Ecosystems & Niches (Cambridge (CIE) A Level Biology): Revision Note

Ecosystem & Niches

Ecosystems

• Species do not exist by themselves in their own isolated environment, they interact with other species forming communities

• These communities interact with each other and the environment they live in, forming ecosystems

• An ecosystem is a relatively self-contained community of interacting organisms and the environment they live in, and interact with

• There is a flow of energy within an ecosystem and nutrients within it are recycled

• There are both living (biotic) components and non-living (abiotic)components within an ecosystem

• Ecosystems vary greatly in size and scale

  • Both a small pond in a back garden and the open ocean could be described as ecosystems

  • A human being could also be described as an ecosystem; there are thousands of species of bacteria living on and in every person

• Ecosystems vary in complexity:

  • A desert is a relatively simple ecosystem

  • A tropical rainforest is a very complex ecosystem

• No ecosystem is completely self-contained as organisms from one ecosystem are often linked to organisms from another

  • For example, birds are able to fly long distances to feed from multiple ecosystem

Example of an ecosystem

• A forest is a perfect example of a complex ecosystem

• There is a large community of organisms including trees, birds, small and large mammals, insects and fungi

• The non-living components of the ecosystem include: the soil, dead leaves, water from the rain and streams, the rocks and any other physical or chemical factors

• The non-living components of the ecosystem influence the community of organisms

A forest ecosystem

Photographed by  Tom Harpel, CC BY 2.0, via Wikimedia Commons

Niche

• The place where a species lives within an ecosystem is its habitat

• The role that species plays within an ecosystem is its niche

  • It encompasses where in the environment the organism is, how it gets its energy and how it interacts with other species and its physical environment

  • This is how an organism fits into the ecosystem

Example of a niche

• A dung beetle (example species Scarabaeus satyrus) occupies a very specific niche within its ecosystem

• Dung beetles have learned to exploit the dung (faeces) of animals as a food source and they have a characteristic behaviour of rolling the dung into balls before transporting it to their underground burrow for storage as food

• Their behaviour within their ecosystem has many knock-on effects on the environment and other organisms living in it

• The burrows and tunnels that they create turns over and aerates the soil

• The buried dung releases nutrients into the soil both of which can benefit other organisms like plants

• The transportation of the dung underground by the beetles also helps to keep fly populations under control

A dung beetle occupies its niche by feeding on faeces and recycling nutrients

Achiri Bitamsimli, CC BY-SA 4.0, via Wikimedia Commons