Unit 7: Topic 2 - Natural Selection

Question 1

How does natural selection relate to phenotypes in populations?

Answer 1

More favorable phenotypes have greater fitness. The organisms with greater fitness will pass on their similar traits to their offspring.

Question 2

How does an environment apply selective pressure to a population?

Answer 2

Terrain or weather will determine which phenotype is naturally selected for, and apply selective pressure to the organisms needing to adapt to survive. For instance, a white-furred rabbit would be selected over a brown-furred rabbit in a snow-tundra environment (due to predators spotting the brown fur much faster than white fur). In this example, the brown-furred rabbit would be naturally selected against. The environment can also limit the growth of the population. For instance, if there is insufficient space for organisms to reproduce further, the population size is limited and the organisms which have the greatest fitness will be selected for.

Question 3

What is an example of an organism’s phenotypes substantially increasing/decreasing their fitness depending on the environment?

Answer 3

Any example in which a phenotype determines whether the organism would be able to survive in that specific environment. Some examples include white-furred/brown-furred rabbits in a snow environment, mice color in different environments, longer claws on a predator, etc.