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प्रश्न
Explain why, a food chain usually cannot have more than three or four steps.
Explain why food chains generally consist of three or four steps.
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उत्तर
At each trophic level in a food chain, a large portion of the energy available is utilised for the maintenance of organisms in that trophic level and is lost as heat. Food chains usually cannot have more than three or four steps because the energy available for organisms in any additional step will be so small that it will be insufficient to sustain the life of those organisms.
संबंधित प्रश्न
Give reason to justify the following: Flow of energy in a food chain is unidirectional.
In the following food chain, 20,000 J of energy was available to the plants. How much energy would be available to man in this chain?
Plants → Sheep → Man
Consider the food chain :
Grass → Deer → Lion
What will happen if all the lions are removed from the above food chain?
Write one or two word for the following statement/definition :
Each level of food chain where transfer of energy takes place
Which of the following are decomposers of dead organisms?
| Bacteria | Fungi | Viruses |
| (a) no | yes | yes |
| (b) yes | no | yes |
| (c) yes | yes | no |
| (d) yes | yes | yes |
In the figure given alongside, the various trophic levels are shown in the form of a pyramid. At which trophic level the maximum energy is available?
One of the following is not a consumer. This one is :
(a) giraffe
(b) antelope
(c) algae
(d) alligator
Which of the following is not a producer?
(a) grass
(b) zooplankton
(c) phytoplankton
(d) paddy
One of the following is a micro-consumer. This one is :
(a) ant
(b) lice
(c) fungi
(d) mosquito
The sea water contains water beetles, tadpole, fish and weeds.
Which organism is a secondary consumer?
The following is a food chain that ends with human :
plants → bee → human
How do bees provide food for humans?
Fill in the following blank with suitable word :
Plants → Antelope → ............
Explain how harmful chemicals enter our bodies.
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.:
In addition to wheat plants, a crop field ecosystem has organisms such as snake, peacock, eagle and mice. If the wheat plants are sprayed with pesticides periodically, which of the following will have the minimum concentration of pesticides in the body?
(a) snake
(b) eagle
(c) mice
(d) peacock
What are decomposers? What will be the consequence if the decomposers are completely eradicated from an ecosystem? Give justification in support of your answer.
In a given food chain if the amount of energy at the fourth trophic level is 6 kJ, what will be the energy available at the producer level?
Natural agents like ______ are the decomposition factors breaking complex forms into simpler units.
Study the picture given below showing three food chains (a), (b) and (c) and answer the following questions:
- Name the type of ecosystems that exist in food chains (b) and (c).
- The first trophic level in all food chains is producers. Why? What percentage of solar energy do these producers capture for their use?
- Why are the arrows shown in the diagram in one direction only and not vice versa? Justify.
