Ecology is the study of the relationships between organisms and their environment. It examines biotic factors like other organisms as well as abiotic factors such as climate and geology. Organisms interact with their environment through a process of action, reaction, and coaction. Action refers to how the environment affects organisms, reaction is how organisms affect the environment, and coaction is how organisms interact with each other. Ecology also examines human communities and how they relate to and depend upon their surrounding environment.

1. The Nature of Ecology

2. -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.

3. Environment
- Refers to the surroundings of an organism
according to Richard Brewer.it is also called
habitat.
two Habitat features:
• Biotic factors
• Abiotic factors

4. -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.

5. 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.

6. According to Brewer, action, reaction, and
coaction are the bases for thestructure and
functioning of the community and the
ecosystem.

7. 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”.

8. 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.

9. Ecological Process