The document discusses the structural and functional components of ecosystems, emphasizing the interaction of biotic and abiotic elements. It covers the classification of organisms into autotrophs, heterotrophs, and decomposers, and explains the significance of food chains and food webs in energy flow and nutrient cycling. A case study on bio-magnification of DDT illustrates the accumulation of toxins through trophic levels, highlighting environmental concerns.

1. Components of an
Ecosystem
20MNT31
&
Environmental Science
Presented by
Mrs.K.Krishnaveni
Assistant Professor
Department of Chemistry
Kongu Engineering College
Perundurai, Erode

2. Ecosystems:
Concept and components of an ecosystem -structural and functional
features – Functional attributes (Food chain and Food web only).
Biodiversity:
Introduction – Classification – Bio-geographical classification of India-
Value of biodiversity – Threats and Conservation of biodiversity - case studies.

3. Ecosystems
 A self-regulating group of biotic communities of species interacting with one
another and with their non-living environment exchanging energy and matter.
 Study of the ecosystems is often known as - Ecology
 Ecosystems consists of interacting plants, animals and microorganisms as well as
non-living components (soil, water, O2 etc,.)
 Life on the earth is sustained by the flow of energy from the sun and cycling of
nutrients through the ecosystems

4. Structural and Functional Components of Ecosystems
Each ecosystem comprises of two basic components
1. Abiotic Components 2. Biotic components

5. Abiotic Components or Non-living components
 These include the non-living, physico-chemical factors such as air, water, soil, elements
and compounds of the environment. It is broadly classified as
1. Climatic factors- which include the climatic regime and physical factors of the
environment like sunlight, humidity, temperature, wind, rainfall,
water, etc.,
2. Edapic factors - which are related to the structure and composition of soil such as
minerals, soil organisms, organic substances, etc.,
Biotic Components or Living components
 It comprises the living part of the environment (like plants & animals) which is made
up of many different inter-dependent organisms. Biotic components are distinguished
into autotrophs, heterotrophs, saprotrophs.

6. I. Autotrophs or producers – which can synthesize their food
themselves from compounds that are obtained from their environment.
 Photoautotrophs – mainly green plants uses light as energy
source and synthesize their food themselves through the process of
photosynthesis.

7.  Chemo-autotrophs: chemo-autotrophs are microorganisms which can
produce food to some extent through oxidation of certain chemicals in
the absence of sunlight.
 Ex. Chemoautotropic sulphur bacteria make use of the heat generated
by the decay of radioactive elements (present in the earth’s core and
released in ocean’s depths). They use this heat to convert dissolved H2S
and CO2 into organic food sources.

8. II. Heterotrophs or Consumers:
They mainly depend on the producers for their food.
They are further classified as
1.Herbivores or primary consumers
2.Carnivores or Meat eaters
3.Omnivores
1.Herbivores or primary consumers:
They directly feed on producers. Eg. insects, rabbit.
2.Carnivores or Meat eaters: They feed on other animals for their food
 Primary carnivores or secondary consumers:
They take food from herbivorous animals. Eg. Fox
 Secondary carnivores or tertiary consumers:
They take food from primary carnivores. Eg.Wolf

9. Tertiary carnivores or quaternary consumers:
They take food from other carnivores. Eg.lion.
3.Omnivores: They take food from both plants and animals.
Eg. Birds, humans, rat
4.Detritivores: They feed on dead organisms.
Eg. beetles, vultures, ants, termites
III. Saprotrophs or Decomposers
They derive their nutrition by breaking down the complex
organic molecules to simple organic compounds and ultimately
into inorganic nutrients. Eg. Bacteria, fungi
In few ecosystem, biotic structure prevails eg. Forest, while in others
decomposers predominates
Eg. Deep ocean

10. Functions of Ecosystems
 Each ecosystem functions systematically under natural conditions.
 It receives energy from sun and transfers it through various biotic and abiotic
components.
 All life on earth depends upon this flow of energy. Besides energy, various nutrients
and water also exchanged within the biotic and abiotic community.
 Tropic levels (or) Feeding levels
 The various steps through which food energy passes in an ecosystem is
called as Tropic level.
1st Trophic Level: Producer, 2nd Trophic Level: Primary Consumer
3rd Trophic Level: Secondary Consumer 4th Trophic Level: Tertiary Consumer
 The transfer of energy and nutrient occurs in the following ways
1.Food Chain
2.Food Web

11. 1. Food Chain : Sequence of eating and being eaten in an ecosystem
 All organisms, living or dead, are potential food for some other organisms.
Food chains in ecosystems are rarely found to function as isolated linear sequences.
They are found to be interconnected and usually form a complex network with several
linkages known as food web.

12. 2. Food Web : Interlocking pattern of various food chains of an ecosystem
 Food web is a network of food chains where different organisms are connected at
different tropic levels, so that there are a number of options of eating and being
eaten at each tropic level.

13. Nature has evolved food webs in ecosystems instead of simple linear food chains
Because food webs give greater stability to the ecosystem.
In linear food chain, if one species becomes
extinct then the species in subsequent
tropic levels are also affected.
In food web there are a number of options
available at each tropic level. So if one species
Is affected, it does not affect other tropic levels.

14. Significance of food chains and food webs
1. Energy flow and nutrient recycling takes place through them
2. Regulates population size of organisms and maintain ecological balance
3. Food chains show a unique property of biological magnification of some
chemicals.
Non-biodegradable chemicals are not decomposed by microorganisms
and they keep on passing from one tropic level to another. At each successive
tropic level, concentration of chemical increasing. This phenomenon is known
as biological magnification

15. Case Study
Bio-magnification of DDT
Bio-magnification happens when toxic chemicals, like DDT, whose remains in
the environment are consumed indirectly by organisms through food. When an
organism in the higher food chain consumes the lower organism containing such
chemicals, the chemicals can get accumulated in the higher organism. In other words, it
travels through the food chain harming every single stratum. The concentration of these
toxins or chemicals increases through the trophic levels of the food chain.
Moreover, because of its non-biodegradable character, it can remain in soil or water for
many years leading to a very dangerous and concerning process – bio-magnification.

17. 12-Oct-23