What is similar about a dominant trait and a recessive trait

The only real similarity between the two is that both dominant and recessive traits are inherited by the offspring. This just means that a child will get dominant and recessive traits from each parent. You may only see the effects of the dominant traits, but that doesn't mean the recessive traits aren't there.

any abiotic or biotic factor in an ecosystem that causes a population's size to slow or decrease is a limiting factor.