Free CLEP Biology Practice Test (2026)

In what form is most of the carbon dioxide carried in human blood from the tissues to the lungs?

A population of 1,000 plants is in Hardy-Weinberg equilibrium for one gene, and 90 plants show the recessive phenotype (aa). How many plants are expected to be heterozygous (Aa)?

In a moss, the familiar green, leafy plant is haploid. Which statement about the moss life cycle is correct?

At a chemical synapse, what happens immediately after an action potential reaches the axon terminal?

In a human fetus, the foramen ovale (an opening between the right and left atria) and the ductus arteriosus send most of the blood around which organ?

Two genes lie on the same chromosome. A test cross of an organism heterozygous for both genes gives offspring in these proportions: 42% AB, 42% ab, 8% Ab and 8% aB. How far apart are the genes on a genetic map?

A plant cell has a diploid number of 12 (2n = 12). At the end of meiosis I, before meiosis II begins, how many chromosomes and chromatids does each new cell have?

Two closely related frog species live in the same pond. One breeds in early spring and the other in late spring, so they never interbreed. This is an example of

Nitrate fertilizer spread on a waterlogged, oxygen-poor field is gradually lost to the air as nitrogen gas. Which process is responsible?

On a rocky shore, barnacle species X lives only in the upper intertidal zone. When a researcher removes species Y from the lower zone, species X spreads down into it. What does the upper zone represent for species X?

Intestinal cells take in glucose against its concentration gradient by moving it together with sodium ions, which flow into the cell down their own gradient. A sodium-potassium pump that uses ATP keeps the sodium gradient in place. How is the glucose transported?

During DNA replication, why is the lagging strand built as a series of short fragments?

Yeast cells kept without oxygen convert pyruvate to ethanol and carbon dioxide. This step makes no ATP. What is its main benefit to the cell?

Which change near the start of a gene's coding sequence is most likely to produce a completely nonfunctional protein?

The seeds of a mutant corn plant sprout while still on the cob instead of staying dormant. A shortage of which plant hormone would most likely cause this?

A population grows according to the logistic model with carrying capacity K. At what population size is the number of individuals added per year greatest?

When blood calcium falls, the parathyroid glands release parathyroid hormone (PTH). Which response follows?

Hemophilia A is an X-linked recessive disorder. A man with hemophilia and a woman with two normal alleles have children. Which outcome is expected?

In the 1950s, Stanley Miller and Harold Urey passed electric sparks through a mixture of gases then thought to resemble Earth's early atmosphere: methane, ammonia, hydrogen and water vapor. What did the experiment show?

A honeybee scout returns to the hive and performs a waggle dance on the vertical comb. What does the angle of the waggle run, measured from straight up, tell other bees?

A country's population pyramid has a very wide base that narrows steadily toward the top. What does this shape most likely indicate?

What mainly moves water to the top leaves of a 60-meter-tall tree?

Hunting reduced a seal population to about 20 animals. The population has since recovered to more than 30,000, but its genetic diversity is very low. Which process best explains the low diversity?

A plant is given water made with the heavy oxygen isotope ¹⁸O, along with ordinary CO₂, and is placed in light. Where will the ¹⁸O first show up?

An enzyme inhibitor slows a reaction, but its effect almost disappears when the substrate concentration is made very high. What does this suggest about the inhibitor?