Learning Outcomes

the end of this Lecture, students will be able to

• Explain Ecology

• Discuss structure and function of

• Elaborate components of ecosystem


• Introduction: Ecology- Objectives and

• 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”.

Used in Ecology

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

A group of similar or dis-similar
species species living to gather under more or less similar environmental

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

The complex of several type of community, at
different stages of succession living to gather under similar environmental

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

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

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


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

Plant Ecology

Animal Ecology

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:

It is also known as ecology of
individual organisms.

It is also known as ecology of groups
of organisms.

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

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

of an Ecosystem

• Each organisms has two main components

      1. Abiotic

      2. Biotic

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

• Abiotic component are mainly of two

(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

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.

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:

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

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

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

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.

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