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2021 CLEP Official Study Guide

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This study guide provides practice questions for all 34 CLEP exams. The ideal resource for taking more than one exam. Offered only by the College Board.

CLEP® Biology Examination Guide

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The Biology exam covers molecular and cellular biology, organismal biology, and population biology.

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The Biology examination covers material that is usually taught in a one-year college general biology course. The subject matter tested covers the broad field of the biological sciences, organized into three major areas: molecular and cellular biology, organismal biology, and population biology.

The examination gives approximately equal weight to these three areas. The examination contains approximately 115 questions to be answered in 90 minutes. Some of these are pretest questions that will not be scored. Any time candidates spend on tutorials and providing personal information is in addition to the actual testing time.

Knowledge and Skills Required

Questions on the Biology exam require test takers to demonstrate one or more of the following abilities.

  • Knowledge of facts, principles, and processes of biology
  • Understanding the means by which information is collected, how it is interpreted, how one hypothesizes from available information, and how one draws conclusions and makes further predictions
  • Understanding that science is a human endeavor with social consequences

The subject matter of the Biology exam is drawn from the following topics. The percentages next to the main topics indicate the approximate percentage of exam questions on that topic.

Molecular and Cellular Biology (33%)

Chemical composition of organisms

  • Simple chemical reactions and bonds
  • Properties of water
  • Chemical structure of carbohydrates, lipids, proteins, nucleic acids
  • Origin of life


  • Structure and function of cell organelles
  • Properties of cell membranes
  • Comparison of prokaryotic and eukaryotic cells


  • Enzyme-substrate complex
  • Roles of coenzymes
  • Inorganic cofactors
  • Inhibition and regulation

Energy transformations

  • Glycolysis, respiration, anaerobic pathways
  • Photosynthesis

Cell division

  • Structure of chromosomes
  • Mitosis, meiosis, and cytokinesis in plants and animals

Chemical nature of the gene

  • Watson-Crick model of nucleic acids
  • DNA replication
  • Mutations
  • Control of protein synthesis: transcription, translation, posttranscriptional processing
  • Structural and regulatory genes
  • Transformation
  • Viruses

Organismal Biology (34%)

Structure and function in plants with emphasis on angiosperms

  • Root, stem, leaf, flower, seed, fruit
  • Water and mineral absorption and transport
  • Food translocation and storage

Plant reproduction and development

  • Alternation of generations in ferns, conifers, and flowering plants
  • Gamete formation and fertilization
  • Growth and development: hormonal control
  • Tropisms and photoperiodicity

Structure and function in animals with emphasis on vertebrates

  • Major systems (e.g., digestive, gas exchange, skeletal, nervous, circulatory, excretory, immune)
  • Homeostatic mechanisms
  • Hormonal control in homeostasis and reproduction

Animal reproduction and development

  • Gamete formation, fertilization
  • Cleavage, gastrulation, germ layer formation, differentiation of organ systems
  • Experimental analysis of vertebrate development
  • Extraembryonic membranes of vertebrates
  • Formation and function of the mammalian placenta
  • Blood circulation in the human embryo

Principles of heredity

  • Mendelian inheritance (dominance, segregation, independent assortment)
  • Chromosomal basis of inheritance
  • Linkage, including sex-linked
  • Polygenic inheritance (height, skin color)
  • Multiple alleles (human blood groups)

Population Biology (33%)

Principles of ecology

  • Energy flow and productivity in ecosystems
  • Biogeochemical cycles
  • Population growth and regulation (natality, mortality, competition, migration, density, r- and K-selection)
  • Community structure, growth, regulation (major biomes and succession)
  • Habitat (biotic and abiotic factors)
  • Concept of niche
  • Island biogeography
  • Evolutionary ecology (life history strategies, altruism, kin selection)

Principles of evolution

  • History of evolutionary concepts
  • Concepts of natural selection (differential reproduction, mutation, Hardy-Weinberg equilibrium, speciation, punctuated equilibrium)
  • Adaptive radiation
  • Major features of plant and animal evolution
  • Concepts of homology and analogy
  • Convergence, extinction, balanced polymorphism, genetic drift
  • Classification of living organisms
  • Evolutionary history of humans

Principles of behavior

  • Stereotyped, learned social behavior
  • Societies (insects, birds, primates)

Social biology

  • Human population growth (age composition, birth and fertility rates, theory of demographic transition)
  • Human intervention in the natural world (management of resources, environmental pollution)
  • Biomedical progress (control of human reproduction, genetic engineering)

Study Resources

Most textbooks used in college-level biology courses cover the topics in the outline given earlier, but the approaches to certain topics and the emphases given to them may differ. To prepare for the Biology exam, it is advisable to study one or more college textbooks, which can be found in most college bookstores. When selecting a textbook, check the table of contents against the knowledge and skills required for this test. Candidates would do well to consult pertinent articles from magazines such as Scientific American, Science News, and Natural History.


A survey conducted by CLEP found that the following textbooks are among those used by college faculty who teach the equivalent course. You might purchase one or more of these online or at your local college bookstore.

  • Audesirk, Audesirk, and Byers, Biology: Life on Earth (Benjamin Cummings)
  • Brooker, Widmaier, Graham, and Stiling, Biology (McGraw-Hill)
  • Cain, et. al., Discover Biology (W.W. Norton)
  • Campbell and Reece, Biology (Benjamin Cummings)
  • Campbell, Reece, Taylor, and Simon, Biology: Concepts and Connections (Benjamin Cummings)
  • Enger et al., Concepts in Biology (McGraw-Hill)
  • Freeman, Biological Science (Benjamin Cummings)
  • Lewis et al., Life (McGraw-Hill)
  • Mader, Essentials of Biology (McGraw-Hill)
  • Sadava, et al., Life: The Science of Biology (W.H. Freeman)
  • Solomon et al., Biology (Brooks/Cole)
  • Raven et al., Biology (McGraw-Hill)
  • Russell, Wolfe, Hertz, and Starr, Biology: The Dynamic Science (Brooks/Cole; Thomson Learning)
  • Starr, Biology: Concepts and Applications (Brooks/Cole)
  • Tobin and Dusheck, Asking About Life (Brooks/Cole)

Online Resources

These resources, compiled by the CLEP test development committee and staff members, may help you study for your exam. However, none of these sources are designed specifically to provide preparation for a CLEP exam. The College Board has no control over their content and cannot vouch for accuracy.

Score Information

Credit-Granting Score for Biology

ACE Recommended Score*: 50
Semester Hours: 6

Each institution reserves the right to set its own credit-granting policy, which may differ from that of ACE. Contact your college as soon as possible to find out the score it requires to grant credit, the number of credit hours granted, and the course(s) that can be bypassed with a satisfactory score.

*The American Council on Education’s College Credit Recommendation Service (ACE CREDIT) has evaluated CLEP processes and procedures for developing, administering, and scoring the exams. The score listed above is equivalent to a grade of C in the corresponding course. The American Council on Education, the major coordinating body for all the nation’s higher education institutions, seeks to provide leadership and a unifying voice on key higher education issues and to influence public policy through advocacy, research, and program initiatives. Visit the ACE CREDIT website for more information.