food chain and ecological energetics

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ASSIGNMENT ON ECOLOGY
ECOLOGICAL ENERGETICS AND FOOD CHAIN
Submitted To:
Sir AZAD ALI MIRZA
Submitted By:
ATIKA NOOR
Swot Degree CollegeLiaquat Pur.

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ACKNOWLEDGEMENT
The price of victory is high but so are the
rewards. None of us got to where we are alone. Whether the
assistance we received was obvious or subtle, acknowledging
someone's help is a big part of understanding the importance of
saying thank you.
I’m indebted to acknowledge the efforts of my Botany teacher,
Sir Azad Ali Mirza.
And to my Swot Degree College without whom I would not be
able to build my courage and to prepare such an excellent
assignment.
Atika Noor.

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Dedication:
Loyalty and dedication can't be bought or
paid to go away.
I dedicate my achievement to “Sir Azad Ali Mirza”
With words,
“A teacher affects eternity;
He can never tell where his influence stops.”
To my parents “who always picked me up on time and
encouraged me to go on every adventure, specially this one.”
Atika Noor

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Ecological Energetic & Food Chain
 Ecological Energetic.
 Food Chain.
Definition.
Explanation.
Links.
Laws of thermodynamics.
 1st
law of thermodynamics.
 2nd
law of thermodynamics.
Components of food chain.
1) Producers.
2) Consumers.
Trophic levels in food chain.
 1st
Trophic level.
 2nd
Trophic level.
 3rd
Trophic level.
 4th
Trophic level.
Energy flow in food chain.
Examples of food chain.
Types of food chain.
1) Grazing food chain.
2) Detritus food chain.
3) Supplementary food chain.
Application or Advantages of food chain.

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EcologicalEnergetics & Food Chain.
Ecological Energetics:
All the organisms living in ecosystem interact
with one another. They obtain food from many sources.
Environment produces food for every organism to survive, to
flow of cycles.
A roadrunner chases a lizard. The lizard
races behind a cactus and dives to safety in a crack in a rock.
From where does energy come out for chasing?
Thus, it comes from the food eaten by them and this helps to
perform their living activities. The flow of energy in ecosystem
involve ecological energetics.
FOOD CHAIN:
Definition:
“The step wise process of eating and being eaten,
among the organisms for the flow of energy is called food
chain.”
Explanation:
 In an ecosystem , food is very necessary for life. It is
provided by many means. The main purpose to obtain
food is to get energy.
 The main source of energy in the universe is the sun.
Plants capture the sunlight and used it to prepare food.
Consumers eat plants and get food thus a chain is formed
of eating and being eaten is formed which also explains
the flow of energy from a trophic level to other.
 Food chain starts from the plants and ends on the
carnivores or top predators. Herbivores eats plants and

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carnivores eat herbivores .carnivores are eaten by top
predators which on death are decomposed by
decomposers thus a food chain is formed.
Links:
The feeding relationship between organisms is shown
by links or arrows. This is called links. In a simple food
chain 3 to 5links are present.
Laws of thermodynamics:
Food chain is usually followed by laws of thermodynamics
there are two laws of thermodynamics.
 1st
law of thermodynamics:
This law states that ,
“Energy is neither destroyed
nor created but it is changed from one form of energy
to another.”
According to this law, plants conserve sun light energy in the
form of carbohydrates and is eaten by heterotrophic organisms
which made this obtained energy the part of the organic matter
of their body. When the organisms die the decomposers
decompose the food and release the energy from the organic
matter of the organism. Thus the released energy is equal to
the energy utilized to form that organic matter.
 2nd
law of thermodynamics:
This law states,
“Energy obtained is utilized to do
work.”
producers herbivores carnivores Top predators decomposers

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Thus organisms use this energy and play their daily
roles in life.
Components of food chain:
A food chain mainly comprises of following
components.
1) Producers.
2) Consumers.
 Producers:
Producers are the autotrophs which capture the
sunlight and prepare food (carbohydrates) using CO2.
In terrestrial ecosystem producers are plants which may be
herbs, shrubs and trees.
 Consumers:
Consumers are the hetrotrophs which cannot
prepare their own food. They are further divided into
following categories.
 Primary consumers:
These are herbivores and feed on plants.
e.g. grasshopper, cow, goat etc.
 Secondary consumers:
Secondary consumers feed on primary
consumers. They are carnivores.
e.g. Rat.
 Tertiary consumers:
Tertiary consumers feed on secondary
consumers.
e.g. Snakes.

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 Quaternary consumers:
This type of consumers feed on tertiary consumers.
e.g. Eagle, owl.
 Top Predators:
This type of consumers have usually no
predator. They feed on quaternary and tertiary
consumers.
e.g. Hawk, Shark.
Trophic levels in Food Chain:
Trophic level is derived from the Greek word
“trophikos” means “feeding” or “nutrition”.
The main trophic levels are described below.
First trophic level includes producers and is
represented by T1.
Second trophic level includes the herbivores and is
denoted by T2.
Third trophic lllevel includes carnivores and is
represented by T3.
Fourth trophic level consists of tertiary consumers
or top predators and is denoted by T4.
Fig; “Diagrammatic representation of trophic levels.”

