|Class 10 Biology Our Environment||Food chains|
A food chain is a series of organisms where all the organismsare dependent on next organism as a source of food.
The series of organism take part at various biotic levels to form a food chain.
Each step of the food chain forms a tropic level.
The producers (green plants) are at the first tropic level.
Primary consumers (herbivores) are at the second tropic level.
Secondary consumers (small carnivores) constitute the third tropic level.
Tertiary consumers (larger carnivores) form the fourth tropic level.
Producers have the greatest number of individuals
Fig. Various tropic levels
Example of food chain- i) Grass à insects àfrog à snake à eagle
Grass is eaten by insects and frogs eat the insects which in turn are eaten by the snakes and eagles eat the snakes.
Fig. Food chain
Flow of energy takes place from one component of the food chain to another.
ii) Sun --> plant --> dear --> lion
Fig. Food chain
The autotrophs capture 1% of energy present in sunlight and convert it into chemical energy, the chemical energy then flows to heterotrophs and decomposers.
When green plants are consumed by the primary consumers a great amount of energy is lost as heat to the environment and rest of the energy is used up by the body of consumers for digestion, growth, reproduction.
An average of 10% of food is turned into its own body which is again consumed by the secondary consumers.
At the fourth tropic level very less mount of usable energy remains as the energy which flows from one level to another is very little.Chemicals may enter our bodies through food chains.
Bio magnification is the process in which maximum concentration of chemicals get accumulated in the body organisms of fourth tropic level.
Pesticides used to protect the crop from pests are washed away in the water bodies or into the soil.
Plants and aquatic animals absorb the chemicals from soil and water bodies respectively which then accumulate in the body of tertiary consumers.
Human beings occupy the top tropic level hence maximum amount of chemicals accumulates in the body of human beings