.
Topic:
 Objectives
 Food chain
 Components
 Types
 Food web
 Types
 Comparison
 Significance
 Energy pyramid
Objective of Food chain and Food Web
 The various components of ecosystem constitute an interacting
system. They are connected by nutrients, minerals and energy.
These all circulate and recirculate between biotic and abiotic
components of ecosystem.
 Whereas, the flow of energy is one way, once used by the
ecosystem it is lost.Thus the continuous survival of ecosystem
depends upon the circulation and recirculation of nutrients and
energy.
Food Chain
 The sequence of transfer of matter and energy in the form of
food from organism to organism is termed as Food Chain.
 A food chain shows how the organisms are related with each
other by the food they eat and energy they transfered.
Components of a food chain
 There are four basic components of a food chain .
Sun
How a food chain Starts?
 All food chains generally starts with a Producers.
 Producers include plants that can make their own food.
 Then the food prepared by producers is consumed py consumers and then by
decomposers.
Tropic levels in a food chain
 It is the position an organism occupies in a food chain. Each link in a chain
represents one tropic level.
a) Producers
b) Consumers
Primary consumers (herbivores)
Secondary consumers (small carnivores)
Tertiary consumers (large carnivores)
Quaternary consumers
c) Decomposers
Produce own food.
Rely on producers for food.
Rely on dead organic
matter for food.
Cont...
Level 4
Level 3
Level 2
Level 1
Types of food chain
(a) Grazing or Predator Food Chain:
This food chain starts from green plants (producers), passes through the herbivore
(primary consumers) and ends with carnivore (secondary or tertiary consumers).
E.g. of grassland ecosystem
Grass→Rabbit→Fox→Wolf→Tiger
Cont...
(b) Saprophytic or Detritus Food chain:
• This type of food chain starts from dead organic matter of decaying animals and
plant bodies to the micro-organisms and then to detritus feeding organism and to
other predators.
• The organism of the food chain includes algae, bacteria, fungi, protozoa,
insects,nematodes etc.
Trees→ Fruit eating birds→ Lice and bugs→ Bacteria and fungi
FOOD WEB
 Food web can be defined as, "a network of
food chains which are interconnected at
various tropic levels, so as to form a
number of feeding connections amongst
different organisms of a community".
Examples of food webs
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•
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Soil food web
Aquatic food web
Forest food web
Grassland food web
Terrestrial food web
Cont...
• Example : Forest Food Web
Types of food web representation
Food Chain vs Food Web
Significance of Food chain and Food Web
• They help in maintaining the ecological balance.
• They help in understanding the feeding relations among organisms.
• Energy flow and nutrient cycling take place through them.
Energy Pyramid
 An energy pyramid is a graphical
representation, showing the flow of
energy at each trophic level in an
ecosystem.
 The width of each bar represents the
units of energy available within each
trophic level.
References
 Webb, P., & Boltt, G. (1990). Food chain to food web: a natural
progression?. Journal of Biological Education, 24(3), 187-190.
 Pimm, S. L. (1982). Food webs. In Food webs (pp. 1-11). Springer,
Dordrecht.
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