What happens to a species if its genetic diversity is low?

Dominance the dominant allele doesn’t fully mask or hide the recessive. for example, a red carnation with a white carnation will produce a carnation. one gene one trait. well most of the time than one gene controls a trait. we are all different but genetically speaking we are % similar with regards to genetic makeup.

What type of cell is produced after fertilization occurs and the gametes combines ?

Why is excretion necessary to maintain homeostasis?