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Question
"Energy flow in food chains is always unidirectional". Justify this statement. Explain how the pesticides enter a food chain and subsequently get into our body.
Solution
The producers convert solar energy into chemical energy in the form of organic compounds. The primary consumers (herbivores) derive their nutrition from the producers. According to the energy transfer law, only 10% of energy is transferred from one trophic level to the other. So, the energy that is consumed by the producers does not revert back to the Sun and the energy transferred to the herbivores does not come back to the producers. It keeps on moving to the next trophic level in a unidirectional way. Hence, the flow of energy in the food chain is always unidirectional.
A large number of pesticides and chemicals are used to protect the crops from pests and diseases. Some of these chemicals are washed down from the soil and enter the water bodies. From the water bodies, they are taken up by aquatic plants and animals. In this way, these chemicals enter the food chain. As they cannot decompose, they accumulate progressively at each trophic level. This increase in the concentration of harmful chemicals with each step of the food chain is called biomagnification. As human beings occupy the top level in any food chain, these chemicals accumulate in their bodies.
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RELATED QUESTIONS
The following statement is true or false :
In biology, human beings are called producers.
Which organisms belong to third and fourth trophic levels in the food chain comprising the following?
Rats, Plants, Hawk, Snakes
Name two predators of snakes in a food web operating in a forest ecosystem.
Consider the following food chain
(i) Plants → Mice → Snakes → Hawks
(ii) Plants → Mice →Hawks
If energy available at the producer level in both the food chains is 100 J, in which case will hawks get more energy as food and by how much? Justify your answer.:
What provides the energy which then flows through a food chain?
(a) glucose
(b) oxygen
(c) respiration
(d) sunlight
The ten per cent law is associated with
(a) transfer of energy from various trophic levels to decomposers in a food chain
(b) transfer of ATP energy into muscular energy
(c) transfer of chemical energy from one organism to another
(d) transfer of sun's energy to the organisms called producers.
Food chains are very important for the survival of most species.
Matter and energy are two fundamental inputs of an ecosystem. Movement of:
______ obtained energy from the chemical breakdown of dead organisms.
Differentiate between herbivores and carnivores.
Assertion (A): The energy which passes to the herbivores does not come back to autotrophs.
Reason (R): The flow of energy in a food chain is unidirectional.
