Genetic Diversity
Genetic diversity between organisms
Selective Breeding
The Founder Effect
Genetic Bottlenecks
Genetic diversity between organisms
The genetic diversity between organisms is accounted for by variation in DNA. Even a tiny difference in DNA can result in a lot of variation. What’s more, even identical DNA can still result in variation due to certain genes being active and others not. Is it visible that these two have largely identical DNA?
Nope. Yet when compared to bacteria or an imaginary alien, those two above definitely look more closely related. So the similarities between human DNA and chimp DNA cause the visible and functional (phenotypical) similarities such as limbs, eyes, mouth, etc. while the differences in DNA result in the phenotypical differences such as hair thickness, facial features and so forth.
Selective Breeding
Plants are selectively bred for higher yields, while animals are bred for many different purposes, such as food production, competitive events, aesthetic features, etc.