16.1.1B9. Organisms and their Environment

The Importance of Biodiversity — Combined Science 0653 - Biology Revision Notes & Topical Questions

5 min read 5 parts Lesson 5 of 6 Unit quiz

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Part 1 of 4Key ideas

Ecosystem

Ecosystem An ecosystem is a unit made up of a community of organisms and their environment, all interacting together.
A decomposing log and a lake are both examples.

Biodiversity

Biodiversity Biodiversity is the number of different species living in a particular area.
High biodiversity is needed for stable ecosystems, because there are many links in food webs and a loss of one species is easier to cope with.

Human pressure

Human pressure Human activities tend to push biodiversity down, and habitat destruction is one of the main causes.

Habitat destruction

Growing population

Growing population A larger human population needs more space for homes, food and resources, so rainforest, woodland and marine habitats are damaged.

Economic activities

Economic activities Land is cleared to make way for farming, mining, building and industry.

Pollution

Pollution Waste from human activities can poison habitats and make them unsuitable for the species that live there.

Broken food webs

Broken food webs If one species disappears, the animals that fed on it may starve, so more species are lost.

Deforestation is the clearing of trees, usually on a large scale.

It can be sustainable only if the trees are replaced by replanting.

Usually the land is cleared for another use, such as building, cattle grazing or palm oil plantations, so it is not sustainable.

A plantation of one crop supports far fewer species than the original forest, so biodiversity falls.

As the area covered by trees shrinks, the harmful effects on the environment grow.

Effect	Explanation (Extended tier)
Extinction of species	Habitats and food sources for animals and plants are removed, so some species have nowhere to live.
Loss of soil	Without roots to hold the soil, rain washes the topsoil away and nutrients are lost.
Flooding	Fewer trees take up and store water, so more rainwater runs quickly into rivers.
More carbon dioxide in the atmosphere	Fewer trees carry out photosynthesis, and burning or rotting trees releases carbon dioxide, which adds to global warming.

Term	Meaning
Ecosystem	A community of organisms together with the non-living environment they interact with.
Biodiversity	The number of different species living in a particular area.
Habitat destruction	The damage or removal of the place where organisms live.
Deforestation	The clearing of trees, usually on a large scale.
Sustainable	Able to continue without using up resources or causing long-term damage.
Monoculture	A large area planted with a single type of crop.

Defining biodiversity as the number of organisms. It is the number of different species.

Saying that replanting never helps. Deforestation can be sustainable if trees are replaced.

Listing only one effect of deforestation. Remember extinction, soil loss, flooding and carbon dioxide.

Forgetting that losing one species can cause others to die because their food source has gone.

Last updated: 20 October 2026