-The word “ecology” was first defined by the German Zoologist Ernst Haeckel in 1869. it was derived from the greek word “oikos” meaning “house” or place to leave in.
Environment- Refers to the surroundings of an organism according to Richard Brewer.it is also called habitat. two Habitat features:• Biotic factors• Abiotic factors
-Basic to the study of ecology is the concept of ecosystem or the interrelateness of the physicall features and organisms occurring in a given area.
Three systems of interrelation between the biotic and abiotic features of the environment• Action- The physical environment acts on the community in many ways.• Reaction- refers to the effects of organisms upon their physical environment.• Coaction-refers to the effects an organism has on another.
According to Brewer, action, reaction, and coaction are the bases for thestructure and functioning of the community and the ecosystem.
R.D Mckenzie, in his definition of sociological ecology, pinpoints to the mutualism or the symbiotic relationship of human communities and the environment on which these are instituted.Horton and hunt,defines human ecology as the “study of man in relationship to his environment”.
Thomlinson in his study of population also explains that human ecology is broader than demography since it deals with the relations of the population to external factors and larger units, as well as with internal dynamics.