Mosquitoes of a white-speckled variety feed upon cattle as they are freighted from the Midwest to a ranch in the Southwest. After arriving at the new location, the speckled mosquitoes join an existing mosquito population, in which non-speckled individuals outnumber speckled individuals 3:1. Over time, though, the speckled trait increases in frequency in the population, with the number of speckled individuals ultimately equaling the number of non-speckled individuals.

A goldfish pond contains two varieties of algae: one that the fish like to eat and another (which has an unpleasant flavor) that the fish tend to avoid. Over time, the unpleasant tasting algae occupies more of the pond than the tasty algae.

A population of bats in a mining cave has two distinct phenotypes for tongue length: short and long. An accidental explosion results in the deaths of numerous bats. By chance, most of the bats killed are short-tongued bats. This leads to an increase of the long-tongued trait in this bat population.

We’ve determined the random mishap that caused the long-tongued trait to increase in the bat population is an example of genetic drift. Which form of genetic drift does this particular scenario represent?

A child from a house infested with both low- and high-jumping fleas goes to another house for a play date. Several low-jumping fleas happen to be on a stuffed animal that the child takes with her. A few weeks later, the house where the play date took place becomes infested with a population of low-jumping fleas.

We’ve determined that the previous case with the low-jumping fleas is an example of genetic drift. Which form of genetic drift does this scenario represent?

A mutation in the cells of a bird’s eye allows it to distinguish window glass from open air. Although this mutation gives the bird the advantage of being able to avoid flying into panes of glass (often a deadly proposition for birds), this beneficial trait will not be subject to natural selection. Why?

In a wheat field, a population of wheat-eating insects reproduces year round. Green-colored individuals in this insect population thrive in the spring when they are the same color as young wheat and can avoid predation by birds. Brown-colored individuals thrive in the fall when they are the same color as mature wheat, thereby allowing them to avoid predation by birds.
Neither green nor brown coloration will be subject to natural selection. Why?