Evolution

Which of the following is a factor in natural selection?

• Individuals of species compete with one another to survive.
• All species are genetically diverse.
• Individuals better able to adapt to changes leave more offspring.
• All of the above.

The fossil record provides evidence that

• Fossils cannot be dated.
• All species were formed during Earth’s formation and have changed little since then.
• The fossilized species have no connection to today’s species.
• Older species gave rise to more-recent species.

Individuals that are better able to cope with the challenges of their environment tend to

• Decrease in population over time.
• Leave more offspring than those less suited to the environment.
• Leave fewer offspring than those less suited to the environment.
• Both (a) and (c)

Members of different subspecies

• Are considered to be entirely different species.
• Can no longer interbreed successfully.
• Differ genetically because of adaptations for different living conditions.
• Will never diverge to become different species.

Starting in 1954, commercial fishers in the northwest Pacific were paid by weight, rather than by the individual fish, for pink salmon. The fishers increased the use of a type of net that selectively catches larger fish. Which of the following effects did this change in fishing technique most likely have on the salmon population over the next 20 years?

• The average body size of the salmon population decreased significantly.
• The average body size of the salmon population increased significantly.
• The average body size of the males in the salmon population increased, and the females stayed the same.
• None of the above.

European rabbits were introduced to Australia in 1859. The rabbits reproduced rapidly in their new habitat, displaced other animals, and overgrazed vegetation. In an attempt to reduce the rabbit population, a virus was introduced in 1951. This virus is usually deadly to European rabbits. When the virus was first introduced, the rabbits died in large numbers, but the death rate decreased over time. Which of the following best explains the decrease in the rabbit death rate?

• Young rabbits learned to avoid being infected with the virus.
• The lifespan of the virus was too short to affect rabbits over a long period of time.
• Natural selection favored rabbits that were resistant to the virus.
• None of the above.

Which of the following statements gives the most likely explanation for the presence of two very similar species of squirrels living on opposite sides of the Grand Canyon?

• One squirrel traveled across the canyon and started a new population on the other side.
• One squirrel traveled across the canyon and interbred with a different population on the other side.
• Members of one single squirrel species were geographically separated by the formation of the canyon.
• Members of two different squirrel species migrated from two different places to opposite sides of the canyon.

The Asian shore crab invaded parts of the eastern coast of the United States about 15 years ago. The Asian shore crab preys on blue mussels. In the time since the Asian shore crab arrived, the average shell thickness of the blue mussel population has increased. Which of the following is the most likely reason that this increase in shell thickness has occurred?

• Blue mussels with thick shells attract more crabs that mussels without thick shells.
• Blue mussels with thick shells grow in larger colonies than mussels without thick shells.
• Blue mussels with thick shells catch more food per day than mussels without thick shells.
• Blue mussels with thick shells survive and reproduce more successfully than mussels without thick shells.

Some willow trees alter the chemical composition of their leaves when attacked by caterpillars. Compared to normal leaves, the chemically altered leaves are less nutritious and more difficult for caterpillars to digest. Which of the following is a likely effect of this ability to alter leaf composition?

• Willow trees with this ability will attract more caterpillars than other willow trees.
• Willow trees with this ability have a survival advantage over other willow trees.
• More butterflies will lay their eggs on willow trees with this ability than other willow trees.
• None of the above.

Structures that share a common ancestry or are similar because they are modified versions of structures from a common ancestor that contain the same basic bone structure are (a)  

• Not related.
• Not homologous.
• Homologous.
• Young in origin.