Living organisms are closely dependent upon the
living and non-living . No organism is totally independent of its
environment, and there is no environment which is not influenced
by the organisms it supports. In other words, organisms things and
their environments are interdependent and influence each other.
Environmental Factors
The multitude of things present in the environment
which influence the life of all organisms constitute environmental
or ecological factors which are of two types :
a) Abiotic factors, which include all
non-living things like light, air, water, temperature, minerals,
soil and climatic aspects.
b) Biotic factors, which include all
living organisms like plants, animals and microbes operating directly
or indirectly to influence the lives of each other.
These ecological factors not only determine the
types of animals and plants that survive in a particular region
but are also instrumental to building associations between animals
and plants.
A. Interaction between biotic factors
The activities of organisms influencing each other’s
lives, constitute biotic factors. These include interactions between
the biotic components like producers, herbivores, carnivores and
decomposers. These interactions are mainly of two types :
(a) Intraspecific biotic factors : These
are the interactions between the organisms of the same species.
Some of the significant ones are as follows:
i. Competition among animals of the same species
for food, shelter and mate.
ii. Competition among plants of the same species
for light, water and space.
iii. Interaction among the animals of social organizations
such as flocks, herds, shoals
iv. (groups of fish), loose colonies
of social insects, etc.
Fig. 25.1 Interaction between biotic and abiotic
factors
(b) Interspecific biotic factors: These
are the interactions between the organisms belonging to two
or more different species. Some of the significant ones are as follows
:
i. Predator and prey relationships.
ii. Different associations like parasitism,
commensalism, and mutualism.
iii. Reciprocal relationships between plants
and animals for food, pollination and dispersal of fruits
and seeds.
B. Interaction between biotic and abiotic factors
The biotic factors of environments like producers,
herbivores, carnivores and decomposers interact with abiotic factors
like light, water, air, soil and minerals.
Autotrophs like plants depend on abiotic factors
like light, carbon dioxide, water and minerals to prepare food by
photosynthesis. Herbivores feed on plants and carnivores depend
on herbivores for food. When these organisms die, the microorganisms
or decomposers in the soil break down the complex organic substances
into simple ones, and make them available to the producers..
Thus, abiotic as well as biotic factors maintain
harmony on the principle of "give and take" to maintain
equilibrium and to establish stable and self-regulating ecosystems.
