WCAS - Washington Comprehensive Assessment of Science Heredity and Biological Evolution Questions and Answers — 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?
- These organisms evolved in similar environmental conditions, leading to similar structures.
- This is a coincidence, and the bone structures developed independently in each species.
- The different functions of the limbs caused the bone structures to become similar over time.
- These organisms share a common ancestor that had a similar forelimb structure. (Correct answer)
Correct answer: These organisms share a common ancestor that had a similar forelimb structure.
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:
- Acquired characteristics
- Natural selection (Correct answer)
- Genetic drift
- Artificial selection
Correct answer: Natural selection
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?
- Mutations are the ultimate source of new genetic variation in a population. (Correct answer)
- Mutations always result in traits that are harmful to an organism's survival.
- Mutations occur in response to environmental pressures to help an organism adapt.
- Mutations guarantee that offspring will be better suited to their environment than their parents.
Correct answer: Mutations are the ultimate source of new genetic variation in a population.
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?
- Chromosomes are made of genes, which are long strands of DNA.
- DNA is a segment of a gene, which is located on a chromosome.
- Genes are segments of DNA, which is tightly coiled to form chromosomes. (Correct answer)
- A gene is made of many chromosomes, which are composed of DNA.
Correct answer: Genes are segments of DNA, which is tightly coiled to form chromosomes.
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?
- Species B and D
- Species A and C (Correct answer)
- Species A and B
- Species C and D
Correct answer: Species A and C
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).
Question 6: Which of the following is the best definition of a biological adaptation?
- A change in an individual organism's behavior in response to a new environment.
- A short-term, non-heritable physiological change an organism makes to survive.
- A heritable trait that increases an organism's fitness in its specific environment. (Correct answer)
- A process where an entire population learns a new survival skill simultaneously.
Correct answer: A heritable trait that increases an organism's fitness in its specific environment.
A biological adaptation is a trait that is passed down genetically (heritable) and improves an organism's ability to survive and reproduce in its environment (increases fitness). Changes that occur within an individual's lifetime but are not passed to offspring, such as learned behaviors, are not considered biological adaptations in an evolutionary context.
WCAS - Washington Comprehensive Assessment of Science Heredity and Biological Evolution Questions and Answers
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?