AP Biology Name/Hr: _________________________"
Evolution by Natural Selection
What are some differences you have noticed in the size and shape of dogs in your neighborhood?
They could be different size, different hair color, different shape…
Do their differences make them better at some things, but not well suited for others?
Certain traits may be more favorable for certain actions. For example some might be better at tracking scents, or
chasing other animals.
What would happen if the world suddenly changed, so the only thing that dogs could eat was deer and there was
absolutely no way for a dog to eat if it wasn’t big or strong enough to catch and kill a deer?
Traits like speed an strength would be selected for leading to strong and fast dogs to express higher fitness. Thus the
gene pool would start to shift towards faster and stronger dogs, and the small, slow and weak dogs would start to be
phased out.
Next, think about the mice shown below. Using the space below, describe what is happening in figures 1-3.
Figure one shows overproduction of mice, which also express variation. The variation shown is their hair color; some
being whie while others darker and blending in with the ground.
Figure two shows a environmental selection pressure in terms of the bird acting as a predator to the different mice. As
one can see the white mice stick out in their surroundings and would be more likely to eaten by the bird.
Figure three shows most of the white mice, who have the least favorable trait of being white, being removed from the
population. This reduces the population, leaving less compitition for the darker mice. This would lead to the darker
mice expressing greater fitness than the white mice, which would result in a genetic shift towards the darker mice.
