Ap Bio Essays Topic

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:

    1. for each property, identify and define the property and explain it in terms of the physical/chemical nature of water.
    2. for each property, describe one example of how the property affects the functioning of living organisms.

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:

    Time (sec)








    Product formed (mg)








    Draw a graph of these data and answer the following questions.

    1. What is the initial rate of this enzymatic reaction?
    2. What is the rate after 50 seconds? Why is it different from the initial rate?
    3. What would be the effect on product formation if the enzyme where heated to a temperature of 100° C for 10 minutes before repeating the experiment? Why?
    4. How might altering the substrate concentration affect the rate of the reaction? Why?
    5. How might altering the pH affect the rate of the reaction? Why?

4.  Enzymes are biological catalysts.

    1. Relate the chemical structure of an enzyme to its specificity and catalytic activity.
    2. Design a quantitative experiment to investigate the influence of pH or temperature on the activity of an enzyme.
    3. Describe what information concerning the structure of an enzyme could be inferred from your experiments.

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:

    1. Active transport
    2. Passive transport

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.

    • Osmosis
    • Active Transport
    • Facilitated Diffusion
    • Endocytosis/exocytosis

For each of the three transport types you choose,

    1. Describe the transport process and explain how the organization of cell membranes functions in the movement of specific molecules across membranes; and
    2. Explain the significance of each type of transport to a specific cell (you may use difference cell types as examples.)

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

    • design a scientific experiment to determine the effect of the variable on the rate of photosynthesis for the organism;
    • explain how you would measure the rate of photosynthesis in your experiment;
    • describe the results you would expect. Explain why you would expect these results.

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:

    1. The location of the Krebs cycle and electron transport chain in mitochondria.
    2. The cyclic nature of the reactions in the Krebs cycle.
    3. The production of ATP and reduced coenzymes during the cycle.
    4. The chemiosmotic production of ATP during electron transport.

14.  Membranes are important structural features of cells.

    1. Describe how membrane structure is related to the transport of materials across the membrane.
    2. Describe the role of membranes in the synthesis of ATP in either cellular respiration or photosynthesis.

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.

        • cellular movement
        • active transport
        • synthesis of molecules
        • chemiosmosis
        • fermentation

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.

    Cumulative Oxygen Consumed (mL)

    Time (minutes)






    22° C Germinating Seeds






    Dry Seeds






    10° C Germinating Seeds






    Dry Seeds






    1. Using the graph paper provided, plot the results for the germinating seeds at 22° C and at 10° C.
    2. Calculate function the rate of oxygen consumption for the germinating seeds at 22° C, using the time interval between 10 and 20 minutes.
    3. Account for the differences in oxygen consumption observed between:
      1. germinating seeds at 22° C and at 10° C
      2. germinating seeds and dry seeds
    4. Describe the essential features of an experimental apparatus that could be used to measure oxygen consumption by a small organism. Explain why each of these features is necessary.

    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.

    1. Autosomal linkage.
    2. Sex-linked (X-linked) inheritance.
    3. Polygenic (multiple-gene) inheritance.

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.

    1. Hershey and Chase- bacteriophage replication
    2. Griffith and Avery, MacLeod and McCarty- bacterial transformation
    3. Meselson and Stahl- DNA replication in bacteria

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.

    1. Explain how these alleles are transmitted by the process of mitosis to daughter cells.
    2. Explain how these alleles are distributed by the process of meiosis to gametes.
    3. Explain how the behavior of these two pairs of homologous chromosomes during meiosis provides the physical basis for Mendel’s two laws of inheritance.

    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.


    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.

  • Explain how DNA meets each of the three criteria stated above.
  • Select one of the criteria stated above and describe experimental evidence used to determine that DNA is the hereditary material.


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).

    1. Explain how the principles of gel electrophoresis allow for the separation of DNA fragments.
    2. Describe the results you would expect from the electrophoresis separation of fragments from the following treatments of the DNA segment above. Assume that the digestions occurred under appropriate conditions and went to completion.
      1. DNA digested with only enzyme X
      2. DNA digested with only enzyme Y
      3. DNA digested with enzyme X and enzyme Y combined
      4. Undigested DNA
    3. Explain both of the following.
      1. The mechanism of action of restriction enzymes.
      2. The different results you would expect if a mutation occurred at the recognition site for 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.

