Class 12 Biology - Chapter Ecosystem NCERT Solutions | Distinguish between (a) Grazing food cha

Grazing food chain

Detritus food chain

1.

In this food chain, energy is derived from the Sun.

1.

In this food chain, energy comes from organic matter (or detritus) generated in trophic levels of the grazing food chain.

2.

It begins with producers, present at the first trophic level. The plant biomass is then eaten by herbivores, which in turn are consumed by a variety of carnivores.

2.

It begins with detritus such as dead bodies of animals or fallen leaves, which are then eaten by decomposers or detritivores. These detritivores are in turn consumed by their predators.

3.

This food chain is usually large.

3.

It is usually smaller as compared to the grazing food chain.

Production

Decomposition

1.

It is the rate of producing organic matter (food) by producers.

2.

It is the process of breaking down of complex organic matter or biomass from the body of dead plants and animals with the help of decomposers into organic raw material such as CO₂, H₂O, and other nutrients.

2.

It depends on the photosynthetic capacity of the producers.

2.

It occurs with the help of decomposers.

3

Sunlight is required by plants for primary production.

3.

Sunlight is not required for decomposition by decomposers

Upright pyramid

Inverted pyramid

1.

The pyramid of energy is always upright.

1.

The pyramid of biomass and the pyramid of numbers can be inverted.

2.

In the upright pyramid, the number and biomass of organisms in the producer level of an ecosystem is the highest, which keeps on decreasing at each trophic level in a food chain.

2.

In an inverted pyramid, the number and biomass of organisms in the producer level of an ecosystem is the lowest, which keeps on increasing at each tropic level.

Food chain

Food web

1.

It is a single linear sequence of organisms.

1.

It contains a number of interconnected food chains.

2.

Members present at higher trophic levels feed on single types of organisms.

2.

One organism has alternate food sources.

Litter

Detritus

1.

Litter contains all kinds of wastes generated above the ground.

1.

Detritus is composed of the remains of dead plants and animals.

2.

Litter contains both biodegradable and non-biodegradable matter.

2.

Detritus contains only biodegradable matter.

Primary productivity

Secondary productivity

1.

It is defined as the amount of organic matter produced by producers per unit area over a period of time.

1.

It is defined as the rate of production of organic matter by consumers over a period of time.