Populations and ecosystems

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Definitions

Ecology- The study of inter-relationships between organisms and their environment, including abiotic and biotic factors.

Biosphere- The life-supporting layer of land, air and water that surrounds the Earth.

Ecosystem- More or less self-contained functional units in ecology, made up of all the interacting abiotic and biotic factors in an area.

Population- A group of interbreeding organisms of one species in a habitat.

Community- All the populations of different organisms living and interacting in the same habitat at the same time.

Habitat- The place where a community of organisms lives.

Microhabitats- Smaller units within the habitat, which have distinct abiotic and biotic environmental factors.

Niche- The way an organism fits into it's environment, i.e all the abiotic and biotic conditions required for an organism to survive, reproduce and maintain a viable population.

Key points

The two major processes to consider when studying ecosystems are the flow of energy, and the cycling of elements through the system.

For example, in a lake, nutrients like nitrates and phosphates are recycled within the lake, and sunlight provides the plants with energy which then passes down the food chain to the animals. There is no loss or gain of these things from outside the lake.

The boundaries of a population are unclear, as groups of organisms fairly far away from each other could theoretically interbreed, but in practice they probably wouldn't so the different groups can be called separate populations.

There can be many habitats within the same ecosystem for example the leaf canopy will be the habitat for birds, whereas the forest floor would be the habitat for woodlice and insects.

No two species can occupy the same niche, even if they appear to because of intraspecific competition.

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