AP Biology Essay Questions
The following is a comprehensive list of essay questions that have been asked on past AP exams. The questions are organized according to units.
Unit 1 (Basic Chemistry and Water)
1. The unique properties (characteristics) of water make life possible on Earth. Select three properties of water and:
Unit 2 (Organic Chemistry, Biochemistry, and Metabolism)
2. Describe the chemical composition and configuration of enzymes and discuss the factors that modify enzyme structure and/or function.
3. After an enzyme is mixed with its substrate, the amount of product formed is determined at 10-second intervals for 1 minute. Data from this experiment are shown below:
Draw a graph of these data and answer the following questions.
4. Enzymes are biological catalysts.
Unit 3 (Cell Structure and Function, Cell division)
5. Describe the fluid-mosaic model of a plasma membrane. Discuss the role of the membrane in the movement of materials through it by each of the following processes:
6. Describe the structure of a eukaryotic plant cell. Indicate the ways in which a nonphotosynthetic prokaryotic cell would differ in structure from this generalized eukaryotic plant cell.
7. Discuss the process of cell division in animals. Include a description of mitosis and cytokinesis, and of the other phases of the cell cycle. Do Not include meiosis.
8. A laboratory assistant prepared solution of 0.8 M, 0.6 M, 0.4 M, and 0.2 M sucrose, but forgot to label them. After realizing the error, the assistant randomly labeled the flasks containing these four unknown solutions as flask A, flask B, flask C, and flask D.
Design an experiment, based on the principles of diffusion and osmosis, that the assistant could use to determine which of the flasks contains each of the four unknown solutions. Include in your answer (a) a description of how you would set up and perform the experiment: (b) the results you would expect from your experiments: and (c) an explanation of those results based on the principles involved. (Be sure to clearly state the principles addressed in your discussion.)
9. Cells transport substances across their membranes. Choose THREE of the following four types of cellular transport.
For each of the three transport types you choose,
Unit 4 (Photosynthesis and Cellular Respiration)
10. Describe the similarities and differences between the biochemical pathways of aerobic respiration and photosynthesis in eukaryotic cells. Include in your discussion the major reactions, the end products, and energy transfers.
11. The rate of photosynthesis may vary with changes that occur in environmental temperature, wavelength of light, and light intensity. Using a photosynthetic organism of your choice, choose only ONE of the three variables (temperature, wavelength of light, or light intensity) and for this variable
12. Describe the light reactions of photosynthesis and, for both a C3 and a C4 plant, trace the path of a carbon dioxide molecule from the point at which it enters a plant to its incorporation into a glucose molecule. Include leaf anatomy and biochemical pathways in your discussion of each type of plant.
13. Explain what occurs during the Krebs (citric acid) cycle and electron transport by describing the following:
14. Membranes are important structural features of cells.
15. Energy transfer occurs in all cellular activities. For 3 of the following 5 processes involving energy transfer, explain how each functions in the cell and give an example. Explain how ATP is involved in each example you choose.
16. The results below are measurements of cumulative oxygen consumption by germinating and dry seeds. Gas volume measurements were corrected for changes in temperature and pressure.
Unit 5 (Meiosis, Mendelian Genetics, DNA Replication)
17. State the conclusions reached by Mendel in his work on the inheritance of characteristics. Explain how each of the following deviates from these conclusions.
18. Experiments by the following scientists provided critical information concerning DNA. Describe each classical experiment and indicate how it provided evidence for the chemical nature of the gene.
19. Discuss Mendel’s laws of segregation and independent assortment. Explain how the events of meiosis I account for the observations that led Mendel to formulate these laws.
20. An organism is heterozygous at two genetic loci on different chromosomes.
Labeled diagrams that are explained in your answer may be useful.
Unit 6 (Protein Synthesis, Gene Expression, DNA Technology)
21. A portion of specific DNA molecule consists of the following sequence of nucleotide triplets.
TAC GAA CTT GGG TCC
This DNA sequence codes for the following short polypeptide.
methionine – leucine – glutamic acid – proline – arginine
Describe the steps in the synthesis of this polypeptide. What would be the effect of a deletion or an addition in one of the DNA nucleotides? What would be the effects of a substitution in one of the nucleotides?
22. Describe the operon hypothesis and discuss how it explains the control of messenger RNA production and the regulation of protein synthesis in bacterial cells.
23. Scientists seeking to determine which molecule is responsible for the transmission of characteristics from one generation to the next knew that the molecule must (1) copy itself precisely, (2) be stable but able to be changed, and (3) be complex enough to determine the organism’s phenotype.
