Question 1

Which of the following statements best explains why rotating branches around a node in a cladogram does NOT change the relationships among the organisms?

Accepted Answer

Because the order of the tips is arbitrary and only the branching pattern (nodes) shows relationships.

Question 2

A researcher is building a cladogram using a trait table for five plant species. One trait, 'xylem & phloem,' is present in all five species. Where should this trait be marked on the cladogram?

Accepted Answer

At the base of the tree, before any branches split.

Question 3

Two DNA sequences are compared: Sequence A: ATGCCGTA and Sequence B: ATGTCGTT. How would you calculate the sequence divergence between these two sequences?

Accepted Answer

Count the number of differences, divide by total positions, and multiply by 100: $$\frac{2}{8} 	imes 100 = 25\%.$$

Question 4

Which of the following is an example of convergent evolution?

Accepted Answer

Wings in bats and birds, which evolved independently in response to similar environmental pressures.

Question 5

A fossil species is found to have a short, broad upper pelvis and a grasping foot. What can you infer about its locomotion and evolutionary significance?

Accepted Answer

It likely walked upright but also climbed trees, representing a transitional form between arboreal and bipedal locomotion.

Question 6

Why is it incorrect to say, 'The population needed the trait, so it appeared,' when explaining the evolution of a new trait?

Accepted Answer

Because mutations are random and do not occur in response to a population's needs; selection acts on existing variation.

Question 7

In a high-UV environment, which selective pressure most strongly influences the evolution of skin color, and why?

Accepted Answer

Protection of folate, because high UV can degrade folate, and darker skin protects against this.

Question 8

A scientist finds that two species share a similar bone structure in their forelimbs, but use them for different functions. What is the best explanation for this observation?

Accepted Answer

They inherited the bone structure from a common ancestor, but natural selection led to different uses (homologous structures).

Question 9

Which of the following best describes the principle of parsimony when building a cladogram?

Accepted Answer

The simplest explanation with the fewest evolutionary changes is preferred.

Question 10

A population of lizards lives on an island with dark volcanic rock. Over generations, the frequency of dark-colored lizards increases. Which process best explains this change?

Accepted Answer

Natural selection favored dark-colored lizards because they were less visible to predators, leading to increased survival and reproduction.

Question 11

Which of the following is a vestigial structure in humans, and what does its presence indicate?

Accepted Answer

The coccyx (tailbone); it indicates descent from ancestors with tails.

Question 12

If a trait is present in all but one species on a cladogram, what is the most parsimonious explanation for its distribution?

Accepted Answer

The trait evolved once in the common ancestor and was lost in the one species that lacks it.

Question 13

A scientist compares the amino acid sequences of a protein in four species and finds the following number of differences: A-B: 2, A-C: 5, A-D: 7. Which species is most closely related to species A?

Accepted Answer

Species B, because it has the fewest differences with A.

Question 14

Why does the skin color prediction model use ancestral populations rather than people who recently moved to a new location?

Accepted Answer

Because natural selection requires many generations to shape traits to local environments.

Question 15

Which of the following is a correct statement about the relationship between UV exposure, folate, and vitamin D in human evolution?

Accepted Answer

High UV favors darker skin to protect folate, while low UV favors lighter skin to produce enough vitamin D.

Question 16

A population with a traditional diet rich in vitamin D (such as the Inuit) has darker skin than predicted by the skin color model for their latitude. What is the most likely explanation?

Accepted Answer

Their diet reduces the selective pressure for lighter skin, so darker skin persists.

Question 17

Which of the following best explains why skin cancer was probably not a major selective pressure in the evolution of human skin color?

Accepted Answer

Because skin cancer usually occurs after reproductive age, so it does not strongly affect reproductive success.

Question 18

Which of the following is NOT a requirement for natural selection to occur in a population?

Accepted Answer

All individuals must acquire the same traits during their lifetime.

Question 19

A scientist finds a fossil with both fish-like fins and limb bones similar to those of tetrapods. What is the significance of this fossil?

Accepted Answer

It is a transitional form, showing the gradual change from fish to tetrapods.

Phylogeny, Common Descent, and Natural Selection: Study Guide

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