3.1.1Ecology and the Environment
Population, Community, Habitat and Ecosystem — Edexcel International GCSE Science Double Award (Modular) - Biology Unit 2 Revision Notes & Topical Questions
5 min read 7 parts Lesson 2 of 12
Section 1 of 7Levels of organisation in ecology
1Population
- Population A group of organisms of the same species living in the same place at the same time, for example all the badgers in a wood.
2Community
- Community All the populations of different species living in the same area at the same time.
3Ecosystem
- Ecosystem The community together with the non-living factors, all interacting in a given area.
Section 2 of 7Key definitions
Habitat
- Habitat The place where an organism lives.
- A woodland habitat might be home to badgers, deer, oak trees and ants.
Population
- Population Only one species is counted. The number of dandelions on a lawn is one population.
Community
- Community Species depend on each other for food, shelter, pollination and seed dispersal, so removing one species can affect the entire community.
Ecosystem
- Ecosystem An ecosystem includes all biotic factors and all abiotic factors interacting within an area.
- It can be as small as a garden pond or as large as Antarctica.
Section 3 of 7Biotic and abiotic factors
| Type | Meaning | Examples |
|---|---|---|
| Biotic | The living parts of an ecosystem | Plants, animals, fungi, bacteria, predators, competition |
| Abiotic | The non-living parts of an ecosystem | Light intensity, temperature, mineral ions, water availability, pH |
Section 4 of 7Worked example: a garden pond
Pond ecosystem
Population
- Population All the frogs in the pond form one population.
Community
- Community The frogs, fish, pondweed, snails and insect larvae together form the community.
Habitat
- Habitat The pond is the habitat of the frogs.
Biotic and abiotic
- Biotic and abiotic The living organisms are biotic factors, while water temperature, light and dissolved minerals are abiotic factors.
Section 5 of 7Using the terms in exam answers
1
Decide whether the question names one species (population), several species (community) or living and non-living things together (ecosystem).
2
When asked about abiotic factors, give specific examples such as light intensity, temperature or water availability, not just the word 'environment'.
3
When asked about a biotic factor, name the interaction, such as competition for food or predation by a fox.
4
If a species is removed, describe how its predators and prey would change, which shows the interdependence within a community.
Section 6 of 7Key terms
| Term | Meaning |
|---|---|
| Population | A group of organisms of the same species living in the same place at the same time. |
| Community | All the populations of different species living in the same area at the same time. |
| Habitat | The place where an organism lives. |
| Ecosystem | All the living and non-living factors interacting in an area. |
| Biotic factor | A living component of an ecosystem. |
| Abiotic factor | A non-living component of an ecosystem. |
Section 7 of 7Exam technique
1
Using population for several species; a population is one species only.
2
Writing that a community includes the non-living factors; that is an ecosystem.
3
Mixing up habitat and ecosystem; a habitat is where an organism lives, an ecosystem is the whole interacting system.
4
Listing dead organisms or soil as 'abiotic' without care; soil minerals are abiotic but decomposers living in the soil are biotic.
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