Biotic factors and abiotic factors are what make up an ecosystem.

Abiotic factors are the nonliving parts of an ecosystem like sunlight, water, oxygen, temperature and soil.

Biotic factors are things that are living or where once living. Birds, insects, mammals, reptiles are biotic factors. Along with animals, plants like grass and trees are also biotic factors.

Now, biotic factors aren't just living things, they are also things that were once living. So, a dead fish is a biotic factor because it was once living. A leaf that falls off a tree is a biotic factor as well.

Biotic factors are also things that come from living things. For example, horse manure is a biotic factor because it came from a living horse.

In an ecosystem, biotic factors need abiotic factors to survive. A plant couldn't live without sunlight, just as a deer couldn't live without water. Take away the abiotic factors, and you take away the ecosystem.