Intended Learning Outcomes

At the end of this Lecture, students will be able to

• Explain Ecology

• Discuss structure and function of ecosystem

• Elaborate components of ecosystem


• Introduction: Ecology- Objectives and Classification

• Concepts of an ecosystem- structure & function of ecosystem

• Components of ecosystem- Producers, Consumers, Decomposers


• Definition:- Ecology is derived from two Greek words “Oikos” & “Logos”

• Ecology= Oikos + Logos

       Oikos means house or dwelling place

       Logos means study of

Thus Ecology can be define as “Study of organisms with respect to their house or dwelling place”.

Terminology Used in Ecology

• Species: A Uniform interbreeding population spreading over time & space is known as species.

• Community: A group of similar or dis-similar species species living to gather under more or less similar environmental condition.

• Population: It is a group of similar community living together under similar environmental condition.

• Biome: The complex of several type of community, at different stages of succession living to gather under similar environmental condition.

• Vegetation: A collective growth of plants in space is known as vegetation.

• Habitat: The place where an organism live or the place where one would go to find a particular organism is known as habitat.

• Factor: Any external force, substance, or condition that affects the organism in any way is known as factor.

• Standing state: The total amount of inorganic substances i.e. minerals Such as phosphorous, sulfur, nitrogen, hydrogen, etc. present at any given time in the environment of an ecosystem is known as standing state.

• Biomass: Biomass is the total amount of living material present in terms of weight/ unit area.


Classification of Ecology

Ecology can be classified based upon its sub divisions as:

In early days of Ecology, botanist and zoologists engaged themselves in the study of ecology of plants & animals respectively this led to the development of such sub- divisions as

a) Plant Ecology

b) Animal Ecology

Based on Habitat Ecology: Some ecologist thought of the study of habitats and their effect upon the organisms. They selected a number of different habitat such as fresh water, grass land, forest etc.  This are then studied in detail for their possible relationship with the kind of organisms present there such an approach led to the development of habitat ecology.

• Based on level of Organization:- In this approach the organisms involved in ecology are either studied individually or in group accordingly they are classified as

         1. Autecology

         2. Synecology:

• Autecology: It is also known as ecology of individual organisms.

• Synecology: It is also known as ecology of groups of organisms.

Structure of Ecosystem

• A structure of Ecosystem comprise of

• The Composition of biological community including, species number, biomass, life history, and distribution in space.

• The quantity and distribution of non-living material, such as nutrient water, etc.

• The range of condition for existence such as, temperature, light etc.

Function of Ecosystem

Function of Ecosystem includes:

• The rate of biological energy flow i.e. production & respiration rates of the community.

• The rate of material or nutrient cycles

• Biological or ecological regulation including both regulation of organism by environment and regulation of environment by the organisms

Components of an Ecosystem

• Each organisms has two main components

      1. Abiotic

      2. Biotic

• Abiotic Component: The non-living factor or the physical environment prevailing in an ecosystem forms the abiotic components.

• Abiotic component are mainly of two types,

(a) Climatic factors It includes, rain, temperature, light, wind, humidity, etc.

(b) Edaphic factors (i.e. factors related to soil): It includes soil, pH, topography, minerals.

• Biotic Components: The living organisms include, plants, animals, and micro-organisms in an ecosystem forms biotic components.

• Biotic Components are further classified into 3 main groups

       1. Producers

       2. Consumers

       3. Decomposers or Reducers

Producer: The green plants have chrophyll with the help of which they trap solar energy and change it into chemical energy of carbohydrates using simple inorganic compound namely, water and carbon dioxide. This process is known as photosynthesis.

The chemical energy stored by the producers is utilized partly by the producers for their own growth and survival and the remaining is stored in the plants for their future use.

• Consumers: The animals lack chrophyll and are unable to synthesis their own food therefore they depend on the producers for their food.

• They are known as heterotrophs (i.e. heteros= others, trophs= feeder)

• The Consumers are of 4 types:

(a) Primary Consumer: (Herbivores) i.e. Animal feeding on plants, e.g. Rabbit, deer, goat etc.

(b) Secondary Consumers: The animal feeding on Herbivores are called as secondary consumers or primary carnivores. e.g. Cats, foxes, snakes.

(c) Tertiary Consumers: These are large carnivores which feed on secondary consumers. e.g. Wolves

(d) Quaternary Consumers: They are also called omnivores these are largest carnivores which feed on tertiary consumers and are not eaten up by any other animals. e.g. lion and Tiger.

Decomposers: Bacteria & fungi belong to this category.

• They break down the dead organic matter of producers & consumers for their food and release to the environment the simple inorganic and organic substance. These simple substances are reused by the producers resulting in a cyclic exchange of material between biotic & abiotic environment.


• Ecology can be defined as Study of organisms with respect to their house or dwelling place

• Ecology can be classified:

a) Plant Ecology

b) Animal Ecology

• Based on level of Organization:

a) Autecology

b) Synecology

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