biotic

features of the enviroment that are alive or were once alive.

abiotic

nonliving features of the enviroment

climate

an area's average weather conditions

watershed

an area of land from which rainwater and snowmelt run off toward a particular stream or river.

Hypoxia

low oxygen in the water

water cycle

a model that describes how water leaves the earth and then returns.

nitrogen cycle

a model of the process of nitrogen transfering from air to soil to the organisms.

carbon cycle

a model of the process of carbon going from the air to ground to plants to humans.

estuary

a place where salt water from the ocean mizes with fresh water from river s and the land.

Food web

a modelthat shows all the possible feeding relationships in a community.

Energy pyramid

shows the amount of energy at each level of a food chain.