Exam 16: How Populations Evolve

Imagine that two men and two women settle on an uninhabited island, no new settlers arrive, and nobody leaves the island for many generations. All four of the settlers have brown eyes, but one of the men carries a recessive gene for blue eyes. Eye color has no effect on fitness. If the percentage of blue-eyed individuals on the island increases from 0% to 25%, what is the probable cause?

A population of plants comes in two flower colors: blue and white. Crossing two blue-flowered plants produces mostly blue-flowering offspring and some white-flowering offspring. Crossing two white-flowered plants produces only white-flowering offspring. This indicates that the white-flowering plants are

Evolutionary adaptations are not always the ʺbestʺ solution to a problem. Explain how the long necks of giraffes can be both advantageous and disadvantageous.

The nonliving components of an environment, such as weather and water availability, are

A population that maintains several different phenotypes of the same trait displays__________.

A bird comes in a range of phenotypes, from white through gray to black. Disruptive selection favors the gray phenotype.

How does the founder effect influence the frequency of alleles in a population?

A flock of birds with various beak sizes migrates to a new island where their traditional food is not available. However, there are plants that produce a variety of large nuts, which can be eaten by birds with the largest beaks, and plants that produce a variety of small, soft seeds, which can be eaten by birds with the smallest beaks. Over time, this population divides into two species with large and small beaks. This is an example of

Antibiotic resistance is a result of __________in bacteria.