Ecology

Ecology is defined “as a scientific study of the relationship of the living organisms with each
other and with their environment.”
The term 'Ecology' was coined by the German zoologist, Ernst Hackle in 1866. Ernst
Haeckel used the term Oekologie instead of Ecology and explained it briefly. The word Oekologie is
formed by combining two Greek words Oikos (House or living space) and logos (Science or Study).

Ecosystem: In 1935, A.G Tansley proposed the concept of Ecosystem. According to him, Ecosystem
is type of a physical system formed by biotic and abiotic components. According to him, ecosystem
is an open system. These systems may differ in their size.
According to Odum ( 1963 ), ecosystem is the main active unit of ecology.
Characteristics of Ecosystem –
• It covers/occupies a definite area in the Biosphere.
• The ecosystem is a functional unit of nature.
• Ecosystem has its own productivity.
• Ecosystem is an open system where there are continuous input and output of energy and
substances

Types of Ecosystems
Ecosystem is of two major types
a) Natural ecosystem :
i) Terrestrial ecosystem ( for example - forest ecosystem, grassland ecosystem, desert
ecosystem ) and
ii) Aquatic ecosystem can be fresh water ecosystem and marine ecosystem. Fresh water
ecosystem may be lotic
(free flowing type, e.g. rivers) or lentic (standing type, e.g. ponds, lakes ).

b) Artificial or man-made ecosystem: These ecosystems are created by man. For example – cropland
ecosystem, fisheries etc.

✓ Ecosystems are capable of maintaining their state of equilibrium. They can regulate their own
species structure and functional processes. This capacity of ecosystem of self regulation is
known as homeostasis.

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 ✓ Lentic Ecosystem refers to the static water habitats like ponds, lakes, swamps and marshes.
✓ Lotic Ecosystem refers to the moving water habitats like rivers.

Components of Ecology

Biotic Component: The plants, animals and the micro-organisms present in an ecosystem form the
biotic component. Biotic components are the living beings things that shape an ecosystem. Depending
upon the different nutritional behaviour , biotic components may be divided into-
a) Autotrophs and b) Heterotrophs

a) Autotrophs : They are known as producers. They can produce their food themselves by making
use of carbon dioxide present in air and water in presence of sunlight by involving chlorophyll, the
green pigment present in leaves of plants, through the process of photosynthesis. There are some
micro-organisms which
can produce organic matter through oxidation of certain chemicals in absence of sunlight.
b) Heterotrophs : Organisms of this class can not produce their food by themselves. They get their
organic food from the producers. So they are called consumers. The consumers are of two types –
macro consumers and micro consumers.
Macro consumers : The animals that consume the producers either directly or indirectly are called
macro consumers. These can be divided into four types
i) Herbivores: Animals that directly consume producers are called herbivores or primary
consumers. Examples – cows,deer, goat etc.
ii) Carnivores: They feed on other consumers. If they feed on herbivores, they are called
secondary consumers. Examples frog. If they feed on other carnivores, then they are known as tertiary
consumers. Example – snake, big fish.
iii) Omnivores: They feed on both plants and animals. Example – man, fox, rat etc.
iv) Detrivores : They generally feed on the dead animals, partially decomposed matter, wastes
of other living organisms. Examples –beetle, ants, earthworms etc.
Micro consumers : There are certain living organisms that derive their nutrients by decomposing or
breaking down dead plants and biotic compounds in the environment. They are called decomposers or
micro consumers. Examples – bacteria, fungus.

Difference between Producer and Consumer

Producer Consumer
Producers are organisms that make their own Consumers are incapable of producing their own
food. food
They are autotrophs They are heterotrophs.
They play a primary role in the food chain. They play a secondary role in the food chain.
They occupy the first trophic level in the food They do not occupy the first trophic level rather
chain. occupy other trophic levels.

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Abiotic Components: The physical and chemical components of an ecosystem constitute the abiotic
structure. It includes all kinds of physical factors like sunlight, latitude and longitudes, average
temperature, rainfall pattern, wind velocity etc. as well as edaphic ( soil ) factors. Under chemical
components, major nutrients like carbon, nitrogen, phosphorous, oxygen, potassium etc, compounds
like carbohydrates, proteins, nucleic acid, various other organic matters present in soil and water
influence the functioning of the ecosystem.

Function of an ecosystem: The major functional characteristics of an ecosystem may be described in

terms of food chain, food webs and trophic levels, energy flow, nutrient cycles etc.

