What is a species?
People intuitively recognise a species as a distinct kind of creature
or plant. Species are the basic units of diversity.
Put more technically, a species is a group of organisms with a unique set of characteristics, such as shape or behaviour, that distinguishes them from all other organisms.
Individuals within the same species can produce fertile offspring. But this definition is not hard and fast: some species can mate with other similar species and still produce fertile offspring.
Each species has a role within an ecosystem. So adding or losing a single species may have consequences for the whole system. But this is not always the case, as scientists working on NERC's Soil Biodiversity Programme discovered. They found that some micro-organisms could be removed from soil without noticeably affecting the rest of the ecosystem.
There could be between 10-100 million different species on Earth right now, but we have named only about 1·75 million. And because of duplications, the actual number is lower.
Different species can form when barriers such as an ocean or a mountain range isolate populations. But the barriers don't have to be huge and don't always need to physically isolate a population. NERC researchers found that coast and forest dwelling lizards on Martinique, a Caribbean island, interbreed less than expected, eventually creating new species.