MCAS Biology Review Answer Key

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MCAS Biology Review Answer Key

I. The Chemistry of Life Broad Concept: Chemical elements form organic molecules that interact to perform the basic functions of life.

1. What are the six most common elements in living things? CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur)

2. One of the six elements above is the building block for living things because of its ability to form

covalent bonds with a variety of elements. Which element is this?

carbon

3. Organic molecules form the structures of all living organisms. Fill out the table below:

Organic Molecule

Elements

Building Blocks/Subunits

Functions

Examples

Carbohydrate

C, H, O

Sugars (often end in ?ose)

Short-term energy storage

Glucose, cellulose, starch

Lipid Protein Nucleic Acid

C, H, O

C, H, O, N, sometimes S

and P C, H, O, N, P

Fatty acids and

Long-term energy

triglyceride

storage, cell membrane

Amino acids Nucleotides

Enzymes, transport, communication, structure

Store and transmit genetic information

Waxes, oils, steroids,

phospholipids

helicase, hemoglobin

DNA, RNA

4. What are enzymes, and how do they work? Why are enzymes important? Enzymes are large, complex proteins that speed up chemical reactions by lowering the activation energy. Without enzymes, reactions inside our bodies would take much too long!

5. How does temperature affect enzyme function? How does pH affect enzyme function? Enzymes work faster as the temperature increases, up to a certain point. (If you boil an enzyme, the structure changes ? the enzyme is denatured ? and it no longer works.) Each enzyme works in a particular pH range.

II. Cell Biology Broad Concept: Cells have specific structures and functions that make them distinctive. Processes in a cell can be classified broadly as growth, maintenance, and reproduction.

6. Draw and describe the structure of the plasma membrane. Phospholipid bilayer with embedded proteins... the phospholipids have polar/hydrophilic heads and nonpolar/hydrophobic tails. Some of the proteins extend through the membrane; others are found on the surface only.

7. Why is the plasma membrane important to cells? Controls what enters and exits the cell...small, nonpolar molecules (such as oxygen) easily pass through while larger molecules (such as glucose) need to travel through a protein.

8. What are three structures that all cells have? Plasma membrane, cytoplasm, and genetic material

9. What are three major differences between prokaryotes and eukaryotes? Prokaryotes are smaller, do not contain a nucleus, and do not contain membrane-bound organelles.

10. Give three differences between cell walls and cell membranes. Cell membranes are found in all cells; cell walls are found in plants, fungi, some protists, and some bacteria. Cell membranes are flexible and made of phospholipids; cell walls are rigid and made of cellulose (plants) or chitin (fungi). Cell membranes control what gets in and out of a cell; cell walls provide support and structure.

11. Provide three differences between mitochondria and chloroplasts. Mitochondria make ATP using glucose in cellular respiration; chloroplasts make glucose during photosynthesis. Mitochondria are found in all eukaryotes; chloroplasts are found in plants and some protists only. Mitochondria use oxygen and release carbon dioxide; chloroplasts use carbon dioxide and release oxygen.

12. How does a lysosome differ from a vacuole? A lysosome contains digestive enzymes; a vacuole stores water and other substances.

13. What does the endoplasmic reticulum do? The Golgi apparatus? The endoplasmic reticulum is responsible for transport within the cell (post office) The Golgi apparatus packages materials to be exported out of the cell (UPS)

14. What is osmosis? Diffusion of water from areas of high water concentration (hypotonic) to areas of low water concentration (hypertonic). Water follows the solutes!

15. Provide two differences between simple diffusion and active transport.

Simple diffusion is passive, meaning the molecules move from high to low concentration without

the use of energy. Active transport requires energy and molecules move through a membrane

protein.

16. Complete the chart below for each of the six kingdoms:

Kingdom

Prokaryote or Eukaryote?

Autotrophs or heterotrophs?

Unicellular or multicellular?

Examples

Prokaryote

Both

Unicellular

Archaeabacteria

Methanogens

Eubacteria Protista Fungi Plantae Animalia

Prokaryote Eukaryote Eukaryote Eukaryote Eukaroyote

Both

Both

Heterotrophs (decomposers)

Autotrophs

Unicellular

Both

Multicellular (except yeast) Multicellular

E. coli

Algae, paramecium, euglena

Mushrooms, mold, yeast Trees, flowers, ferns

Heterotrophs

Multicellular

Worms, spiders, sharks, humans

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17. Give the equation for photosynthesis in words and chemical symbols. Why is photosynthesis important? CO2 + H2O + E C6H12O6 + O2 / carb?n dioxide + w?ter + light energy glucose + oxygen Photosynthesis provides all of the chemical energy for an ecosystem. Also supplies oxygen.

