Ecological studies are based on three principal aspects viz., Taxonomic affinities. Habitat and Levels of organisation. Accordingly, ecology may be sub divided into the following.
(1) Based on taxonomic affinities, ecology may be divided into Plant ecology and Animal ecology. Modem studies however do not distinguish between these two as both plants and animals are also interdependent.
(2) Based on Habitat, ecology may be classified into fresh water ecology, marine ecology, forest ecology etc.
(3) Based on levels of organisation, ecology may be sub divided into Autoecology and Synecology.
Autoecology is the study of an individual organism and its relationship with the environment. It may be called ecology of individuals. In autoecology, individuals are the units of study. Individuals are studied for details of their distribution, morphology, pattern of life cycle and the environmental factors which influence these.
Synecology is the study of groups of organisms together with reference to their environment. Here, groups of organisms rather than the individual constitute the units of study. Since organisms live in nature as groups and not as isolated individuals, synecology is believed to reflect the natural conditions better than autoecology. Synecology also takes into consideration the interactions between organisms.
Synecology may be further sub-divided into, population ecology, community ecology, ecosystem ecology etc.