesChromosome number in humansEach cell in humans has 23 pairs of chromosomesIt consists of 22 pairs of autosomes and 1 pair of sex chromosomes PhenotypeGenotype (in sex chromosomes)Allele relationshipMaleXYY dominant over XFemaleXX(h) describe mutation as a change in the structure of a gene, such as in sickle cell anaemia, or in the chromosome number, such as the 47 chromosomes in the condition known as Down syndromeMutationExample of Gene mutationExample of Chromosome mutationExampleSickle cell anaemiaDown SyndromeDetailsInherited diseaseHappens by chanceHow it happensSomeone with sickle cell anaemia produceshaemoglobin S instead of haemoglobin AIt is a homozygous recessive disease, aaMutation causes one gamete from either the male or female to have 2 copies of chromosome 21When it fuses with the normal gamete of the other sex, the zygote will have 3 copies of chromosome 21, resulting in 47 chromosomes instead of the normal 46EffectsStiff and sticky to form clumps in blood vessels which may obstruct blood flowLead to serious infectionsOrgan damageLow resistance to diseaseMental retardationStunted growthSpecial casesHeterozygous humans, Aa, without the disease:May pass on to the next generationCan survive better in a malaria prone areaOlder mothers have a higher chance of giving birth to a child with the disease than younger ones(i) name radiation and chemicals as factors which may increase the rate of mutationMutation catalystsExamplesRadiationUV light, Gamma radiationChemicalsMustard gas, Formadehyde, Ferrous and manganous salts(j) describe the difference between continuous and discontinuous variation and give examples of eachTermDefinitionVariationDifferences in traits between individuals of the same speciesDifferencesContinuous variationDiscontinuous variationIntermediate characteristicsYesNoDistinct phenotypeNoYes (to the extremes)Causes of variationGenesYesYesEnvironmentYesNoNumber of genesControlled by a few genesControlled by a single gene usuallyAdditive effect of genesYesNo(k) state that competition which arises from variation leads to differential survival of, and reproduction by, those organisms best fitted to the environmentTermMechanismNatural selectionVariation in a population means that some organisms are more well fitted to the environment,which may result in competitionThis leads to those organisms best fitted to the environment to survive better (i.e. differential survival)which allows more of these organisms to reproduce than those less fitted (i.e. differential reproduction)(l) give examples of environmental factors that act as forces of natural selectionExplanationPredation exampleDroughts exampleOrganismRabbitsFinchesSituationMutation took place and produced varieties of traits like coat colour and size of rabbit varietyThere was a natural variation in the sizes of the beaks of the finches on the Galápagos islandPlants on the island produce either big, hard and dry seeds from trees or small, soft and moist seeds from vines and creepersChange in environmentWhen a predator species start to thrive, rabbits of different varieties start move away from their dangerous habitat at risk of predation in search of other suitable habitatsWhen a drought occured for a period of a few years, many vines died due to lack of moisture and supply of small and moist seeds decreased sharply, causing relatively more seeds from trees to be available Type(s) at selective advantageType with light colour of fur coat and is bigger sized moved to an open plain and to escape predationFinches with bigger beaks survived the drought better as they were able to crack the harder seeds better and therefore better able to source for foodAppearanceAdaptationLight colourCamouflages wellLong hind legsEscape from predatorsLong earsDetect predatorsUpright positionSee further to source foodType with dark fur colour and is smaller sized moved to a dense forest and to escape predationAppearanceAdaptationDark colourCamouflages wellSmall size and able to crouchLess detectable as they are able to hide among logsType(s) at disadvantageThe type of rabbit with an appearance that makes it easy to spot by predators or rabbits that travel to a habitat that does not favour escape from predationFinches with smaller, weaker beaks died off during the drought as supply of soft seeds dropped sharply, food was not readily availableOne-sided survivalLight coated, bigger sized rabbits in open plains and dark coated, smaller sized rabbits in dense forests had the selective advantage and more of them survived predation to adulthoodFinches with bigger beak size had the selective advantage and more of them survived to adulthoodTime passesThese rabbits reproduced and started to have offsprings at a faster rate than other speciesThese finches reproduced and started to have offspring at a collectively faster rate than other speciesDominationThe big light coated rabbits and small dark coated rabbits dominated the population of their repective habitats in the next generationFinches with bigger beaks dominated the population in the next generation(m) explain the role of natural selection as a possible mechanism for evolutionTermDefinitionLink to evolutionNatural selectionMechanism that brings about adaptation to the environment and evolutionDifferent