Which type of selection allows for the middle phenotypes to have increased fitness

Stabilizing Selection

Explanation:

There are 3 types of selection: directional, stabilizing, and disruptive.

Directional selection means that the animal slowly evolves from one extreme phenotype to the other extreme. For example, in horses, a horse could evolve from very weakling into a super strong and fast one.

Stabilizing selection means that the middle phenotype is chosen over the two extremes. For example, in babies, a too-low or a too-high birth weight are both bad, so a middle-weight is preferred.

Disruptive selection means the two extremes are chosen. For example, if there is a population of mice living in an area of sand and grasslands, the light colored mice can blend in with the sand, while the dark colored mice can blend in with the grass. However, the middle-colored mice cannot.

The only one that matches here is stabilizing.

Hope this helps!

stimulus is a change in the environment that causes an organism to react. the response is the reaction to the stimulus. some examples of stimuli for zebras are drought, to many predators, and bad feeding grounds such as dead grass or plants. zebras respond to stimuli just like all other living organisms