First things first

A population primer

Very few things on this planet live alone. That’s why it’s important to study populations: to understand how groups of people, animals, plants, bacteria and other living things survive and behave in the real world.

We study populations to learn how diseases spread, how we can stop rare animals becoming extinct, how we are related to one another and how humans and other species are affected by environmental change.

When we talk about populations, we might be grouping together all the individuals of a species, as in ‘the global population’, or we might be talking about a group living in a particular ecosystem or environment. You can even refer to the populations of bacteria living on your toothbrush.

The group or its habitat (where it lives) can be big or small, but typically the term population only ever refers to one species. So you will have a number of different populations of bacteria living on your toothbrush, each from a different species. These different populations form a larger community of bacteria that, together with the environment provided by your toothbrush, create a miniature ecosystem right there in your bathroom – just like in woodland or on a coral reef. Some species of bacteria might be unique to your toothbrush, while others might be related to populations of bacteria in your back garden or at the bottom of the ocean. 

Scientists often try to understand patterns within populations or differences between them. They might look at human population growth in China or differences between populations of salmon in separate rivers. It’s not always obvious what causes change or variation between populations, because in the real world there are so many factors to consider. But that’s what makes studying populations so fascinating.

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About this resource

This resource was first published in ‘Populations’ in June 2014.

Ecology and environment
Education levels:
14–16, 16–19, Continuing professional development