Natural Selection Review

Conservation biologists studying cheetah populations have determined that the lack of genetic diversity among the cheetahs is due to genetic drift.

Which statement explains the most likely consequence of having a low genetic diversity on the cheetah population?

• The chances of a mutation occurring in the cheetah population are decreased, increasing the cheetah survival rate.

• The gene pool remains in equilibrium and future generations of cheetah offspring are stronger and better adapted to their environments.

• The cheetah population becomes less likely to survive an outbreak of a disease or an environmental change, increasing the chance of species extinction.

• Genetic variability is maintained from older cheetah populations that have survived and endured environmental stressors.

Common baboons live on the savanna in breeding groups called troops. While females tend to stay with the troop, younger or less dominant males may leave to join a neighboring troop. Which of these is a likely outcome of movement by young males?

• Gene flow occurs between populations.

• Allele frequencies suddenly change.

• Relative genotypic frequencies reach a constant state.

• Intermediate phenotypes increase in the species.

Two populations of mice living in the same forest are separated by a large water-filled ditch. After a rainstorm, flooding brings several mice from one population to the other population. When the mice from the first population reproduce with members of the second population, which of the following will likely occur?

• All the offspring will die as a result of reproductive mutations.

• The offspring will be forced to leave the second population.

• The offspring will be genetically identical to their parent from the first population.

• The offspring in the second population will have greater genetic variety.

Lord Howe Island is a volcanic island in the Tasman Sea that is about 11 km long and 2.8 km wide. The island has two species of palm trees, Howea forsteriana and the more abundant Howea belmoreana . The two species do not interbreed even when they grow very close to each other. Which evolutionary process fails to occur?

• Genetic drift of Howea forsteriana

• Natural selection of adaptive traits in both species

• Gene flow between the two species

• Mutations in Howea belmoreana

The concept of gene flow is demonstrated when a cow is driven off from its herd, joins another herd, and reproduces. When the cow contributes to the gene pool of the new herd, which of these most likely increases?

• Natural selection

• Genetic variation

• Environmental fitness

• Reproductive mutations

A new predator of rabbits has been introduced within an ecosystem. This new predator runs faster than the native predators of rabbits.

Which statement describes what will most likely occur in the rabbit population due to the introduction of the predator?

• The rabbits will mutate their genes and express genes that increase their speed.

• Slower rabbits will develop stronger legs and pass this trait to their offspring.

• Rabbits will mate and produce offspring with a different species that has faster runners.

• Faster rabbits will survive and reproduce increasing the average speed of the rabbit population.

Adaptations that result from natural selection are expected to increase the fitness of an organism. In terms of natural selection, which of the following best describes fitness?

• Being able to escape from predators

• Being among the strongest organisms in a population

• Being able to survive, find a mate, and produce offspring

• Being able to survive long enough to reach the adult stage

The white cattail is a hybrid species of plant that is a result of the cross between the broad-leaved cattail and the narrow-leaved cattail. Over time, the white cattail has established itself in the wetlands of Midwestern states.

Which of these explains the success of the white cattail?

• Favorable genes from parental generations provide advantageous characteristics to the hybrid species.

• Hybridization produces offspring traits that allow different species to survive in extreme environments.

• Inherited traits passed on from parental generations make hybrid species more susceptible to disease.

• Hybrid species display more adaptations due to their reduced genetic diversity.

The table shows the survival rate of two types of beetles in the same environment over a period of three years.

Which statement about the beetles in this environment is best supported by the data?

• Green beetles are more fit for the environment than brown beetles are.

• Brown beetles undergo a greater number of unfavorable mutations than green beetles do.

• Green beetles have a greater gene frequency among their population than brown beetles have.

• Brown beetles have a shorter life cycle than green beetles have.

In the 1940s, the scientist J. B. S. Haldane linked many human red blood cell disorders with the tropical regions where malaria occurs. Haldane hypothesized that the widespread presence of these red blood cell disorders as well as traits that protect individuals from malaria were the result of natural selection. Haldane’s hypothesis was later confirmed by the research of A. C. Allison.

The resistance to malaria carried by individuals in areas where malaria is widespread is the result of —

• a vaccine against malaria

• the individuals’ genetic composition

• antibiotic medications

• the individuals’ behavior in avoiding those with the infection