Food Web or Food Chain:

In an ecosystem, the sequential chain of eating and being eaten is called a food chain. Food chain
depicts the flow of energy through different organisms in an ecosystem. Notably, this flow is
unidirectional. A food chain starts with producers and ends with top carnivores. The common
examples of food chain are–
Grasses –cattle – tiger ( the chain consists of three links )
Grasses – grasshopper – birds – hawks ( the chain consists of four links )
Phytoplankton – water fleas – small fish – tuna

Types of Food Chains:

i) Grazing food chain: The consumers which start the food chain, utilising the plant or plant
part as their food, constitute the grazing food chain. This food chain begins from green
plants at the base and the primary consumer is herbivore.

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 ii) Detritus food chain: It starts from dead organic matter of decaying animals and plant
bodies consumed by the micro-organisms and then to detritus feeding organism
called detrivores or decomposer and to other predators.

The distinction between these two food chains is the source of energy for the first level consumers.

Food web
A number of food chains interwoven with one another give rise to a structure similar to the web of
a spider. These interlocking patterns formed by several food chains that are linked together are
called food webs. So food web is a network of food chains where different types of organisms are
connected at different trophic levels, so that there are a number of options of eating and being eaten
at each trophic level. The food web provides more than one alternative for food to most of the
organisms in an ecosystem and therefore increases their chance of survival.

Trophic level
Every organism in an ecosystem can be assigned a feeding level, referred to as the trophic level. The
living organisms which derive energy from the same source are said to belong to the same trophic
level. Thus the green plants would be grouped in the first trophic level (producers), herbivores in the
second trophic level(primary consumers), carnivores in the third (secondary consumers), and so on.

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Ecological Pyramids: The concepts of Ecological Pyramid was Developed by Charles Elton.

The graphical representation of the trophic structure and functions of an ecosystem with
producers at the base and successive trophic levels of consumers forming the higher layers is known
as ecological pyramids.
There are three types of Ecological Pyramids:
i) Pyramid of Energy: The pyramid of energy is by far the most practical of all the three
ecological pyramids as it depicts the actual functional relationships between trophic
levels. It represents the amount of energy present at each trophic level. Likewise it starts
with the producers and ends with consumers at higher trophic levels. It is also called as
pyramid of productivity
ii) Pyramid of Number: Pyramid of numbers may be defined as graphical representation
of number of individual organisms per unit area at each trophic level arranged stepwise
with producers at the base and top carnivores at the top.
iii) Pyramid of Biomass: A pyramid of biomass shows the relationship between biomass
and trophic level by quantifying the biomass present at each trophic level at a particular
time. It is a graphical representation of biomass (total amount of living organic matter
in an ecosystem) present in unit area at a particular time in different tropic levels. The
pyramid of biomass may be upright or inverted.

PREVIOUS YEAR QUESTIONS Year

1. Tiger is ______ level consumer of an Ecosystem. 2021,2022

2 Fog is _______ level consumer of Ecosystem 2020, 2022
3 ______is one type of Omnivorous animal. 2023
4 Write the difference between Autotrophs and Heterotrophs 2023,2019
5 What is Ecosystem? Write a brief note on Natural Ecosystem. 2023
6. Write Short Notes on Food Chain and Ecosystem? 2022
7. What is Food Web? 2022
8. Give an Example of lotic ecosystem? 2022
9. Define and distinguish between Producer and Consumer? 2022,2021
10 Write a short note on Food Chain? 2021,2019
11. Write a short note on Food Web? 2020
12. Define and distinguish between Decomposer and Consumer? 2019
13. Every food Chain starts with a______ 2019
14. Write a short note on Abiotic Component of Environment? 2019
15. Define and Distinguish between Population and Community. 2019

16. Which one of the following is the largest ecosystem of the world?
(a) Ocean (b) Grassland
(c) Forest (d) Mountains

17. Which of the following is not correct about the ecosystem?

(a) It comprises both, abiotic and biotic components
(b) It has its productivity.

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 (c) It is a closed system.
(d) It is a natural resource system.
18. The term Ecosystem was proposed by –
(a) G. Tailor (b) E. Hartigan
(c) D.R. Stoddart (d) Tansley

19. The highest trophic level in an ecosystem is obtained by:

(a) Herbivores (b) Carnivores
(c) Omnivores (d) Decomposers
20. The primary source of energy in Eco-body is –
(a) Energy emitted by fermentation
(b) Preserved vegetable sugar
(c) Solar energy
(d) None of the above.
21. In a food chain, man is:
(a) producer
(b) only primary consumer
(c) only secondary consumer
(d) primary as well as a secondary consumer
22. Trophic level-I includes –
(a) Herbivorous animals (b) Carnivorous animals
(c) Omnivorous animals (d) Green plants
23. In the marine environment, the main primary producers are:
(a) Phytoplanktons (b) Seaweeds
(c) Marine angiosperms (d) Aquatic bryophytes