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Energy flow of Ecosystem : Food Chain, Food Web, Ecological Pyramids

Energy flow of  Ecosystem : Food Chain, Food Web, Ecological Pyramids
Energy is defined as the capacity to do work. There are two types of energy 1.Potential and 2. Kinetic. Potential energy is the energy at rest and kinetic energy is the energy of motion.

Energy flow of  Ecosystem

 

Energy

 

Energy is defined as the capacity to do work. There are two types of energy 1.Potential and 2. Kinetic. Potential energy is the energy at rest and kinetic energy is the energy of motion. The source of energy required by all living organisms is obtained by the chemical energy of food. The chemical energy is obtained from the radiant energy of sun. In any ecosystem, there should be unidirectional flow of energy. The flow of energy is based on law of thermodynamics.

 

First Law of Thermodynamics

 

According to this law, the amount of energy in the universe is constant. The energy can neither be created nor be destroyed but may change from one form to another.

 

Second Law of thermodynamics

 

According to this law no energy transformation takes place spontaneously unless energy is degraded. The change of energy from one form to another takes place in such a way that a part of energy is dissipated in the form of heat. Energy flows from higher to lower level.

 

Energy Flow

 

When light energy falls on green plants, it is transformed into chemical energy and stored as organic products in plants. When the herbivores consume these plants, the chemical energy is transformed into kinetic energy. During this process degradation of energy will takes place by conversion into heat. The degradation continues when herbivores are consumed by carnivores.

Food Chain

 

In ecosystem, the biotic factors are linked together by food. For example, the producers form the food for the herbivores. The herbivores form the food for carnivores. 'A food chain can be defined as a group of organisms in which there is a transfer of food energy, through a series of repeated eating and being eaten'.

Producers - > Herbivores - > Carnivores.

The various steps in a food chain are called trophic levels.

Grass Land

Plants - > Mouse - > Snake - > Hawk.

Forest

Plants - > Goat - > Lion.

 

Energy flows through food chain. The transfer of energy from one trophic level to another is called energy flow.


Types of Food Chains

The food chains are of two types, namely

1.                Grazing food chain.

2.                Detritus food chain.

Grazing Food Chain

 

The grazing food chain starts from green plants and ends in carnivores. This type of food chain depends on the autotrophs, which capture the energy from solar radiation.

Food Chain in Terrestrial Ecosystem

 

The sequence of food chains in the terrestrial ecosystem may be represented as follows.

Grassland  ->  Rodents ->  Snakes  ->   Hawks.

(Crop plants)                    

Producer consumer -> Primary consumer ->Secondary consumer ->Tertiary consumer

 

Detritus Food Chain

 

The organisms which feed exclusively on the dead bodies of animals and plants are called Detrivores. It includes bacteria, fungi, protozoan etc. These organisms ingest and digest the dead organic materials and convert it into CO2 and water.

 

Food Web

 

In an ecosystem, the various food chains are inter-connected with each other to form a net work called Food Web. Simple food chain is very rare. So, each organism may obtain food from more than one trophic level.

1. Grass -> Grasshopper -> Garden Lizard     -> Hawk

2. Grass -> Grasshopper -> Hawk       

3. Grass -> Rabbit    -> Hawk    

4. Grass -> Mouse    -> Hawk    

5. Grass -> Mouse    -> Snake     -> Hawk

 

In grassland ecosystem, grasses eaten by grasshopper, rabbit and mouse. Grasshopper is eaten by garden lizard which is eaten by hawk. In addition hawk also directly eats grasshopper and mouse. Thus five lines are interconnected to form a food web. Food webs are very important in maintaining the stability of an ecosystem.

 


Ecological Pyramids

 

The number, biomass and energy of organisms gradually decrease from the producer to the consumer level. This can be represented by a pyramid called ecological pyramid. It is the graphic representation of the number, biomass and energy of the successive trophic level of an ecosystem. The use of ecological pyramid was first described by Charles Elton in 1927.

There are three types of ecological pyramids namely,

 

1. The pyramid of numbers,

 

2. The pyramid of biomass,

 

3. The pyramid of energy.


1. The Pyramid of Number

 

The number of individuals at the trophic level decrease from the producer to the consumer level. In croplands the crops are more in numbers. The grasshoppers feeding on crop plants are lesser in number, The frogs feeding on grasshopper are still lesser in number. The snakes feeding on frogs are fewer in number.

 

In a grassland the grasses are large in numbers. The consumers decrease in the following order.

 

Crops  - >  Grasshopper  - > Frogs  - > Snakes  - > Hawks.

 


2. The pyramid of biomass

 

Biomass refers to the total weight of living matter per unit area. In an ecosystem the biomass decreases from the producer level to the consumer level.

In a grassland the biomass of grasses is the maximum and it gradually decreases towards the consumer level.

Grass                               -> Grasshopper  -> Garden Lizard  -> Hawk.

Grass                               -> Mouse  ->      Snake  -> Hawk.

 

In a forest, the biomass of trees is the maximum and the top consumer is the minimum. The decrease in weight occurs in the following order.

Plants                              ->    Deer   ->     Fox   -> Tiger.

Plants                              ->    Rabbit  ->   Fox   -> Lion.


3. Pyramid of energy

 

In an ecosystem, the energy flow from the producer to the consumer level will be decreasing. In a grassland, grass plants trap the maximum sun light energy. The energy gradually decreases towards the top consumer level. The chemical energy is transformed into kinetic energy.

Grass                               -> Rabbit  -> Fox         -> Lion.

Grass                               -> Grasshopper  -> Garden Lizard  -> Hawk.

Grass                               -> Mouse  -> Snake     -> Hawk.


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