Crossing over produces modern combinations of alleles. Not unused alleles but unused combinations which can result in modern phenotypes or expanded assortment of phenotypes. This way the there's expanded genotype/phenotype variety but the genuine qualities are still the same ones.
Defective receptor on a cell membrane would have the least effect on Diffusion.
Ion pump. Active transport is molceules moving from low concentration to high concentration, requiring energy. Ion pump is in a process that uses the energy of an ion to move molecules against the gradient. Simple diffusion and facilitated diffusion are both passive transport. Bulk filtration would be endocytosis and exocytosis