        • Describe a procedure by which this can be done.
        • Explain the purpose of each step of your procedure.
        • Describe how you could determine whether the gene was successfully incorporated.
        • Describe an example of how gene transfer and incorporation have been used in biomedical or commercial applications.

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.

    1. Describe the most probable pattern of inheritance for this condition. Explain your reasoning. Include in your discussion a sample cross(es) sufficient to verify your proposed pattern.
    2. Explain how a mutation could cause this inability to digest starch.
    3. Describe how modern techniques of molecular biology could be used to determine whether the mutant allele is present in a given individual.

    Unit 7 (Evolution, Population Genetics, Speciation)

29.  Describe the special relationship between the two terms in each of the following pairs.

    1. Convergent evolution of organisms and Australia.
    2. Blood groups and genetic drift.
    3. Birds of prey and DDT.

30.  Describe the modern theory of evolution and discuss how it is supported by evidence from two of the following areas.

    1. population genetics
    2. molecular biology
    3. comparative anatomy and embryology

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.

    1. Indicate the conditions under which allelic frequencies (p and q) remain constant from one generation to the next.
    2. Calculate, showing all work, the frequencies of the alleles and the frequencies of the genotypes in a population of 100,000 rabbits, of which 25,000 are white and 75,000 are agouti. (In rabbits the white color is due to a recessive allele, w, and the agouti is due to a dominant all, W.)
    3. If the homozygous dominant condition were to become lethal, what would happen to the allelic and genotypic frequencies in the rabbit population after two generations?

33.  Evolution is one of the major unifying themes of modern biology.

    1. Explain the mechanisms that lead to evolutionary change.
    2. Describe how scientists use each of the following as evidence for evolution.
      1. Bacterial resistance to antibodies.
      2. Comparative biochemistry.
      3. The fossil record.

34.  Genetic variation is the raw material for evolution.

    1. Explain three cellular and/or molecular mechanisms that introduce variation into the gene pool of a plant or animal population.
    2. Explain the evolutionary mechanisms that can change the composition of the gene pool.

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.

    Number of Individuals

























    1. Identify an organism that might have been used to perform this experiment, and explain why this organism is a good choice for conducting this experiment.
    2. On the basis of the data, propose a hypothesis that explains the change in phenotypic frequency between generation 1 and generation 3.
    3. Is there evidence indicating whether or not this population is in Hardy-Weinberg equilibrium? Explain.

 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.

Universal Ancestor

Domain Bacteria             Domain Archaea Domain Eukarya

(Eubacteria)             (Archaebacteria) (Eukaryotes)


    • describe how this classification scheme presents different conclusions about the relationships among living organisms than those presented by the previous five-kingdom system of classification
    • describe three kinds of evidence that were used to develop the taxonomic scheme above, and explain how this evidence was used. The evidence may be structural, physiological, molecular, and/or genetic.
    • Describe
    • four of the characteristics of the universal ancestor.

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:

    1. The gametophyte generation.
    2. Sperm transport and fertilization.
    3. Embryo protection.

38.  Describe the differences between the terms in each of the following pairs.

    1. Coelomate versus acoelomate body plan.
    2. Protostome versus deuterostome development.
    3. Radial versus bilateral symmetry.
    4. Explain how each of these pairs of features was important in constructing the phylogenetic tree shown below. Use specific examples from the tree in your discussion.

    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.

    1. The antigen-antibody response to a skin graft from another person.
    2. The reactions of the body leading to inflammation of a wound infected by bacteria.

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.

    1. Design a controlled experiment to test the hypothesis that an exercise session causes short-term increases in heart rat and breathing rate in humans.
    2. Explain how at least three organ systems are affected by this increased physical activity and discuss interactions among these systems.

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.

    1. Describe the events that occur during period I as the immune system responds to the initial exposure to the antigen.
    2. Describe the events that occur during period II following a second exposure to the same antigen.
    3. Explain how infection by the AIDS virus (HIV) affects the function of both T and B lymphocytes.

    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.

    1. Using THREE difference organisms, give an example of one organism that reproduces sexually, one that reproduces asexually, and one that reproduces BOTH sexually and asexually. For each organism given as an example, describe two reproductive adaptations. These adaptations may be behavioral, structural, and/or functional.
    2. What environmental conditions would favor sexual reproduction? Explain. What environmental conditions would favor asexual reproduction? Explain.

