OCR F215 Ecosystems

Ecosystems notes for Unit 2 of OCR A2 Biology

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What is an ecosystem?
A group of living organisms and non-living things occurring together, and the
interrelationships between them can be described as an ecosystem.
The components of an ecosystem are:
Habitat ­ the place where the organism lives.
Population ­ all organisms of one species that live in the same habitat at the
same time and can breed together.
Community ­ all populations of different species that live in the same
habitat at the same time and interact with each other.
Ecosystems are dynamic. Populations rise an fall, sometimes only slightly and
sometimes very noticeably. This is due to the fact that because the community
interact with each other and therefore changes in the population of one factor can
affect the population of another.
If a predator's population rises then the population of its prey will fall.
Nitrogen levels affect what plants can grow. In low nitrogen environments,
nitrogen-fixing plants grow well. These plants will increase the soil nitrogen
level therefore allowing other plants to survive in that environment also.
The way in which living organisms affect one another are described as biotic factors,
these include food supply, predation and disease. Abiotic factors describe the
effects of the non-living components of an ecosystem on living organisms; these
include pH, temperature and soil type.
Energy and ecosystems
Matter is recycled within and ecosystem. All energy within an ecosystem originally
came from sunlight.
Plants and other photosynthetic organisms supply chemical energy to other
organisms they are producers.
Primary consumers are herbivores and consume the producers.
Secondary consumers are carnivores and eat primary consumers. These are
consumed by tertiary consumers.
Decomposers feed on dead organisms or waste material.


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