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PinkMonkey Online Study Guide-Biology

CHAPTER 25 : THE ECOLOGY AND THE ENVIRONMENT

25.0 Introduction

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 otherís 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.

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Table of Contents


25.0 Introduction
25.1 Species

Chapter 1




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