Individuals and species

Within the biosphere, living things are organised from a simple level to a complex one. The levels can be set out as a flow chart:

Individual Population Community Ecosystem Biosphere

Figure to be added

Figure 15.1 — the levels of organisation in the biosphere: an elk (individual), a herd of elk (population), elk with bears, birds and other animals (community), the whole valley with its river and mountains (ecosystem), and the Earth (biosphere).

Individual

A single living thing belonging to some species that lives in the environment is an individual. Examples: a coconut tree, an elephant.

Species

A species is a group of living things, very similar in form, that can interbreed and produce fertile offspring.

Assignment 15.1

Choose a suitable part of your home garden or school grounds and name the species that live there.

For example: coconut palm, mango tree, grass, hibiscus; earthworm, black ant, butterfly, garden lizard, crow, squirrel, snail, spider.

Why fertile offspring is the test

Looking alike is not enough to be one species: a male and a female of the same species can look very different, and some different species look almost the same. The test is breeding. A horse and a donkey can mate, but their offspring, the mule, is infertile and cannot breed, so horses and donkeys stay separate species. All the dogs in the world, from a small pet to a large guard dog, can interbreed and have fertile puppies, so they are one species. When you list the species in your garden, you are counting kinds of living thing that breed only among themselves.

Individual and species

An individual is one living thing; a species is a group of similar living things that can interbreed and produce fertile offspring.