GE8291 CHAPTER2 FOOD CHAIN AND FOOD WEB

GE8291 CHAPTER2 FOOD CHAIN AND FOOD WEB

 

FOOD CHAIN:

The sequence of eating and being eaten in an ecosystem is called as  food chain. It can also be defined as the transfer of food energy from the plants through a series of organisms in various trophic levels.

Note: At  each and every transfer nearly 80-90% of potential energy gets lost as heat and a food chain always starts with plant life and ends with animal.

examples: Food chain in Grassland:

Plants ——-> Rat——>Snakes——–> Eagles

Here,Plants are Producers , Rat is Primary consumer , Snake is Secondary consumer and Eagle is Tertiary consumer.

Types Of Food Chain and Energy Flow:

Food  chains are classified  into two main types:

1. Grazing food chain

2. Detritus food chain

Grazing food chain:

It is  found in Grassland ecosystem and Pond ecosystem.Grazing food chain starts with green plants and goes to decomposer food chain or detritus food chain through herbivores and carnivores.

Detritus food chain:

It is found in Grassland ecosystem and Forest ecosystems.Detritus food chain starts with dead organic matter such as plants and animals and goes to  decomposer food chain through herbivores and carnivores.

Note: Trophic levels are  the various steps through which food energy passes in an ecosystem.

FOOD WEB:

The interlocking pattern of the various food chain in an ecosystem is known as food web. here different types of organisms are connected  at different trophic levels so that there is  number of opportunities of eating  and being eaten at each trophic levels.

Difference between food chain and food web:

*In food chain if one species gets affected  or if it becomes extinct then the species in subsequent trophic levels are also affected.

*In a food web if one species gets affected it doesn’t affect other the other trophic levels so seriously. There are number of options available at each trophic levels.

Significance   of food  chain and food web:

1. Food chain and food web plays an important role in  an ecosystem.Energy flow and nutrient cycling takes place through them.

2. Maintain and regulates the population size  of different trophic levels and thus it  helps in maintaining ecological balance.

3.They have the property of biomagnification.

NoteBiomagnification:  The Non-biodegradable materials keep on passing from one trophic level to another. At each successive trophic levels the concentration keeps on increasing .  This process is called as biomagnification.

Eg:  DDT which is sprayed for pest control its concentration gets increased along with food chain through  phytoplankton to zooplankton and then goes to fish, birds, animals and human beings. Thus, the concentration of DDT  is magnified  thousands times in birds and humans which can damage egg shells of birds , cells of human being. since DDT is  fat soluble it cannot be easily removed from the human body.

 

 

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