Free Praxis Biology (5236) Practice Questions

Sample Practice Questions

Try these 10 sample questions from the Praxis Biology (5236) practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1Which feature makes an explanation of a biological phenomenon a scientifically testable hypothesis?

   1. A.It predicts observations that could show it is incorrect.Correct answer: A
   2. B.It describes an event that cannot be observed indirectly.
   3. C.It has been accepted by a majority of the students.
   4. D.It avoids making predictions about measurable outcomes.

   Explanation: The text states, "A valid hypothesis must be testable. It should also be falsifiable, meaning that experimental results can disprove it." A hypothesis must expose its explanation to a possible contradictory observation; popularity does not provide that test.

   Reference: Biology 2e — The Science of Biology — 1.1, Testing a Hypothesis

2. 2How does the hydrogen ion concentration of a solution at pH 3 compare with that of a solution at pH 5?

   1. A.It is 2 times as high.
   2. B.It is 100 times as high.Correct answer: B
   3. C.It is 2 times as low.
   4. D.It is 100 times as low.

   Explanation: OpenStax describes pH as "the negative of the base 10 logarithm". A decrease of two pH units corresponds to 10² = 100 times the hydrogen ion concentration.

   Reference: Biology 2e — Water — 2.2, pH, Buffers, Acids, and Bases

3. 3A DNA strand has the sequence 3′-ACGT-5′. Which sequence is its complementary DNA strand, written antiparallel?

   1. A.5′-ACGT-3′
   2. B.5′-UGCA-3′
   3. C.5′-AGCT-3′
   4. D.5′-TGCA-3′Correct answer: D

   Explanation: NHGRI states, "adenine bonds with thymine, and cytosine bonds with guanine". Applying these pairing rules at each position gives the antiparallel sequence TGCA.

   Reference: NHGRI — Deoxyribonucleic Acid (DNA) — Definition

4. 4Which taxonomic rank is immediately more inclusive than genus in the standard hierarchy?

   1. A.Species
   2. B.Order
   3. C.Class
   4. D.FamilyCorrect answer: D

   Explanation: OpenStax lists the sequence "order, family, genus, and species". Family groups related genera and is directly above genus.

   Reference: Biology 2e — Organizing Life on Earth — 20.1, Classification Levels

5. 5A survey includes all populations of fish, aquatic plants, insects, and microorganisms living in a pond. Which ecological level is represented by these living populations together?

   1. A.One population
   2. B.A biosphere
   3. C.A communityCorrect answer: C
   4. D.One organism

   Explanation: OpenStax states, "All populations occupying the same habitat form a community". The survey includes multiple species rather than one population.

   Reference: Biology 2e — Community Ecology — 45.6, introductory definition

6. 6Students test whether a fertilizer increases seedling growth. They randomly assign similar seedlings to two groups and keep light, water, soil, and temperature alike. Which treatment provides the appropriate control group?

   1. A.Seedlings given twice the fertilizer dose
   2. B.Seedlings grown with a different soil type
   3. C.Seedlings given water without the fertilizerCorrect answer: C
   4. D.Seedlings measured only before treatment

   Explanation: The source explains, "The control group contains every feature of the experimental group except it is not given the manipulation that the researcher hypothesizes." With other conditions matched, withholding fertilizer creates the comparison needed to evaluate its effect.

   Reference: Biology 2e — The Science of Biology — 1.1, Testing a Hypothesis

7. 7A small amount of acid is added to a buffered solution. Which response helps limit the resulting decrease in pH?

   1. A.The buffer releases hydrogen ions as their free concentration rises.
   2. B.The buffer binds hydroxide ions rather than the added hydrogen ions.
   3. C.The buffer binds some of the added hydrogen ions.Correct answer: C
   4. D.The buffer shifts toward a higher conjugate-base to weak-acid ratio.

   Explanation: OpenStax states, "Buffers readily absorb excess H+ or OH–". Binding added hydrogen ions limits their increase in free concentration and therefore moderates the pH change.

   Reference: Biology 2e — Water — 2.2, pH, Buffers, Acids, and Bases

8. 8Which repeating components form the backbone of a DNA strand?

   1. A.Amino acids and peptide groups
   2. B.Deoxyribose sugars and phosphate groupsCorrect answer: B
   3. C.Ribose sugars and amino groups
   4. D.Nitrogenous bases and fatty acids

   Explanation: NHGRI describes a backbone of "alternating sugar (deoxyribose) and phosphate groups". Bases attach to the sugars but do not form this repeating backbone.

   Reference: NHGRI — Deoxyribonucleic Acid (DNA) — Definition

9. 9In the scientific name Panthera leo, what does Panthera identify?

   1. A.The family
   2. B.The genusCorrect answer: B
   3. C.The order
   4. D.The domain

   Explanation: OpenStax describes binomial names using "genus and species". The first word identifies the genus, while the second is the specific epithet.

   Reference: Biology 2e — Organizing Life on Earth — 20.1, Classification Levels, binomial nomenclature

10. 10Which study addresses an ecosystem rather than only its biological community?

    1. A.A study of pond organisms together with nutrient concentrations, light, and water chemistryCorrect answer: A
    2. B.A count of all fish species inhabiting the pond
    3. C.An inventory of feeding relationships among pond animals
    4. D.A comparison of the pond's plant populations

    Explanation: OpenStax includes the "abiotic, nonliving parts" in an ecosystem. Light and water chemistry add nonliving environmental components to the community.

    Reference: Biology 2e — Themes and Concepts of Biology — 1.2, Levels of Organization of Living Things, ecosystem