Ecology – Organisms and Populations

Ecology – Organisms and Populations


The term ecology was given by Ernst Haeckel in the year 1989.

Ecology is the branch of biology that deals with inter-relationship amongst organism and their environment. it is connected with the study of environmental factors, plant adaptations, and effect of plants on the environment.

Important Branches of ecology


It is the study of an individual or species.

  • Autecology is the study of inter-relationships between a species/individual and its environment in all stages of its life cycle.


It is the study of organisms which are associated as a unit.

  • Synecology is the study of inter-relationship between environment and individual animal.
  • It is the study of biotic community in relation to an environment of a place.

Note – The term autecology and synecology were given by Schroeter and Kirchner in 1896.

Level of organization

Individual (Organism)

The individual organism is the basic unit of ecological hierarchy.


The population is the group of similar organism in the given area. The different population of same organism present in the particular area is called local population.

Biotic or Biological community

Biotic community is the group of the population of different species in a given area that interact with one another through competition, predation, mutualism. Pond community is an example of biotic community.


The ecosystem is a whole biotic community in a given area including its abiotic environment. In an ecosystem, the biotic community and the physical environment both interact and exchange material as well as energy.


The landscape is a unit of land distinguished by a natural boundary and having patches of the different ecosystem. Example of the landscape is the southern peninsula.


The biome is a complex of several types of communities maintained under more or less similar environment. In other words, the biome is a large regional unit delimited by a specific climatic zone, having a particular major vegetation zone and it’s associated funna.  tundra desert and ocean are examples of the biome.


The biosphere includes earth along with its atmosphere (air, water, and land) that sustain life.

More important terms used in Ecology

  • Biological Clock – It is an internal mechanism in the organisms that controls the periodicity of various functions or activities.
  • Ecotone It is a transition zone present between two different type of community. The species found in ecotone are called Edge species and the effect of these species on the other species is called Edge effect.