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 Energy flow in Food Chain:
The main source of energy on earth is
the sun. 90 % of the sun energy goes to the
atmosphere and only 10% of energy is captured and
used by plants to prepare their food.
Herbivores eat the plants and utilized the energy
stored by plants but with 10% loss.
10% energy is again lost and go to the next trophic
level i.e. to the secondary consumers and so on.
Fig; “Energy flow through food chain.”
At each level 10%loss occurs, thus there is
necessary to discuss the chain length.2-3 links
present are more significant for the energy flow.
But 3-5 links are not suitable significantly because
at tertiary level very low energy is available to
organism to use due to loss of energy at each level.

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 Examples of Food Chain:
There are different food chains in
different ecosystems or biomes.
In grass land ecosystem:
Grass Grasshopper Toad
Eagle Snake
Grass Cow Lion
In forest ecosystem:
1) Herbs or Shrubs Rabbit Snake
Eagle
2)
In aquatic ecosystem:
Phytoplankton zooplankton Frog larvae
Shark Fish Fish larvae

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In terrestrial ecosystem:
Trees Goat Tiger
Trees Man Decomposers
Lichens Slug or Snail Toad
Hawk Snake
 Types of Food Chain:
Three types of food chain are present.
1) Grazing food chain.
2) Detritus food chain.
3) Supplementary food chain.
 Grazing Food Chain:
The grazing food chain starts from a green
plant(producer) base; goes to grazing herbivore represented by
cattle grazing in pastureland, deer browsing in the forest, rabbit
feeding in old fields and insect pests feeding on garden crops;
and on to carnivores. A grazing food chain is not the major food
chain in the terrestrial and many aquatic ecosystem. Only in
deep-water aquatic system with low biomass ,rapid turnover of
organisms and high rate of harvest.
Grazing food chains play dominant role in energy flow. In
terrestrial ecosystem a small portion of primary production goes
by the of grazing food chain. For example in a yellow forest
only 2.6 percent of net primary production was utilized by
grazing herbivores over a period of three years.

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Fig; “Grazing food chain.”
Generally the energy transformed through the ecosystem by
way of grazing chain is reduced by a magnitude of 10 at each
trophic level. Due to loss of energy at each trophic level the
amount of energy available for third and fourth trophic level
carnivores that a few organisms could be survived if they
depended on that source alone.
 Detritus Food Chain:
Dead organic matter present on the
surface of earth is called detritus. Decomposers are called
detrivores because they feed on the detritus. Detritus food
chain goes from dead organic matter into microorganisms
and then to detritus feeding.
Fig; “Detritus food chain.”

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The detritus food chain is common to all ecosystems but is
the major pathway of energy flow in the terrestrial
ecosystem.
For example in yellow poplar forest ,50 % of gross primary
production goes into maintenance and respiration,13 % is
accumulated as new tissue, 2% is consumed by
herbivores and 35% goes to the detritus food chain.
Fig; “An example of Detritus food chain.”
A good example of detritus food chain is one based on
mangrove leaves which fall into warm shallow water.
These fragments are acted on by saprotrophs(fungi,
bacteria and protozoa)and colonized by algae. A group of
small detritus consumers (mollusks, nematodes, insect larvae
crabs, amphipods, grass shrimps, sheephead, minnow etc)feed
upon these leaf fragments and organic matter pass
through the guts of these detritus consumers repeatedly.
Detritus consumers act as food for smaller and larger game
fish, herons, stocks, fish-eating birds(carnivores).
 Supplementary Food Chain:
Other feeding groups such
as parasites and scavengers, for supplementary food
chain in community.
Fig; “Supplementary food chain.”

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Parasitic food chain operates in many ecosystems,
however food energy passing through these chains is not
considerable. They are highly complicated because of life
cycles of parasites. Some parasites are passed through
one host to another by predators in the food chain.
Ectoparasites may move from one host to another through
plant fluids.
Advantages of Food Chain:
 Food chains in different ecosystems describe
pathway of energy flow.
 Food chain studies help to understand the feeding
relationship and the interaction between the
organisms.
 They also help us to comprehend the energy flow
mechanism.
 Material circulation in ecosystems, and
understanding the movement of toxic materials in the
ecosystem can be determined with the help of food
chain.

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References:
 Text book of Ecology for B.Sc.
 Notes on Food Chain by “Sir Azad Ali Mirza.”
 “A Tundra Food Chain” By Rebecca Hogue Wojahn.
 “Food Chains in a Desert Habitat” By Isaac Nadeau.
 “Erwin Schrödinger’s World View.”
 “Systems Theory Applied to Agriculture and the Food Chain”
edited by J.G.W. Jones, P.R. Street.

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