variants are selected for or against by different environment factors that act as selective pressuresOrganisms with favourable traits that are genetically determined will survive better and reproduceOffspring will inherit their traits over time, increasing the frequency of alleles for favourable traits and decreasing the frequency of alleles for non-favourable traits(n) give examples of artificial selection such as in the production of economically important plants and animalsProductionProcedureImproving plants by hybridisationTo cultivate a variety of wheat that has two main desirable traits, two parents each with one of the two traits is crossedSome new hybrids will have preferred combination of genes from both parents (desirable traits)The hybrid is propagated by vegatative means to prevent any repeats of hybridisation for the next generations as offspring is not identicalImproving animals by inbreedingSimilar process of hydrisation as above for new breeds of animals (e.g. cattle)Mating carried out instead of crossingInbreeding maintains the improved breed by breeding among closely related individualsDifferencesNatural selectionArtificial selectionDefinitionNature selects for organisms with favourable genes and traits that help them survive unique habitatsProduced by selective breeding by humansVarietiesProduced by mutationsOccurenceWhen natural environment conditions changeWhen humans select organism varieties to suit their needs, producing more diversityImportancePossible mechanism for evolution, which is the process by which present forms of living organisms have arisen from simpler ancestral formsUse the knowledge gained in this section in new situations or to solve related problemsTHEME IV: MAN AND HIS ENVIRONMENTOverviewAll living organisms are part of a complex network of interactions called the web of life. This sectionfocuses on the interrelationships among living things. These include two major processes. The first is the cycling of nutrients, as illustrated by the carbon cycle. The second major process is the flow of energy from sunlight to organisms further down the food chain.Human activities can upset natural ecosystems, causing permanent damage not just to localenvironments but also the global environment. As a part of this environment, humans must show asense of responsibility for its maintenance.Extracted from BIOLOGY GCE ORDINARY LEVEL (2014) Syllabus Document16. Organisms and their EnvironmentContent? Energy Flow? Food Chains and Webs? Carbon Cycle? Effects of Man on the Ecosystem? Environmental Biotechnology? ConservationLearning Outcomes:Candidates should be able to:(a) briefly describe the non-cyclical nature of energy flowNon-cylicalHeat energySupplyRespirationExcretion, egestionLight energyEnergy does not flow in a cycleHeat energy cannot be recycled nor used to do workEnergy needs to be constantly supplied to the ecosystemCarbon dioxide is produced for photosynthesisCarbon dioxide is produced when these waste products are decomposedCombines with chlorophyll to release chemical energy(b) explain the terms producer, consumer and trophic level in the context of food chains and food websTermExplanationProducerOrganisms that convert energy from the Sun into chemical energy and store it as food during photosynthesisConsumerOrganisms that obtain energy by feeding on other organismsTrophic levelStage of a food chain (e.g. producers are always located at the first trophic level)(c) explain how energy losses occur along food chains, and discuss the efficiency of energy transfer between trophic levelsHow energy is lostAmount of energy lostEfficiency of energy transferUneaten body partsFaeces as waste productsExcretory products, undigested matter egestedHeat loss during respirationWe usually assume 90% of energy is lost when energy is transferred to the next trophic level10% is passed downShort food chains are more efficient in energy transferLess energy is lost to the environment along the food chainMore energy is available to the final consumer(d) describe and interpret pyramids of numbers and biomassTermExplanationPyramid of numbersTo compare the number of organisms present in each trophic level at a particular time Pyramid of biomassTo compare the mass of organisms present in each trophic level at a particular timePyramid of numbersPyramid of biomassIf organisms at the topIf organisms at the bottomOrganisms at the bottom are greater in numbersare smaller in numbersare always smaller in numberscompared to those in the previous trophic levelcompared to those in the next trophic levelcompared to those in the next trophic levelthey are likely parasitic they are likely to be a producerThey also have higher rates of reproductionand hence small in sizethat is large in size (e.g. a tree)DiagramsPyramid of numbersPyramid of biomass-5673210737310-433471092517(e) describe how carbon is cycled within an ecosystemRemoval of carbon dioxideRelease of carbon dioxidePhotosynthesisPlants absorb CO2 from air to manufacture carbohydratesRespirationWhen organisms respire, C compounds are broken down and carbon dioxide is released to the environment as a by-productCarbon compoundsGlucose is converted to other C compounds like fats, amino acids and proteinsDecayThe bodies of dead organisms decay and are broken