Ecology is the scientific study of the interactions of living organisms and their environments. These interactions are studied with a view to discovering the principles which govern them.

It is important for humanity to understand its environment because we have the ability to modify the environment through the use of technology, and through overexploitation of natural resources as a result of greed or sheer pressure of numbers. Therefore, ecology is more than just the understanding of the interrelationships between organisms and their environment; it also has social, political, economic and technological dimensions.

Ecology is also the branch of biology that draws all of the other components together. It demands a synthesis of physiology, anatomy, morphology, genetics and other aspects of biology that have been studied in detail as separate entities throughout your first year course. Although ecology retains an analytical approach of its own, it also brings the pieces of the biological puzzle together in a synthesis.

Just as biology is assembled from various parts, so can ecology be studied at different levels, from organism to biome to biosphere. Most ecologists, however, work from the level of population through biome.

A population is a group of individuals of the same species which can freely interbreed and are found together in a particular place. A key feature of populations is that members of a population are more likely to interact with other members of the same population than they are with members of a different population of the same species living in a different place.

An ecosystem is a more-or-less self contained ecological entity, consisting of both organisms and their complete biotic and abiotic environment found in a particular place. It is the smallest functional ecological unit within the biosphere. An ecosystem is a relatively independent, relatively self-contained, and more-or-less self sufficient unit. A key feature of ecosystems is that members of a particular ecosystem are more likely to interact with other members of the same ecosystem than they are with members of a different ecosystem of the same or different type found in a different place.

A community may be thought of as the living (biotic) component of the ecosystem. It consists of a number of populations of different species found in a particular place. The term 'community' is sometimes used in another, entirely different context; that of populations of similar organisms (e.g. the bird community of a lake, seashore or forest). The concept of community, however it is used, has as its main focus the study of biotic interactions.

A biome involves the linkage of ecosystems into regional classes, which have similar characteristics. For example, grassland biomes in similar climatic areas of the world have similar characteristics as pertains to temperature regimes, rainfall, fire cycles, etc. The smallest biome in the world is the fynbos biome, which is found only in the southwestern part of South Africa. The biome concept has not been applied to groupings of ecosystems in aquatic environments, although it is possible to make such groupings.