    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.

    1. Insulin—glucagon
    2. Parathyroid hormone—calcitonin
    3. Thyrotropin (TSH)—thyroxine (T4)

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.

    1. The menstrual cycle in nonpregnant human female.
    2. Blood glucose levels in humans.

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:

    • respiratory
    • digestive
    • excretory
    • nervous

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:

    1. Adaptations for photosynthesis and food storage.
    2. Adaptations for food translocation and water transport.
    3. Specialized adaptations to a desert environment.

56.  Define the following plant responses and explain the mechanism of control for each. Cite experimental evidence as part of your discussion.

    1. Phototropism
    2. Photoperiodism

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.

    1. The absence of an aquatic environment for reproduction.
    2. The absence of an aquatic environment to support the plant body.
    3. Dehydration of the plant.

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.

    Group I-Room conditions (light, low humidity, 20° C, and little air movement.)
    Group II-Room conditions with increased humidity.
    Group III-Room conditions with increased air movement (fan)
    Group IV-Room conditions with additional light

    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.

    Average Cumulative Water Loss by the Plants in Group I

    Time (minutes)

    Average Cumulative Water Loss (milliliter H2O centimeter2)


    3.5 x 10-4


    7.7 x 10-4


    10.6 x 10-4

    1. Construct and label a graph using the data for Group I. Using the same set of axes, draw and label three additional lines representing the results that you would predict for Groups II, III, and IV.
    2. Explain how biological and physical processes are responsible for the difference between each of your predictions and the data for Group I.
    3. Explain how the concept of water potential is used to account for the movement of water from the plant stem to the atmosphere during transpiration.

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.

    Plant Seedling Mass (grams)
    Day 1Day 30
    Student A424
    Student B535
    Student C464
    1. Identify three different environmental variables that could account for differences in the mass of seedlings at day 30. Then choose one of these variables and design an experiment to test the hypothesis that your variable affects growth of these seedlings.
    2. Discuss the results you would expect if your hypothesis is correct. Then provide a physiological explanation for the effect of your variable on plant growth.

    Unit 15 (Ecology)

63.  Define and explain the role of each of the following in social behavior.

    1. Territoriality.
    2. Dominance hierarchies.
    3. Courtship 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.

    1. Pheromones.
    2. Mimicry.
    3. Stereotyped behavior (instinct).

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.

    1. Succession
    2. Energy flow between trophic levels.
    3. Limiting factors.
    4. Carrying capacity.

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 )

    1. Choosing organisms from four different trophic levels of this food web as examples, explain how energy is obtained at each trophic level.
    2. Describe the efficiency of energy transfer between trophic levels and discuss how the amount of energy available at each trophic level affects the structure of the ecosystem.
    3. If the cells in the dead terrestrial plant material that washed into the lake contained a commercially produced toxin, what would be the likely effects of this toxin on this food web? Explain.





    4 p.m.


    8 p.m.




For the data above, provide information on each of the following.

    • Summarize the pattern.
    • Identify THREE physiological or environmental variables that could cause the slugs to vary their distance from each other.
    • Explain how each variable could bring about the observed pattern of distribution.

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.

Cumulative Essays

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.

    1. C4 metabolism
    2. Amniotic egg
    3. Four-chambered heart
    4. Pollen

75.  Describe the anatomical and functional similarities and difference within each of the following pairs of structures.

    1. Artery—vein
    2. Small intestine—colon
    3. Skeletal muscle—cardiac muscle
    4. Anterior pituitary—posterior pituitary

76.  Discuss how each of the following has contributed to the evolutionary success of the organisms in which they are found.

    1. seeds
    2. mammalian placenta
    3. diploidy

77.  Angiosperms (flowering plants) and vertebrates obtain nutrients from their environment in different ways.

    1. Discuss the type of nutrition and the nutritional requirements of angiosperms and vertebrates.
    2. Describe 2 structural adaptations in angiosperms for obtaining nutrients from the environment. Relate structure to function.
    3. Interdependence in nature is evident in symbiosis. Explain tow symbiotic relationships that aid in nutrient uptake, using examples from angiosperms and/or vertebrates. (Both examples may be angiosperms, both may be vertebrates, or one may be from each group.

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.

    • The expression of a gene.
    • The activity of an enzyme.
    • The cell cycle.
    • The internal water balance of a plant.
    • The density of a population.