24. Describe the biochemical composition, structure, and replication of DNA. Discuss how recombinant DNA techniques may be used to correct a point mutation.
25. Describe the production and processing of a protein that will be exported from a eukaryotic cell. Begin with the separation of the messenger RNA from the DNA template and end with the release of the protein at the plasma membrane.
26. Describe the steps of protein synthesis, beginning with the attachment of a messenger RNA molecule to the small subunit of a ribosome and ending generalized with the release of the polypeptide from the ribosome. Include in your answer a discussion of how the different types of RNA function in this process.
27. The diagram below shows a segment of DNA with a total length of 4,900 base pairs. The arrows indicate reaction sites for two restriction enzymes (enzyme X and enzyme Y).
28. By using the techniques of genetic engineering, scientists are able to modify genetic materials so that a particular gene of interest from one cell can be incorporated into a different cell.
29. Assume that a particular genetic condition in a mammalian species causes an inability to digest starch. This disorder occurs with equal frequency in males and females. In most cases, neither parent of affected offspring has the condition.
Unit 7 (Evolution, Population Genetics, Speciation)
29. Describe the special relationship between the two terms in each of the following pairs.
30. Describe the modern theory of evolution and discuss how it is supported by evidence from two of the following areas.
31. Describe the process of speciation. Include in your discussion the factors that may contribute to the maintenance of genetic isolation.
32. Do the following with reference to the Hardy-Weinberg model.
33. Evolution is one of the major unifying themes of modern biology.
34. Genetic variation is the raw material for evolution.
35. In a laboratory population of diploid, sexually reproducing organisms a certain trait is studied. This trait is determined by a single autosomal gene and is expressed as two phenotypes. A new population was created by crossing 51 pure breeding (homozygous) dominant individuals with 49 pure breeding (homozygous) individuals. After four generations, the following results were obtained.
Unit 8 (Chemical Evolution, Prokaryotes, Eukaryote Evolution, Protista)
36. Scientists recently have proposed a reorganization of the phylogenetic system of classification to include the domain, a new taxonomic category higher (more inclusive) than the Kingdom category, as shown in the following diagram.
Domain Bacteria Domain Archaea Domain Eukarya
(Eubacteria) (Archaebacteria) (Eukaryotes)
Unit 9 (Introduction to Plants, Fungi, Invertebrates)
37. In the life cycles of a fern and a flowering plant, compare and contrast each of the following:
38. Describe the differences between the terms in each of the following pairs.
Unit 10 (Vertebrates, Basic Animal Structure and Function)
39. Select two of the following three pairs and discuss the evolutionary relationships between the two members of each pair you have chosen. In your discussion include structural adaptations and the functional significance.
Pair A: green algae—vascular plants
Pair B: prokaryotes—eukaryotes
Pair C: amphibians—reptiles
Unit 11 (Animal Nutrition, Circulation, Respiration, Immune System)
40. Describe the structure of a mammalian respiratory system. Include in your discussion the mechanisms of inspiration and expiration.
41. Describe the processes of fat and protein digestion and product absorption as they occur in the human stomach and small intestine. Include a discussion of the enzymatic reactions involved.
42. Describe the following mechanisms of response to foreign materials in the human body.
43. Discuss the processes of exchange of O2 and CO2 that occur at the alveoli and muscle cells of mammals. Include in your answer a description of the transport of these gases in the blood.
44. Many physioligical changes occur during exercise.
45. The graph below shows the response of the human immune system to exposure to an antigen. Use this graph to answer part a and part b of this question.
Unit 12 (Homeostasis, Reproduction, Development)
47. Discuss the processes of cleavage, gastrulation, and neurulation in the frog embryo; tell what each process accomplishes. Describe an experiment that illustrates the importance of induction in development.
48. The evolutionary success of organisms depends on reproduction. Some groups of organisms reproduce asexually, some reproduce sexually, while others reproduce both sexually and asexually.
Unit 13 (Endocrine System, Nervous System, Sensory and Motor Mechanisms)
49. Discuss the sources and actions of each of the following pairs of hormones in humans and describe the feedback mechanisms that control their release.
50. Beginning at the presynaptic membrane of the neuromuscular junction, describe the physical and biochemical events involved in the contraction of a skeletal muscle fiber. Include the structure of the fiber in your discussion.
52. Describe the negative and positive feedback loops, and discuss how feedback mechanisms regulate each of the following.
53. Discuss how cellular structures, including the plasma membrane, specialized endoplasmic reticulum, cytoskeletal elements, and mitochondria, function together in the contraction of skeletal muscle cells.
