Ecological Energetics & Food Chain.

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ASSIGNMENT ON ECOLOGY

ECOLOGICAL ENERGETICS AND FOOD CHAIN

Submitted To:

Sir AZAD ALI MIRZA

Submitted By:

ATIKA NOOR

Swot Degree College Liaquat Pur.

Ecological Energetics & Food Chain.

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Ecological Energetics & Food Chain.

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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

Ecological Energetics & Food Chain.

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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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Ecological Energetics & 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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