Betta (Betta splendens)
The wide color variations and finnage of betta fish arise from genetic variation. Human selection has proliferated desirable traits such as bright colors and large fins.
In nature, environmental factors such as temperature are selecting agents. Traits that benefit an animal increase its chance of survival. Individuals exhibiting desirable traits are therefore more likely to pass on their genes (and the trait). Overtime, that trait becomes prominent in a population.
Chantal Wagner Cornin on Flickr












