Free CLEP Biology Practice Questions

Sample Practice Questions

Try these 10 sample questions from the CLEP Biology practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1What holds the atoms together in a covalent bond?

   1. A.Attraction between oppositely charged ions
   2. B.Sharing a pair of electrons between atomsCorrect answer: B
   3. C.Attraction between partial charges on molecules
   4. D.Sharing delocalized electrons in a metal lattice

   Explanation: "Another way to satisfy the octet rule is by sharing electrons between atoms to form covalent bonds." A covalent bond involves sharing electrons; attraction between ions describes ionic bonding.

   Reference: Biology 2e, Atoms, Isotopes, Ions, and Molecules — Covalent Bonds and Other Bonds and Interactions

2. 2Which plant tissue conducts water and dissolved minerals from roots toward leaves?

   1. A.Phloem
   2. B.XylemCorrect answer: B
   3. C.Epidermis
   4. D.Palisade mesophyll

   Explanation: "Xylem tissue transports water and nutrients from the roots to different parts of the plant, and includes three different cell types: vessel elements and tracheids (both of which conduct water), and xylem parenchyma." Xylem conducts water and minerals; phloem carries photosynthates.

   Reference: Biology 2e, The Plant Body — Plant Tissue Systems

3. 3In an ecosystem, what does net primary productivity measure?

   1. A.Energy retained by primary producers after respiration and heat lossCorrect answer: A
   2. B.Total energy absorbed before producers respire
   3. C.Energy released by consumers through respiration
   4. D.All sunlight reaching an ecosystem's surface

   Explanation: "Net primary productivity is the energy that remains in the primary producers after accounting for the organisms’ respiration and heat loss." Net primary productivity excludes energy used in producer respiration.

   Reference: Biology 2e, Energy Flow through Ecosystems — Productivity within Trophic Levels

4. 4What property of electron sharing makes a covalent bond polar?

   1. A.Electrons are transferred completely between atoms.
   2. B.Electrons are shared equally between the atoms.
   3. C.Electrons are shared unequally between the atoms.Correct answer: C
   4. D.Electrons are delocalized across a metal lattice.

   Explanation: "In a polar covalent bond, Figure 2.12 shows atoms unequally share the electrons as the electrons are attracted more to one nucleus than the other." Unequal electron sharing creates partial charges; equal sharing does not.

   Reference: Biology 2e, Atoms, Isotopes, Ions, and Molecules — Polar Covalent Bonds

5. 5How do root hairs increase a plant's uptake of water and minerals?

   1. A.They increase the surface area exposed to soil.Correct answer: A
   2. B.They decrease the surface area exposed to soil.
   3. C.They replace the root's water-conducting xylem.
   4. D.They block water movement across the epidermis.

   Explanation: "Root hairs, which are extensions of root epidermal cells, increase the surface area of the root, greatly contributing to the absorption of water and minerals." Their increased surface area promotes absorption from the soil.

   Reference: Biology 2e, Roots — Root Anatomy

6. 6Why is less energy typically available at successive trophic levels?

   1. A.Some energy is released as metabolic heat at each transfer.Correct answer: A
   2. B.Most energy becomes new consumer biomass at each transfer.
   3. C.Energy cycles unchanged between successive trophic levels.
   4. D.Predators obtain more energy than their food contains.

   Explanation: "In biologic systems, this energy takes the form of metabolic heat, which is lost when the organisms consume other organisms." Metabolism dissipates part of the energy as heat, limiting transfer.

   Reference: Biology 2e, Energy Flow through Ecosystems — Ecological Efficiency: The Transfer of Energy between Trophic Levels

7. 7When sodium chloride dissolves in water, which part of a water molecule faces a sodium ion in its hydration shell?

   1. A.The partially positive hydrogen side
   2. B.The partially negative oxygen sideCorrect answer: B
   3. C.Either side with no charge preference
   4. D.The oxygen side after gaining a full negative charge

   Explanation: "The partially negative charge of the water molecule’s oxygen surrounds the positively charged sodium ion." Opposite partial and ionic charges attract in the hydration shell.

   Reference: Biology 2e, Water — Water’s Solvent Properties

8. 8Which cells control the opening and closing of a leaf stoma?

   1. A.Tracheids
   2. B.Sieve elements
   3. C.Guard cellsCorrect answer: C
   4. D.Palisade cells

   Explanation: "Two guard cells surround each stoma, regulating its opening and closing." Guard cells regulate the pore; the other cells have different roles.

   Reference: Biology 2e, Leaves — Leaf Structure and Function

9. 9In the carbon cycle, which process incorporates atmospheric carbon dioxide into organic carbon?

   1. A.PhotosynthesisCorrect answer: A
   2. B.Aerobic respiration
   3. C.Combustion of fossil fuels
   4. D.Decomposition

   Explanation: "Photosynthesis converts carbon dioxide gas to organic carbon, and respiration cycles the organic carbon back into carbon dioxide gas." Photosynthesis fixes carbon dioxide into organic matter.

   Reference: Biology 2e, Biogeochemical Cycles — Section 46.3, The Carbon Cycle, Figure 46.15

10. 10Which water property helps a body resist rapid temperature changes when it absorbs heat?

    1. A.Its high specific heat capacityCorrect answer: A
    2. B.Its low heat of vaporization
    3. C.Its low capacity for adhesion
    4. D.Its high rate of dissociation

    Explanation: "We define specific heat as the amount of heat one gram of a substance must absorb or lose to change its temperature by one degree Celsius." A high specific heat means more energy is needed for a given temperature increase.

    Reference: Biology 2e, Water — Water’s High Heat Capacity