Free CLEP Natural Sciences Practice Questions

Sample Practice Questions

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

1. 1In population genetics, which change in a population constitutes evolution?

   1. A.A change in the frequency of an allele in a population over generationsCorrect answer: A
   2. B.A change in an individual's body size during its lifetime
   3. C.A seasonal change in the food available to a population
   4. D.A temporary change in an individual's behavior

   Explanation: OpenStax states, "In population genetic terms, evolution is defined as a change in the frequency of an allele in a population." Changes in individuals or their environment do not by themselves establish a population-level allele-frequency change.

   Reference: Concepts of Biology, 11.1 Discovering How Populations Change — Population Genetics

2. 2Atoms of two isotopes of the same element differ in which quantity?

   1. A.The number of protons in the nucleus
   2. B.The number of neutrons in the nucleusCorrect answer: B
   3. C.The atomic number of the nucleus
   4. D.The positive charge of each proton

   Explanation: The source states, "isotopes of an element, therefore, differ from each other only in the number of neutrons within the nucleus." Their proton numbers, and hence atomic numbers, are the same.

   Reference: Chemistry 2e, Chapter 2 Summary — Chapter 2 summary, atomic structure

3. 3For natural selection to produce a change in a population across generations, what must be true of the relevant variation among individuals?

   1. A.It must be caused entirely by differences in nutrition.
   2. B.It must have a genetic basis that can be inherited.Correct answer: B
   3. C.It must occur equally in every individual in the population.
   4. D.It must be acquired during each individual's lifetime.

   Explanation: OpenStax explains, "these differences must have some genetic basis; otherwise, selection will not lead to change in the next generation." Environmental differences alone need not be inherited, and identical individuals do not provide the variation selection requires.

   Reference: Concepts of Biology, 11.1 Discovering How Populations Change — Variation and Adaptation

4. 4A neutral atom has 12 protons. How many electrons does it have?

   1. A.6
   2. B.12Correct answer: B
   3. C.24
   4. D.11

   Explanation: The source states, "An atom is neutral when it contains equal numbers of electrons and protons." Twelve protons therefore require twelve electrons in a neutral atom.

   Reference: Chemistry 2e, Chapter 2 Summary — Chapter 2 summary, atomic structure

5. 5What is the ultimate source of new alleles in a population?

   1. A.Natural selection of existing traits
   2. B.Crossing over between existing chromosomes
   3. C.Mutation producing changes in DNACorrect answer: C
   4. D.Recombination of existing parental alleles

   Explanation: The text states, "Mutation, a change in DNA, is the ultimate source of new alleles or new genetic variation in any population." Recombination and crossing over form new combinations of alleles; selection changes the representation of inherited variants.

   Reference: Concepts of Biology, 11.1 Discovering How Populations Change — Variation and Adaptation

6. 6A nucleus contains 8 protons and 10 neutrons. What is its mass number?

   1. A.8
   2. B.10
   3. C.18Correct answer: C
   4. D.20

   Explanation: The source states, "The sum of the numbers of protons and neutrons in the nucleus is called the mass number". Adding 8 and 10 gives 18.

   Reference: Chemistry 2e, Chapter 2 Summary — Chapter 2 summary, atomic structure

7. 7What does a branch point in a phylogenetic tree represent?

   1. A.The point at which all evolution in a lineage stops
   2. B.The point at which two living species become identical
   3. C.The point at which unrelated lineages merge into one
   4. D.The point at which one lineage splits into distinct lineagesCorrect answer: D

   Explanation: The text states, "The point where a split occurs in a tree, called a branch point, represents where a single lineage evolved into distinct new ones." It represents divergence, not the merger or termination of lineages.

   Reference: Concepts of Biology, 12.1 Organizing Life on Earth — Classification and Phylogeny

8. 8What is an alpha particle emitted during nuclear decay?

   1. A.A high-energy helium nucleusCorrect answer: A
   2. B.A high-energy electron
   3. C.A photon of electromagnetic radiation
   4. D.A single neutron

   Explanation: The source identifies "alpha (α) particles (which are high-energy helium nuclei)". It identifies beta particles as electrons and gamma rays as electromagnetic radiation.

   Reference: Chemistry 2e, Chapter 21 Summary — Chapter 21 summary, Nuclear Equations

9. 9In binomial nomenclature, which two taxonomic names are used together to identify an organism?

   1. A.Its domain and kingdom names
   2. B.Its family and order names
   3. C.Its genus and species namesCorrect answer: C
   4. D.Its phylum and class names

   Explanation: OpenStax states, "Scientists refer to an organism by its genus and species names together, commonly called a scientific name, or Latin name." The other pairs are taxonomic ranks but are not the two parts of a binomial name.

   Reference: Concepts of Biology, 12.1 Organizing Life on Earth — The Levels of Classification

10. 10A radioactive sample initially contains 80 mg of an isotope. How much of that isotope remains after two half-lives?

    1. A.10 mg
    2. B.20 mgCorrect answer: B
    3. C.40 mg
    4. D.60 mg

    Explanation: The source defines half-life as "the time that is required for half of its atoms to decay." Half of 80 mg remains after one half-life, and half of that 40 mg remains after the second, giving 20 mg.

    Reference: Chemistry 2e, Chapter 21 Summary — Chapter 21 summary, Radioactive Decay