WCAS - Washington Comprehensive Assessment of Science Heredity and Biological Evolution Questions and Answers

Question 1

The forelimbs of a human, the wing of a bat, and the flipper of a whale all have a very similar bone structure, despite performing different functions. Which of the following is the BEST explanation for this observation?

Accepted Answer

These organisms share a common ancestor that had a similar forelimb structure.

Answer

This is an example of homologous structures. These are structures that are similar in related organisms because they were inherited from a common ancestor. Even though the forelimbs are used for different functions (grasping, flying, swimming), the underlying similarity in bone arrangement points to a shared evolutionary history.

Question 2

In a population of rock pocket mice, most individuals have light-colored fur, which provides camouflage on sandy soil. A volcanic eruption covers the area in dark lava rock. Over many generations, the frequency of mice with dark-colored fur increases significantly in the population. This scenario is an example of:

Accepted Answer

Natural selection

Answer

This is a classic example of natural selection. The change in environment (dark lava rock) made dark-colored fur an advantageous trait for survival, as it provided better camouflage from predators. Mice with this heritable trait were more likely to survive and reproduce, passing the trait to their offspring, which led to an increase in its frequency in the population over time.

Question 3

Which of the following statements BEST describes the primary role of genetic mutation in the process of evolution?

Accepted Answer

Mutations are the ultimate source of new genetic variation in a population.

Answer

Mutations are random changes in an organism's DNA sequence that introduce new alleles and traits into a population's gene pool. This genetic variation is the raw material upon which natural selection can act. While mutations can be harmful or neutral, they can also be beneficial, providing the foundation for evolutionary change.

Question 4

Which statement accurately describes the relationship between genes, chromosomes, and DNA?

Accepted Answer

Genes are segments of DNA, which is tightly coiled to form chromosomes.

Answer

The correct hierarchical relationship is as follows: DNA is the molecule that carries genetic instructions. A gene is a specific segment of that DNA that codes for a protein or functional RNA molecule. This long strand of DNA is then tightly packaged and coiled around proteins to form a structure called a chromosome, which is located in the cell's nucleus.

Question 5

A scientist is studying the evolutionary relationships between four modern species (A, B, C, and D). By comparing a specific protein sequence, she finds the following number of amino acid differences when compared to a common ancestor: Species A has 3 differences, Species B has 15 differences, Species C has 8 differences, and Species D has 14 differences. Based on this molecular evidence, which two species most likely diverged from a common ancestor MOST recently?

Accepted Answer

Species A and C

Answer

Fewer differences in DNA or amino acid sequences indicate a closer evolutionary relationship and a more recent common ancestor. Species A (3 differences) and Species C (8 differences) have the fewest differences compared to the ancestor and to each other, suggesting they diverged more recently than the pairs with more significant differences (like B and D).

WCAS - Washington Comprehensive Assessment of Science Practice Test

WCAS - Washington Comprehensive Assessment of Science Practice Test

WCAS - Washington Comprehensive Assessment of Science Heredity and Biological Evolution Questions and Answers