Habitat - The place or set of environmental conditions which an organism inhabits. Species - A group of organisms which interbreed and produce fertile offspring. Darwin's theory of evolution - 1. Variation must be heritable. Excess production of young must result in struggle for survival.
Fittest variants survive better.
Change in individuals as survivors breed. Predation - When an animal kills and eats another animal. When an animal eats a plant. Parasite - An organism that derives nourishment from its host without killing it. Commensal - One organism benefits, while the other is not harmed.