80.  Photosynthesis and cellular respiration recycle oxygen in ecosystems. Respond to TWO (and only two) of the following:

    1. Explain how the metabolic processes of cellular respiration and photosynthesis recycle oxygen.
    2. Discuss the structural adaptations that function in oxygen exchange between each of the following organisms and its environment: a plant; an insect; a fish.
    3. Trace a molecule of O2 from the environment to a muscle cell in a vertebrate of your choice.

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.

    1. Organisms recognize others as members of their own species.
    2. Neurotransmitters are recognized in the synapse.
    3. Antigens trigger antibody response.
    4. Nucleic acids are complementary.
    5. Target cells respond to specific hormones.

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.

  • communication between two plant cells
  • communication between two immune-system cells
  • communication either between a neuron and another neuron, or between a neuron and a muscle cell
  • communication between a specific endocrine-gland cell and its target cell


Reviewing for the AP Biology exam can seem daunting. There's so much material to cover, and much of it is highly complex. However, if you plan your time well and use appropriate study materials and strategies, you can expect a great score on the exam. In this article, I'll give you an overview of what the AP Biology exam is like, what you need to know to ace it, and how you can use your study time effectively before the exam on Monday, May 14, 2018 at 8 am! 


What’s the Format of the AP Biology Exam?

The AP Biology Exam is a long test, three hours long to be exact. Like other AP tests, it has two parts, a multiple-choice section and a free-response section (each of which is worth 50 percent of your score), although these sections are divided further into different types of questions.

The multiple choice section has 63 actual multiple-choice questions and six grid-in questions, which are essentially short-answer math problems. This section is one hour and 30 minutes total. Each multiple choice question has four choices, down from five in earlier versions of the exam. 

Even though you technically have more than a minute for each question, I would recommend keeping your time under a minute per multiple-choice question on your first pass through the section. You should also take into account the fact that the grid-in questions may be more time-consuming. There is no guessing penalty, so you should answer every question even if you have no idea which choice is correct (after you’ve tried to figure it out of course!).

The free-response section has eight questions total: six short-response questions and two long-response questions. This section takes up the remaining hour and thirty minutes of time. There is a 10 minute reading period at the beginning of the free response section. You’ll need to pace yourself wisely on this section as well. Try to spend no more than five minutes on each short free-response question. Even though they technically come after the long questions, I’d recommend doing the short questions first to get yourself warmed up. If you manage your time well, you’ll have at least 20-25 minutes left for each of the long free-response questions. 

Here's a chart showing the format of the exam.


Multiple-Choice Section

Free-Response Section


90 minutes

90 minutes

Number of Questions

63 multiple choice

6 grid-in

6 short response

2 long response

Percentage of Total Score





The AP Biology exam is a marathon, not a sprint. If it helps, during the test you can think about how lucky you are to be taking a test and not running an actual marathon.


What Do Questions Look Like on the AP Biology Exam?

Here’s an example of a multiple-choice question you might see on the AP Biology exam:

You don’t necessarily need lots of in-depth biology knowledge to answer this. The answer is A because the total volume of gas wouldn’t change (and oxygen consumption would be unmeasurable) unless the carbon dioxide produced by the organisms was removed from the environment. You can see this from the information contained in the question. This question is part of a group of three questions that pertain to the experiment and data chart. You’ll see many question clusters like this in the multiple-choice section.  


Here's an example of a grid-in question:

The grid-ins are usually straightforward math problems that relate to biological concepts (the answer to this question is 60). Note that you are allowed to use a calculator on the exam, and you’ll get a list of formulas that pertain to the course along with your testing materials.


Here’s an example of a short free-response question from the 2013 exam:

This question requires an understanding of how evolution shapes the formation of new species (one of the “Big Ideas” of AP biology, which I’ll talk about in the next section). To get the correct answer, you have to know the facts about evolution, but you also need to be able to apply that knowledge to make inferences about this specific scenario. This is why a deeper understanding of the main topics in AP Biology is so critical - the difference between knowing the facts about something and comprehending how it works can be surprisingly large. 


Here’s an example of a long free-response question:

This question is also heavier on analysis than straight up biology knowledge. You need to be able to read and understand the graphs and table so you can use them to inform your answer to the question. Once again, an understanding of evolution and the ability to apply that knowledge to a specific scenario is critical.

What Topics Does the AP Biology Exam Cover?

