Definitions of Species (Cambridge (CIE) A Level Biology): Revision Note

Definitions of species

Biological species concept

• Scientists have been classifying organisms into species for hundreds of years, in order to investigate the diversity of life that exists today and in the past

• There is difficulty in determining whether new organisms discovered belong to an existing species, or a new one

• This is because the most widely accepted definition of a species is:

  • A group of organisms with similar morphological and physiological features that able to breed together and produce fertile offspring

• This is the biological species concept, and is reliant on determining whether interbreeding produces fertile offspring - this is difficult and time-consuming to determine in practice

• However there are other discriminating factors that scientists can use to group similar organisms together

Morphological species concept

• In the past, most scientists described organisms by their physical features (morphology) as these can be more easily observed

• They group together organisms that share many physical features that distinguish them from other species

• This is the morphological species concept

Ecological species concept

• An ecological species is a group of organisms that share the same ecological niche (for example, the same diet, habitat and role in the ecosystem), which is different from the niche of any other species

• This is the ecological species concept