18. Give the equation for cellular respiration in words and chemical symbols. Why is cellular respiration important? C6H12O6 + O2 ATP + CO2 + H2O / glucose + oxygen ATP + carb?n dioxide + w?ter Cellular respiration allows all organisms to make ATP, which is energy that is necessary to power many types of chemical reactions in cells

19. Which kingdoms contain organisms that undergo cellular respiration? Which kingdoms contain organisms that undergo photosynthesis? All organisms undergo cellular respiration. Some bacteria, some protists, and all plants undergo photosynthesis

20. What is ATP? Why is it important to living things? ATP = adenosine triphosphate Energy transfer molecule for living organisms; made during cellular respiration and then used in chemical reactions such as protein synthesis, mitosis, and active transport.

21. Provide three differences between mitosis and meiosis. Mitosis goes through 1 division; meiosis involves 2 divisions. Mitosis produces 2 identical cells; meiosis produces 4 unique cells. Mitosis is used for growth and repair; meiosis is used for creation of gametes (sex cells). Mitosis produces diploid cells; meiosis produces haploid cells.

22. What is interphase? Stage of the cell cycle when the cell is metabolically active, is growing, and is preparing to divide by undergoing DNA replication.

23. What is cytokinesis? Division on the cytoplasm; follows mitosis.

24. How are gametes different from other cells? Gametes are haploid (contain half the number of chromosomes ? one from each pair)

25. What happens during fertilization? What is a zygote? Egg (female gamete) and sperm (male gamete) come together and the nuclei fuse, creating a zygote. The gametes are haploid (ex ? 23 chromosomes) and the resulting zygote is diploid (ex ? 46 chromosomes). The zygote can then undergo mitosis to grow into a multicellular organism.

26. What is the structure of a typical virus? Genetic material surrounded by a protein coat. (NOT a cell!)

27. How does a virus typically reproduce? A virus invades a host cell and then uses the host cells enzymes and ribosomes to create more copies of the genetic material (DNA or RNA) and new protein coats. The new viruses are then assembled within the host cell, and then the viruses break free from the host cell and infect new cells.

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III. Genetics Broad Concept: Genes allow for the storage and transmission of genetic information. They are a set of instructions encoded in the nucleotide sequence of each organism. Genes code for the specific sequences of amino acids that comprise the proteins that are characteristic of that organism.

28. Describe the structure of DNA, including the structure of its subunits. DNA is a double helix made of repeating units of nucelotides. Each nucleotide consists of a sugar (deoxyribose), a phosphate, and a nitrogen base. The two strands of DNA are complementary. The backbone of the double helix is made of sugar-phosphate bonds. Nitrogen bases hold the two strands of DNA together.

29. What are the four DNA bases and their one-letter abbreviations? A = adenine; T = thymine; C = cytosine; G = guanine

30. Why is DNA important to living things? Stores all genetic information, which means it codes for all proteins. Enables information to be passed down from one generation to the next.

31. How is DNA replicated? List the steps and identify one key enzyme. Double helix is unwound by helicase. Each strand acts as a template for building the new strand. DNA polymerase adds new nucleotides (A-T and C-G). This is known as semiconservative replication.

32. Give the complementary strand for this strand of DNA: ATTAGCGAGATC TAATCGCTCTAG

33. How does DNA differ from RNA? Provide three differences. DNA is double-stranded; RNA is single-stranded. DNA has thymine (T); RNA has uracil (U). DNA has deoxyribose sugar; RNA has ribose sugar. DNA cannot leave the nucleus; RNA is found throughout the cell.

34. List the three types of RNA. What is the function of each? Messenger (mRNA) ? brings DNA code from the nucleus to the ribosome Transfer (tRNA) ? carries amino acids to the ribosome to form polypeptide chain Ribosomal (rRNA) ? makes up the ribosome, along with proteins

35. Protein synthesis describes the flow of genetic information from gene to protein, and includes two

key steps, transcription and translation. Fill in the chart below:

Process

Starting Material

End Product

Location

Transcription

DNA

mRNA

Nucleus

Translation

mRNA and free amino acids attached to tRNA

Amino acid chain (polypeptide chain)

Ribosome in cytoplasm

36. Transcribe this DNA strand into mRNA: TGTCCATAGCTC ACAGGUAUCGAG

37. Use a genetic code chart or wheel to translate this mRNA strand into the amino acids: AUGGCGUUCACA Methionine ? Alanine ? Phenylalanine - Threonine

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38. Do all genetic mutations cause phenotypic changes (changes in the proteins that are made)? Why or why not? NO ? some genetic mutations are silent, which means that although the DNA is changed, the amino acid is not changed so the protein stays the same

39. Are all genetic mutations bad? Explain why or why not? No, some mutations may be beneficial, such as improving eyesight, etc.