The College Board says in its Course Description that AP Biology has changed its focus from the more memorization-based curriculum that defined the course and exam in the past. The goal is for students to gain a deeper conceptual understanding of topics in biology. Reasoning skills and knowledge of the process of scientific inquiry are more important on the current AP Biology test than they have been before. 

The College Board has tried to structure the exam so that content knowledge and reasoning skills are intertwined. This can be both good and bad: the good is that you won’t necessarily have to memorize as many little tidbits of information, the bad is that it can be harder to study for a test like this that covers more abstract forms of knowledge. More on how to manage this in the “How to Review” section! 

The exam and curriculum as a whole will be centered around your understanding of these four “Big Ideas,” which each cover a bunch of different topics. Your success on the exam rests on being able to connect specific concepts with the overarching Big Ideas that define the course. 


Big Idea 1: The process of evolution drives the diversity and unity of life


  • Natural selection
  • Hardy-Weinberg
  • Biodiversity and categorization of organisms


Charles Darwin married his first cousin. You'd think he would know better.


Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis


  • Molecular biology
  • Biological systems and reactions
  • Photosynthesis
  • Cellular respiration
  • Cell structure
  • Cell membrane properties (diffusion and osmosis, proteins)
  • Thermodynamics/homeostasis
  • Immune response


Photosynthesis is way more elegant than eating. Then again, flowers will never taste ice cream, so I kinda feel sorry for them.


Big Idea 3: Living systems store, receive, transmit and respond to information essential to life processes


  • Genes and gene mutations
  • Cell cycle (mitosis, meiosis) and cell communication
  • Mendel and laws of inheritance
  • Viruses
  • Endocrine system
  • Nervous system


Deoxyribonucleic acid: It's DNAmazing!™


Big Idea 4: Biological systems interact, and these systems and their interactions possess complex properties


  • Enzymes
  • Plant structure and systems
  • Circulatory system
  • Digestive system
  • Musculoskeletal system
  • Ecological principles


Fun digestive system fact: If you eat a watermelon seed, a watermelon will grow inside your stomach. The ideal climate for watermelon growth is 96 degrees and highly acidic.


Apart from background knowledge of this content, it’s also important to understand your labs and the basic underlying principles that govern scientific experiments. If you know the ins and outs of experimental design, you’ll earn a lot of points on the exam. I recommend the CliffsNotes AP Biology 4th Edition review book as a helpful resource for going over labs, but you should also look back at what you did in your class. I'll provide more details on this in the next few sections.

Important Lab Topics Include:

  • Artificial Selection
  • Modeling Evolution
  • Comparing DNA Sequences
  • Diffusion and Osmosis
  • Photosynthesis
  • Cellular Respiration
  • Mitosis and Meiosis
  • Bacterial Transformation
  • Restriction Enzyme Analysis of DNA
  • Energy Dynamics
  • Transpiration
  • Animal Behavior
  • Enzyme Catalysis

Microscopes show us that the world around us is far creepier and grosser than we ever imagined.


AP Biology Review Preview: Important Tips to Keep in Mind

In this section, I'll give you some preliminary study tips that will help you get the most out of your AP Biology review time.   


Tip 1: Plan Out Your Time 

First of all, you should think about how much time you have left before the AP test. This will affect the structure of your study plan. If you're taking other AP classes or have a lot of commitments in general, you might want to start earlier depending on your confidence with the material. Consider your schedule and the time you're willing to spend on AP Biology. Since there's so much content in this course, I think 20 hours of studying is a reasonable goal. However, if you find that you're already scoring at a high level (a high 4 or anywhere in the 5 range), you might aim for just 10 hours or so. 

You should balance your time relatively evenly between studying the material and taking practice tests. In AP Biology, you might benefit from devoting a bit more time to practice testing. Since the test is now more targeted towards assessing analytical skills, practicing real AP questions may help you more than memorizing content (although both are still important!). I'll give you more information about how to use practice tests and review materials effectively in the next few sections. 


Tip 2: Use Appropriate Review Materials

The importance of using the right review materials can’t be overstated, especially in the case of AP Biology. With the recent changes to the test, it’s critical that you don’t use old study materials and assume they will give you all the tools you need to succeed in the new format. From reading student feedback on many AP Biology review books, it seems like some prep companies have struggled to adapt their practice questions and review methods to this version of the test. However, there are still resources out there that can help you. 