down into simple substances by decomposersAnimalsAnimals feed on plants and C compounds enter their bodiesFossil fuelsWhen organisms die, C compounds can be preserved in fossil fuels as coal, natural gas and oilCombustionWhen fossil fuels undergo combustion, C compounds preserved are broken down and carbon dioxide is released to the environmentDiagram of carbon cycleInferencesEnergy flow is non-cyclicalCarbon flow is cyclical(f) evaluate the effects of: ? water pollution by sewage and by inorganic waste ? pollution due to insecticides including bioaccumulation up food chains and impact on top carnivoresPollution formDescriptionEffectsResultInsectidesPoisonous chemicals used to kill insectsBioaccumulation Some insecticides (e.g. DDT) are insoluble in water, cannot be excreted and cannot be broken down, therefore have to be stored in fatty tissues of organismsThey accumulate in bodies of living organisms and pass along food chains, causing the consumers at the end of the food chain to contain high levels of insectidesBioamplification (final impact on top carnivores)These insectides end up in high concentrations in the bodies of the carnivores on the top of the food chain, and as they are in large amounts, they are poisonous and harmful to these organismsSewageWaste matter from homes or industriesEpidemicUntreated sewage may cause bacteria to enter drinking water and affect humans with diseases like choleraEutrophicationPhosphate and nitrate nutrients promote growth of algae and water plants, blocking out sunlight for submerged ones and they die by lack of food from photosynthesis (elaborate in terms of plant nutrition)Death of fishPhosphate and nitrate nutrients promote growth of bacteriaBacteria use more oxygen, so competing organisms like fish die due to lack of oxygen for release of energyInorganic wasteWaste matter with poisonous materials like lead, mercuryDeath, blinding and paralysis to humans when they eat fish that have consumed matter containing these metals through bioaccumulationDifferences between bioaccumulation and bioamplificationBioaccumulationBioamplificationIncrease in amount (e.g. volume)Increase in concentrationIn an organism’s bodyAcross a food chain(g) outline the roles of microbes in sewage disposal as an example of environmental biotechnologyMolecules or tanks involvedDescriptionType of microbesBacteria and fungusPrimary settling tankUsed water is channelled from households to water reclamation plantsHeavy solids settle to the bottom and removed as sludge in settling plantPartially treated sewage componentSystems involvedDescriptionRemaining used waterAeration tankLiquid is drained and mixed with bacteriaBacteria secrete enzymes to digest organic pollutants to harmless soluble substances and CO2Final settling tankMicroorganisms removed from treated waterRemaining liquid is discharged into seaSludgeAnaerobic digestersSludge is treated with anaerobic digestersDewateringWater is removed and disposed as soil conditioner(h) discuss reasons for conservation of species with reference to the maintenance of biodiversity, management of fisheries and management of timber productionReasonsDescriptionBio-diversityDrugs and insecticidesNearly 25% of medicinal drugs have originated from plant species of rainforests (e.g. Morphine is a pain-supressing drug from poppy plant)Certain poisonous animals in rainforests may contain chemicals with medicinal valueFood provisionRice, pineapple and banana are some examples of food plants developed from rainforest plantsGene poolAgricultural produce can be improved by cross breeding different plant varieties of wild plants and animals of favourable speciesFisheriesPrevent overfishingWhile banning harvesting of endangered species and limiting fishing, fisheries (e.g. hatcheries) raise endangered species and release them into fishing grounds of dwindling fish populationTimber productionIndustriesTropical plants provide raw materials for industries (e.g. rattan used to make furniture, timber for cupboards)Protection of wildlifeForests are a major source of oxygen as well as protection and shade for soilTrees felled for timber have to be cut down at a regular and selective rate to ensure that the functions of forests are not lostUse the knowledge gained in this section in new situations or to solve related problems-End-NoticeWhile every effort has been made to avoid using copyright material, some copyright material may have been inadvertently used in this set of notes. To these copyright holders, we offer our sincere apologies and hope they will take our liberty in good faith. We would welcome any information which would enable us to contact the copyright owners involved.Under the Creative Commons licence,Editors are free to:Share — copy and redistribute the material in any medium or formatAdapt — remix, transform, and build upon the materialUnder the following terms:Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.NonCommercial — You may not use the material for commercial purposes.ShareAlike — If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original.Editors should ensure that any material they wish to embed in this set of notes is not copyrighted before proceeding with editing. ................
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