40. Assume T = tall plants and t = short plants. Which of these alleles is dominant and which is recessive? What does this mean? T (tall) is dominant (capital letter) whereas t (short) is recessive. The dominant trait (tall) will mask the recessive trait (short) in a heterozygous individual.

41. What is the difference between a plant that is homozygous tall and a plant that is heterozygous tall? Homozygous tall = TT (2 dominant); Heterozygous tall = Tt (1 dominant, 1 recessive)

42. Use a Punnett square to show the expected results of a cross between two heterozygous tall plants. Tt x Tt T t T TT Tt t Tt tt

43. Explain Mendel's law of segregation. The alleles for a gene separate during meiosis because the chromosome pairs separate during meiosis.

44. Explain Mendel's law of independent assortment. The alleles for one gene separate independently from alleles for another trait on a different chromosome pair. This increases genetic diversity because each gamete can receive many different combinations of alleles (chromosomes).

45. How many unique gamete possibilities exist from a parent with the genotype AaBb? Identify each. 4 unique gametes: AB, Ab, aB, ab (each gamete would receive one allele for each gene)

46. What is incomplete dominance? Give an example. Neither allele is dominant; the results are blended. Ex - red flower x white flower = pink flower

47. What is codominance? Give an example. Both alleles are dominant; both traits can be seen. Ex - black cat x white cat = spotted cat

48. What are polygenic traits? Give an example. Traits controlled by many genes. Ex - hair color, eye color, skin color.

49. What are sex-linked traits? Give an example. Gene is found on the X chromosome. (Females are XX; males are XY.) These traits are more common among males. Ex ? red-green colorblindness, hemophilia

50. Why are human blood types considered "multiple allele" traits? There are 3 different alleles: IA, IB, and i (or A, B, and O)

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IV. Anatomy Broad Concept: There is a relationship between the organization of cells into tissues, and tissues into organs. The structure and function of organs determine their relationships within body systems or an organism. Homeostasis allows the body to perform its normal functions.

51. Explain how the digestive system (mouth, pharynx, esophagus, stomach, small intestine, large intestine, and rectum, with the aid of the liver, gall bladder, and pancreas) would convert macromolecules from a ham and cheese sandwich into smaller molecules that can be used by cells for energy and for repair and growth. Mechanical digestion begins in the mouth; the pharynx produces salivary amylase that starts chemical digestion. Food travels through the esophagus to the stomach, where the acidic pH and pepsin continue digestion. Food then enters the small intestine, where digestion is completed with the help of the liver (bile ? stored in the gall bladder) and pancreas (pancreatic enzymes). Nutrients are absorbed in the small intestine, and then food passes into the large intestine where water can be absorbed. Solid waste is stored in the rectum until it can be eliminated.

52. Explain how the circulatory system (heart, arteries, veins, capillaries, red blood cells) transports nutrients and oxygen to cells and removes cell wastes. The heart is a muscular pump that is responsible for moving blood throughout the arteries (away from the heart), into capillaries, and then back to the heart through the veins. The capillaries are only one-cell thick, so oxygen and nutrients and diffuse into body cells and carbon dioxide and wastes can diffuse back into the blood cells. Red blood cells contain hemoglobin, which binds oxygen.

53. How are the kidneys closely related to the circulatory system? The kidneys filter waste from the blood and create urine, which is stored in the bladder. The kidneys also help to regulate the water level of blood.

54. What role does the liver play in digestion? What role does the liver play with the circulatory system? The liver produces bile, which helps to break down and absorb fats. The liver also filters out toxins from the blood.

55. Explain how the respiratory system (nose, pharynx, larynx, trachea, lungs, alveoli) provides exchange of oxygen and carbon dioxide. Air enters the body through the nose and pharynx, passes the larynx where sound can be produced, into the trachea and bronchi, and then enters the lungs. The alveoli are small air sacs within the lungs where gas exchange occurs. Oxygen diffuses from the alveolil into the capillaries, and carbon dioxide diffuses from the capillaries into the alveoli. The diaphragm is the muscle that allows breathing to happen.

56. What is the difference between the central nervous system and the peripheral nervous system? The central nervous system consists of the brain and spinal cord; the peripheral nervous system contains all of the nerves that connect the CNS with the rest of the body.

57. Draw a neuron, label the parts (dendrites, cell body, axon, axon terminal) and explain generally how it transmits messages. The dendrite receives a chemical signal (neurotransmitters) and sends an electrical signal down the axon, which causes the axon terminal to release more neurotransmitters, hence electrochemical signaling!

