The smallest unit of an organism that is capable of showing the three attributes of life. The three main components of a eukaryotic cell are the cell membrane, the cytoplasm and the nucleus. A prokaryotic cell does not possess a nucleus. A multicellular organism consists of more than one cell (usually many more). A specialised cell is one which specialises in the performance of a particular function

ecological niche

Term describing the relationship between a species and its habitat, the other species in the community and its method of obtaining food and shelter.


The interrelationships between living organisms and their environment; also used to refer to the study of those interrelations.


Free-floating and mainly microscopic organisms, including some that use photosynthesis, and some that use other means to obtain their food.


The production by green plants (and some plankton) of compounds containing organic carbon from carbon dioxide and water, using the energy from solar radiation. Oxygen is produced as a by-product.