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Citizen science and global biodiversity
Citizen science and global biodiversity

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2 Diversity

The variety of life on Earth is described by the term biodiversity, a shortened form of biological diversity, but the term doesn’t just refer to the number of species or individuals that can be found in a particular habitat. Biodiversity can be described at three major levels, the highest of which is ecosystem diversity.

An ecosystem can be small, like a rock pool, or immense, like a tropical rainforest. The set of organisms and non-biological components that are all linked by energy transfer and the cycling of components constitute the ecosystem.

Activity 1 Energy sources

Timing: Allow about 5 minutes

What sources of energy would be available to plants and animals in a small ecosystem such as a small wood? Suggest two examples for each.


For plants, the most obvious sources of energy are sunlight and nutrients from the soil. For animals, energy might be derived from eating plants or from preying on other animals.

There are of course other sources of energy within ecosystems, and as you read on others may occur to you. Taking the wood as an example, make a diagram showing routes of energy flow within the wood ecosystem.

Below the top level is the species diversity level, which describes the variety of species within an ecosystem. This is the level that you will be familiar with from its use in news and current affairs, whereby the loss of species through extinction reduces species diversity.

The lowest of the three levels is genetic diversity, which applies to diversity within a species. Within a population of organisms of a particular species, the genome of each individual organism is different. It is these differences that provide the possibility of evolutionary change, giving the species the potential to adapt to changing conditions in the future.

Activity 2 Genetic diversity

Timing: Allow about 5 minutes

In addition to genetic variation between individuals, there is a second component of genetic diversity. Suggest what this component might be. (Hint: think globally.)


Across a continent there may be separate populations of the same species. There can be genetic diversity between the populations, arising from adaptations to local conditions.

The study of diversity is dependent up knowing which organisms are present and how they are linked. You should now be able to appreciate how the identification of organisms is of paramount importance in studying biodiversity. It is impossible to make an accurate assessment of the state of an ecosystem or the vulnerability of a species without accurate species identification.