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58. Explain the differences between the skeletal, smooth, and cardiac muscle. Skeletal muscle is voluntarily controlled; smooth and cardiac muscle are involuntarily controlled by the autonomic nervous system. Both skeletal and cardiac muscle are striated (striped).

59. Explain how the muscular/skeletal system (skeletal muscle, bones, cartilage, ligaments, tendons) works with other systems to support and allow for movement. The skeletal muscle uses the bones as levers to allow for movement. Bone also provide support and protection. Cartilage acts as a cushion and site for new bone growth. Ligaments connect two bones together. Tendons connect bone to muscle.

60. Where are red and white blood cells produced? In the bone marrow (spongy part of long bones)

61. How does the sexual reproductive system allow organisms to produce offspring that resemble, but are not identical to, either of their parents? Gametes are formed by meiosis in the gonads (testes or ovaries). Gametes only contain half the number of chromosomes, so when a zygote is formed during fertilization, half of the chromosomes come from the father and half from the mother.

62. The human body has two major communication systems. Explain how the body uses both electrochemical signals and chemical signals (hormones) to communicate messages from one part of the body to cell to cells in another part of the body? Electrochemical signals occur in the nervous system between two neurons or a neuron and muscle or gland. Hormones are produced by endocrine glands and travel long distances through the blood stream to send a message. Hormones can affect many target cells at once.

63. The body's systems interact to maintain homeostasis. Describe the basic function of a physiological feedback loop using the following example: The brain monitors the concentration of solutes in the blood and sends signals to key organs to maintain water balance. If the brain detects that there is too much water in the blood, a message will be sent to the kidneys to absorb more water from the blood. Once the acceptable water level is reached, the brain receives that information and then cancels the message to the kidneys to absorb more water.

V. Evolution and Biodiversity Broad Concept: Evolution is the results of genetic changes that occur in constantly changing environments. Over many generations, changes in the genetic make-up of populations may affect biodiversity through speciation and extinction.

64. What is meant by the term "evolution"? Genetic changes in a population over a long period of time

65. Identify and describe the four principles of Darwin's theory of natural selection using the following example: Millions of years ago, the ancestors of giraffes had shorter necks. Today, giraffes have longer necks that allow them to eat leaves that other animals cannot reach. Variation: some giraffes had shorter necks, and others had longer necks Heritability: the gene for neck length is passed from one generation to the next Overpopulation: the giraffes with shorter necks had to compete with other animals for food and were less likely to survive and reproduce Reproductive Advantage: the giraffes with longer necks were able to get enough food more easily, and they were able to survive and reproduce, passing on the gene for long necks

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66. Explain why the fossil record is useful in supporting evolution. Allows scientists to compare species that once lived with species that are now alive. Also allows scientists to compare organisms as they changed over time.

67. Explain how comparing skeletons and body parts can help explain evolution. Homologous structures, such as the limb bones of vertebrates, show that species came from a common ancestor. (Human arm, bat wing, and whale fin all have very similar bone structure despite their different functions.)

68. Explain how recent advances in genetics and molecular biology support evolution, even though Darwin didn't have access to this information. By comparing DNA and amino acid sequences, scientists can see how closely related two species are (more similarities = closer relationship). Darwin made these observations based on physical evidence; the genetic evidence supports everything else.

69. What are homologous structures? Give three examples. Homologous structures show similarities due to common ancestry. Ex ? limb bones, number of neck vertebrae, mollusk "feet"

70. What is a vestigial organ? Give two examples in humans and one in another animal. Vestigial organs do not have a current known function but show history because an ancestor had this organ and it functioned. Ex ? appendix, tailbone, femur in whale

71. Define "species." A group of organisms of the same type that can successfully reproduce with one another

72. Fill in the blanks: Domain - kingdom - phylum - class ? order ? family ? genus ? species

73. Explain how two populations of finches separated on different islands can evolve into different species over many generations. Each population will adapt to the different niches on the island. Because the two populations are separated, there is no exchange of genes between the two groups. A beneficial trait that appears in one population may not appear in the other, and over many generations the two groups will become so different that they can no longer interbreed.

74. How can evolution increase biodiversity in an area? Evolution can increase biodiversity through speciation (the creation of new species).

VI. Ecology Broad Concept: Ecology is the interaction among organisms and between organisms and their environment.

75. Explain how immigration and emigration change the size of a given population. Immigration will decrease a population's size because individuals are leaving an area. Emigration will increase a population's size because new individuals are entering an area.

76. Explain what happens to a population if too many offspring are born, or if too many members die. If too many offspring are born, not all will survive because there will not be enough resources. If too many members die, the population will decrease but may level out because there will be lots of resources for the remaining members.

77. What is extinction? Provide three causes of extinction. Loss of a species caused by... habitat loss, climate change, overfishing, invasive species, etc

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