A couple of examples are: - how they look (brighter colors, more spots, etc.) in order to attract more mates - adapting to different food sources (look up the varying finch beaks throughout the Galápagos Islands based on their food source) so they can survive long enough to reproduce - camouflage to hide from predators to survive long enough to reproduce
There are two kinds of food chains one starting with autotrophs, the grazing food chain, and the other starting with dead organic matter, the detrital food chain.