54. Structure and function are related in the various organ systems of animals. Select two of the following four organ systems in vertebrates:
For each of the two systems you choose, discuss the structure and function of two adaptations that aid in the transport or exchange of molecules (or ions). Be sure to relate structure to function in each example.
Unit 14 (Plant Structure and Function)
55. Relate the structure of an angiosperm leaf to each of the following:
56. Define the following plant responses and explain the mechanism of control for each. Cite experimental evidence as part of your discussion.
57. Describe the structure of a bean seed and discuss its germination to the seedling stage. Include in your essay hormonal controls, structural changes, and tissue differentiation.
58. Describe the effects of plant hormones on plant growth and development. Design an experiment to demonstrate the effect of one of these plant hormones on plant growth and development.
59. Trace the pathway in a flowering plant as the water moves from the soil through the tissues of the root, stem, and leaves to the atmosphere. Explain the mechanisms involved in conducting water through these tissues.
60. Discuss the adaptations that have enabled flowering plants to overcome the following problems associated with life on land.
61. A group of students designed an experiment to measure transpiration rates in a particular species of herbaceous plant. Plants were divided into four groups and were exposed to the following conditions.
The cumulative water loss due to transpiration of water from each plant was measured at 10-minute intervals for 30 minutes. Water loss was expressed as milliliters of water per square centimeter of leaf surface area. The data for all plants in Group I (room conditions) were averaged. The average cumulative water loss by the plants in Group I is presented in the table below.
62. Numerous environmental variables influence plant growth. Three students each planted a seedling of the same genetic variety in the same type of container with equal amounts of soil from the same source. Their goal was to maximize their seedling’s growth by manipulating environmental conditions. Their data are shown below.
Unit 15 (Ecology)
63. Define and explain the role of each of the following in social behavior.
64. Describe the trophic levels in a typical ecosystem. Discuss the flow of energy through the ecosystem, the relationship between the different trophic levels, and the factors that limit the number of trophic levels.
65. Describe and give an example of each of the following. Include in your discussion the selection advantage of each.
66. Describe the process of ecological succession from a pioneer community to a climax community. Include in your answer a discussion of species diversity and interactions, accumulation of biomass, and energy flow.
67. Describe releasers, imprinting, and communications, as each of these terms relates to animal behavior. You may include in your answer a discussion of the classical studies of Niko Tinbergen, Konrad Lorenz, and Karl von Frisch.
68. Describe the biogeochemical cycles of carbon and nitrogen. Trace these elements from the point of their release from a decaying animal to their incorporation into a living animal.
69. Using an example for each, discuss the following ecological concepts.
70. Living organisms play an important role in the recycling of many elements within an ecosystem. Discuss how various types of organisms and their biochemical reactions contribute to the recycling of either carbon or nitrogen in an ecosystem. Include in your answer one way in which human activity has an impact in the nutrient cycle you have chosen.
71. Survival depends on the ability of an organism to respond to changes in its environment. Some plants flower in response to changes in day length. Some mammals may run or fight when frightened. For both of these examples, describe the physiological mechanisms involved in the response.
72. Interdependence in nature is illustrated by the transfer of energy through trophic levels. The diagram below depicts the transfer of energy in a food web of an Arctic lake located in Alaska (J )
For the data above, provide information on each of the following.
Choose ONE of the variables that you identified and design a controlled experiment to test your hypothetical explanation. Describe results that would support or refute your hypothesis.
74. Describe how the following adaptations have increased the evolutionary success of the organisms that possess them. Include in your discussion the structure and function related to each adaptation.
75. Describe the anatomical and functional similarities and difference within each of the following pairs of structures.
76. Discuss how each of the following has contributed to the evolutionary success of the organisms in which they are found.
77. Angiosperms (flowering plants) and vertebrates obtain nutrients from their environment in different ways.
78. The problem of survival of animals on land are very different from those of survival of animals in an aquatic environment. Describe four problems associated with animal survival in terrestrial environments but not in aquatic environments. For each problem, explain an evolutionary solution.
79. The survival of organisms depends on regulatory mechanisms at various levels. Choose THREE from the following examples. Explain how each is regulated.
80. Photosynthesis and cellular respiration recycle oxygen in ecosystems. Respond to TWO (and only two) of the following:
81. Biological recognition is important in many processes at the molecular, cellular, tissue, and organismal levels. Select three of the following, and for each of the three that you have chose, explain how the process of recognition occurs and give an example of each.
82. Communication occurs among the cells in a multicellular organism. Choose THREE of the following examples of cell-to-cell communication, and for each example, describe the communication that occurs and the types of responses that result from this communication.