Review books that people found most useful include CliffsNotes AP Biology 5th Edition for content review and Sterling AP Biology Practice Questions for practice questions that will give you a good sense of what the new test is like. Pearson's Preparing for the AP Biology Exam book also has some good reviews and may be a nice source of practice free response questions.

Strangely enough, the most popular prep companies, like Princeton Review and Barron’s, have been less successful in updating their review materials to match the new test. If you get their review books, you should supplement them with practice questions from other sources. Avoid using practice questions that come from exams before the 2013 test, when the changes were implemented. You might still be able to use them to refresh your memory on certain topics, but they won’t really prepare you for the more analytical framework of questions on the current test.


Tip 3: Memorization Isn’t Enough

Even though AP Biology still involves a fair amount of memorization, you shouldn’t focus exclusively on content knowledge and assume you’ll do great on the test. Questions will test your critical thinking skills and logical reasoning abilities along with your knowledge of biology. That’s why it’s so important to spend a significant amount of time doing practice questions in addition to content review. Don’t let the test surprise you!


Tip 4: Don’t Forget About Labs

Revisiting old labs is not super fun (well, it wasn’t for me), so you might be tempted to ignore them and just focus on studying content outside of the lab context. Try to avoid this temptation! Go through your labs, and make sure you understand their methodologies and the reasoning behind the results. Understanding the scientific method and the components of a good experiment is absolutely key on the AP Bio exam. The more lab review you do, the more comfortable you'll feel during the test. 

Remember the lab where you melted down entire trees into a mysterious green serum? No? Well then, you better get studying!


How to Review for the AP Biology Exam

When you're studying for the exam, follow the five steps below to make sure your AP Bio review is as effective as possible.


Step 1: Take a Diagnostic Test

The first step of your AP Biology review is to take a practice exam so you can see how much you’ll need to study (and which areas need the most work). You should take your first complete practice test no later than the beginning of your second semester. You can use a practice exam from a review book or search online for a practice test. The review books I mentioned in the previous section have some good materials. 

When you take a practice test, make sure it’s the new version of the exam. If you see practice tests that have 100 multiple choice questions in the first section, you’re looking at an old version of the AP Biology Exam. You won’t be able to rely on your scores on this version to get a clear picture of where you fall on the new test.


Step 2: Calculate Your Score and Set a New Goal

Once you’ve taken a diagnostic test, you can calculate your score on the 1-5 AP scale. According to the CliffsNotes review book that I mentioned above, you can calculate your score using the following method:

  • Multiply the number of questions you answered correctly in section 1 (multiple choice and grid-in) by .725
  • Multiply the number of points you earned in section 2 by 1.25
  • Add those two numbers together to get your raw score

Then convert the raw score to an AP score:

Raw Composite Score

AP Score












For example, if you got 42 questions correct on the multiple choice/grid-in section and earned 25 points on the free response section, your raw score would be (42*.725) + (25*1.25) = 61.7 = just barely made it into the 5 category! This is without taking the curve into account, which is different every year, but it should give you a rough idea of where you stand. Unless you’re scoring a really high 5 (90+), you should still put in a bit of study time to make sure you’re fully prepared.

If you score low (a 1 or a 2), you might make it your goal to raise your score to a 3. Just keep in mind that some schools don't accept 3s for college credit, so you may want to aim higher after you make it to this first milestone. Most colleges consider a 4 to be the standard cutoff for AP credit, so you should try for at least a 4 if you're hoping to get a head start in college. Once you're consistently scoring in the 3 range, you can set a 4 or 5 as your goal.

Even if you’re already at the 4 or 5 level, you probably still have some room to improve. It’s nice to get in some extra practice so that you feel very comfortable on the real test. Depending on how much you need to improve and how long you want to spread out your studying, you might come up with different plans. To improve by one AP score point, you can get away with studying only two months or so in advance. If you’re hoping to improve by 2 or more AP score points, you should try to start midway through the school year if you want to avoid cramming.


Confidence is key. If you need to wear a business suit to the test to make yourself feel in control, go for it (I am not responsible for the relentless mocking you will endure from your peers). 


