Biology marking scheme



FORM THREE BIOLOGY 231/1 2019MARKING SCHEMECytology;Microbiology;Entomology;Rej: wrong spellingsUsed for attracting and trapping small animals including rats and mice;Used for keeping collected specimens;Provides living organisms with food nutrients for various life processes in the body;For growth and development;Repair worn out body tissues;Muscular excitation;Ribosomes;Endoplasmic reticulum;Rej: wrong spellings.Length of one cell =diameter of field of view(μm)no.of cells =6000 μm55;= 109.09=109.09 μm;Root hair (cell);D- Cell wall;E- Cell sap /sap vacuole;Controls the functioning of the cell or control cell activities;Arteriosclerosis;Rej: wrong spelling.ARTERIESVEINSHave narrow lumenWide lumenHave no valves(except at bases of pulmonary artery and aorta)Have valves at regular intervalsThick muscular wallsThin and less muscular wallsHave elastic wallsLess elastic wallsN/B: give a mark for two matching answersMonocotyledonous stem; rej stem aloneMonocotyledonae; Rej: wrong spellings.-Absence of cambium/ pith;-Vascular bundles are scattered and not arranged in a ring;Regulation of body temperature;Regulation of PH of body fluids;Defense against diseases causing organisms/ pathogens /infections;Prevent excessive bleeding by enhancing clotting/ prevent excessive loss of blood;Whooping cough-Bordetella pertussis;Pneumonia-Streptococcus pneumonia;Rej: if scientific rules of double naming are not followed.Pneumatophores;It contains numerous lenticels for efficient exchange of gases;It emerges above the soil or water surface for exchange of gases;Has thin epithelium to allow diffusing gases across a short distance;Always moist to dissolve the gases and diffuse in solution form;Has a large surface area for efficient diffusion of gases;Well supplied with blood vessels (highly vasculerised) to maintain a steep concentration gradient;Ventilation mechanism for bringing in air rich in oxygen and expelling air rich in carbon (IV) oxide;SECTION BQ-Sporangiophore;S-Stolon;P -Produces spores for a sexual reproduction;R -For anchorage into the substrate; - Uptake of food nutrients; Rej: uptake of water aloneKingdom fungi;The basic unit is hyphae which collectively form mycelium;Most have cell wall made up of chitin while a few have cellulose cell wall;Have no chloroplast or chlorophyll;They store glycogen or oil droplets but not starch in their cells;They are heterotrophic, feed by means of rhizoids in saprophytes and haustoria in parasites ;( mark 1st three)Pneumatophores/ aerial breathing roots; Rej: wrong spelling. Stomata;T-Gill rakers; (Rej: Gill raker)R-Gill bar/ arch;S-Gill filaments ;( Rej: Gill filament)T- Used to trap food /solid particles to prevent clogging /blocking the gill filaments;S-It is site for gaseous exchange;Highly vasculerised to transport away oxygen that has diffused;Thin epithelium to reduce distance for gases to diffuse across;Are numerous to increases the surface area for maximum absorption of oxygen; (mark the first two).It is to create more room for more haemoglobin to be packed in the cell enabling it to carry more oxygen;Respiration or aerobic respiration;An increase in the temperature on the thermometer reading;Stored starch/ carbohydrates in germinating seeds are broken down/ hydrolysed then oxidized to get energy; some of the energy is released as heat which raises the temperature;To kill bacteria/ fungi/ micro-organisms; that would decay/ decomposition or respiration of micro-organisms which would cause heat;To conserve heat/ prevent heat loss to the surrounding;Use a similar set up with dead disinfected boiled seeds or use dry bean seedsSECTION CScale(S)=(2mks)Plotting(P)=(2mks)Axis(A)=(1mk)Labeling (L)=(1mk)0.403(+ 0.002)10(+ 1%)0.33 percent salt concentration- has less salt concentration/ dilute/ hypotonic than blood cells cytoplasm; water is drawn in by osmosis; the cells swell and eventually burst (a process called haemolysis);0.48 percent salt concentration- concentration of red blood cells cytoplasm is same as the concentration of salt solution (isotonic); therefore, no net movement of water by osmosis; hence cells remained normal and none were haemolysed;0.50% salt concentration is highly concentrated solution /hypertonic than blood cells cytoplasm; red blood cells would lose water by osmosis; shrink and become crenated;The cell sap is more concentrated than the surrounding; water enters into the cell by osmosis; the cell swells/ becomes turgid; but does not burst due to the rigid cellulose cell wall;Enzymes are bio – catalysts (organic catalyst) which are protein in nature;Protein in natureAffected by temperature and pH;Are substrate specific, act in certain specific food substances;Can be used again and again hence required in small amounts;Are catalyst, speed up rate of chemical reactions but are not used up in the reaction; (most enzyme controlled reactions are reversible i.e. they catalyse both forward and backward reactions);Temperature; Enzyme work but within a certain temperature range. Increase in temperature within this range results to increased rate of reaction; Areduction of temperature within this range leads to reduced rate of reaction. At too high temperatures, they become denatured; substrate concentration the higher the concentration of substrate, the faster the rate of reaction, however the rate becomes constant at a certain concentration of substrate, reaction rate remains constant;Enzyme concentration; the higher the concentration of enzymes the faster the rate of reaction;However, when substrate concentration become limiting / few the rate remains constant; The active sites of excess enzymes remains empty hence no corresponding increase in reaction rate;PH- Enzymes work best at optimum pH; above or below this pH enzyme activity drops hence reduced rate of reactions i.e. become denatured.Presence in inhabitation; competition inhibitors compete with the substrate for the enzyme’s active site hence reducing rate of reaction;Non- competitive inhibitors bind on the enzyme changing the shape of the active site. The enzyme cannot bind the substrate hence reducing reaction rate;Produce concentration; if the products of enzymes catalysed reaction are left to accumulate, the rate of reaction slow down; in this situation reverse reaction is favoured;The skin is made up of epidermis and dermis; the epidermis is made up three layers, the outermost layer is known as cornified layer; made up dead cells that protect inner tissues against mechanical damage/ desiccation/ microbes; the granular layer; is made up of living cells that give rise to the cornified layer; the malpighian layer; contain actively dividing cells that give rise to new epidermal cells; it also contains melanin; that protects the skin, give skin pigmentation and protect the skin against ultra-violet rays;The dermis has several components, has sweat glands; that produces sweat; sweat evaporates carrying it with latent heat of vaporization thus reducing the body temperature; under cold conditions little or no sweat is produced; thus heat is conserved; sweat contains water/ sodium chloride /uric acid/ urea; skin being an excretory organ.It has hair; the hair stands erect to trap air when temperature is low to reduce heat loss/ lie flat to allow heat loss when temperature is high;It has nerve endings; which are sensitive to stimuli/ such as heat/ cold/ pain/ pressure/ touch;Has subcutaneous fats/ adipose tissue; to insulate the body against heat loss;Has arteriole (blood capillaries); that vasodilate when temperatures are high to lose heat by radiation/ convection (acc converse).Has sebaceous gland; which secrete sebum; an antiseptic/ water repellant /that prevent drying/ cracking of skin/ make skin supple;Acc blood vessels/blood capillaries for arterioles ................
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