19.1 - Ecosystems

Ecology vocabulary and levels of organisation

In ecology, organisms are studied at several levels of organisation, building up from the smallest to the largest.

The levels, from smallest to largest

• Individual organism - A single living thing, such as one mouse
• Population - All the organisms of one species living together in the same place at the same time, e.g. all the mice in a field
• Habitat - The place where an organism lives, such as a field, a forest, or a rocky shore
• Community - All the populations of different species living and interacting together in one habitat or ecosystem - not just the mice, but the owls, the plants, and every other species there
• Ecosystem - The interaction of a community of living organisms with the non-living parts of their environment

The variety of all the different species of organisms on Earth, or within an ecosystem, is called biodiversity.

Biotic and abiotic factors

• Biotic factors - The living parts of the environment
• Abiotic factors - The non-living parts of the environment

An ecosystem brings together the habitat, the community that lives in it, and the biotic and abiotic factors that act on it.

An organism's niche

• The niche is the particular role an organism plays within its community.
• It covers:
  • The resources it needs, such as light and nutrients
  • The conditions it can tolerate, such as temperature
  • Its interactions with other organisms, including competition and predation