Step 3: Analyze Your Mistakes

This is the most critical part of the review process, and it’s particularly important for AP Biology. There’s a lot of material to learn, and you don’t want to waste time going over concepts that you already have down. Comb through your mistakes on the diagnostic test to see where the most errors happened and why. Did your problems center more around lack of knowledge of background information or difficulty analyzing the scenarios presented to you on the test (you knew the information, but you couldn’t get the question because it confused you)? 

You will most likely have a little of each type of problem, but if one is more prevalent than the other, you should take that into account for your studying strategy. For example, it wouldn’t be a good idea to keep drilling yourself on basic content knowledge if most of your mistakes came in the form of misinterpreting complex questions or reading diagrams incorrectly. You would want to devote less of your time to reviewing biological terms and more of your time to doing real practice questions. 

Even in those cases, you’ll probably still have at least a few issues with content knowledge. As you go through your mistakes, keep a running list of the ideas you need to revisit in your notes or review book. If you’re caught off guard by your unfamiliarity with a certain topic, you should pay special attention to that topic in your studying. You may also notice mistakes due to carelessness or time pressure that aren’t directly related to your knowledge of the material or understanding of the question. In this case, you'll need to think about revising your basic test-taking strategies. In the next step, I’ll go into more detail on this.


Do some practice test detective work! I think this is a detective. Either that or a random guy smoking a pipe and trying to figure out how bad the pimple on his nose looks.


Step 4: Fix Your Mistakes

There are a few things you can do to revise your strategies for taking the exam and effectively review concepts that you didn’t understand. The obvious first step is to go back into your textbook, your notes, or a reliable review book (or even all three!) and brush up on the information you forgot. Sometimes for biology, this is a little overwhelming because of the complexity of the material.

If you’re trying to understand systems or processes, I’d recommend testing yourself by drawing diagrams of how they work. This will allow you to make connections between dry facts presented in the text and the biological reality of what’s happening in the system. It will help you not only in your content knowledge but also in your ability to analyze related scenarios on the test. You can use this strategy for many concepts in AP Biology, and it will make them much simpler to understand. 

To correct your other mistakes that have more to do with question comprehension, you'll need to focus on doing similar practice questions. I’d recommend getting this book of Sterling AP Biology Practice Questions for some questions that are organized logically by topic area and well-aligned with the new exam format. More practice is also a good remedy for careless errors and time management problems. You can learn how to better identify the key parts of each question and avoid distractions that might throw you off.

Underlining the most important parts of the question can be a good strategy if you’re prone to careless errors. If time management is a problem, put some thought into why you ran out of time. Did you linger for too long on difficult questions? Remember, it’s a smart idea to skip questions that are giving you a lot of trouble (not answerable within a minute) and come back to them later once you’ve gotten through the whole section. 


Practice makes perfect. Maybe you can compose an AP Biology song to help you remember stuff. "Now enzymes....BREAK IT DOWN!" 

Step 5: Take Another Test and Repeat Previous Steps

Now that you’ve analyzed and fixed your mistakes on the diagnostic test and done some more targeted studying, it’s time to take another practice test. Score the new test, then repeat steps 3 and 4. You should notice improvements as you continue to repeat this process and gain familiarity with the format and content of the test.

If you don’t notice positive changes from one test to the next, it may be time to reevaluate your review techniques. Depending on how early you start studying and how much you want to improve, you might go through these steps once, twice, or seven times. You can continue the process until you achieve your score goals or run out of study time!  



The AP Biology test is a long exam, and it covers a wide range of material. Recently, the test was updated to focus less on information recall and more on analytical thinking, which can be good and bad. You won't have to rely on memorization as much, but your score will be highly dependent on your ability to think through complicated scenarios that are presented on the test.

In your AP Biology review, you should still go over all of the information you learned in the course. However, you should also devote a significant amount of your time to practice testing so that you can learn to think the way the test wants you to think. If you plan your study time wisely and learn how to solve the types of questions that are most difficult for you, you'll be on your way to a great score!


What's Next?

Wondering exactly how much time you have before your AP tests? Here are the AP test dates and times for 2018.

If you're in AP Biology, you may think about taking the Biology SAT Subject Test as well. Find out the difference between AP tests and SAT Subject Tests and which are more important for college. 

Considering an AP Calculus course? Read this article for some guidance on deciding whether you should take AP Calculus AB or BC.


Want to improve your SAT score by 160 points or your ACT score by 4 points? We've written a guide for each test about the top 5 strategies you must be using to have a shot at improving your score. Download it for free now:


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