Ecology is the study of the interactions of the abiotic (non-living) and biotic (living) factors in an area. Organisms of a species make up a population; different populations make up a community; all the communities in a given area interact with one another and the abiotic environmental factors such as amount of water, sunlight, temperature and soil composition makes up an ecosystem. The ecosystem is the basic unit ecologists focus upon. Within an ecosystem, an organism has its habitat (where it lives) and its niche (the role it plays).
Ecosystems are dynamic in nature; their characteristics can vary over time. Disruptions to any abiotic or biotic factor of an ecosystem can lead to shifts in all its populations and changes in its interactions. A biome is made up of many generally similar ecosystems that have generally similar producer species, soil and climates in a geographic area. Terrestrial biomes include tundra, taiga, grassland, desert, temperate (deciduous) forest, savanna and tropical rainforest. Aquatic biomes include estuary, freshwater and marine.