CLEP Practice Test Biology

Question 1

Farm runoff washes fertilizer into a pond, causing increased algal growth, decreased oxygen, and eventually the death of the fish. Which of the following processes best describes this sequence of events?

Accepted Answer

Eutrophication

Answer

Eutrophication is the process where a body of water becomes overly enriched with nutrients, typically from agricultural runoff containing fertilizers. This excess nutrient load stimulates an explosive growth of algae (algal bloom). When these algae die and decompose, bacteria consume large amounts of dissolved oxygen, leading to hypoxia or anoxia, which ultimately causes the death of aquatic life like fish.

Question 2

Dogs, bats, whales, and humans all have a long bone in their front limbs that is attached to two parallel bones at a joint. Anatomical structures such as these are referred to as

Accepted Answer

Homologous

Answer

Homologous structures are anatomical similarities between different species that indicate a shared ancestry, even if the structures now serve different functions. The forelimbs of dogs, bats, whales, and humans, despite their varied uses (walking, flying, swimming, grasping), share a fundamental underlying bone structure (humerus, radius, ulna), which is a classic example of homology and evidence for common descent.

Question 3

Why is it likely that a single nucleotide substitution of uracil for thymine in a DNA strand's coding region will have little effect on the organism?

I. Uracil and thymine nucleotides will both bind to adenosine
II. The genetic code is duplicative
III. Single nucleotide substitutions rarely have a significant impact
IV. Because uracil is not normally found in DNA, the substitution is likely to be detected and repaired.

Accepted Answer

I and IV

Answer

A single nucleotide substitution of uracil for thymine in DNA is unlikely to have a significant effect for two main reasons. First, both uracil and thymine nucleotides bind to adenosine, meaning the base pairing rules are maintained during replication and transcription, thus preserving the original genetic information and resulting in the same mRNA codon. Second, uracil is not a normal component of DNA, and specialized DNA repair enzymes are present in cells to detect and remove uracil, replacing it with thymine, thereby preventing the persistence of this unusual base.

Question 4

In humans, what is the end result of anaerobic respiration?

Accepted Answer

Lactic acid

Answer

In humans, when oxygen is scarce, such as during intense exercise, cells switch from aerobic respiration to anaerobic respiration to produce ATP. This process, known as lactic acid fermentation, breaks down glucose without oxygen, yielding a small amount of ATP and producing lactic acid as a byproduct. The accumulation of lactic acid contributes to muscle fatigue and soreness.

Question 5

Chyme is a semi-fluid mass of partially digested food. Chyme formation takes place in

Accepted Answer

Stomach

Answer

Chyme is the semi-fluid, acidic mass of partially digested food that is formed in the stomach. After food is chewed and swallowed, it enters the stomach where it is mixed with gastric juices (containing hydrochloric acid and enzymes like pepsin) and churned by muscular contractions, transforming it into chyme before it passes into the small intestine.