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Assertion : In a food chain members of successive higher levels are fewer in number.

Reason : Number of organisms at any trophic level depends upon the availability of organisms which serve as food at the lower level.

  • If both Assertion and Reason are true and the reason is the correct explanation of the assertion

  • If both Assertion and Reason are true but the reason is not the correct explanation of the assertion

  • If Assertion is true statement but Reason is false

  • If both Assertion and Reason are false statements


If both Assertion and Reason are true and the reason is the correct explanation of the assertion

In a food chain the number of animals and biomass at the lower trophic level is abundant. Successive links of carnivores decrease rapidly in number until there are very few carnivores at the top.


Enzyme and carbohydrates dominate in the digestive tract of

  • carnivores

  • omnivores

  • parasites

  • herbivores



herbivore is an animal that gets its energy from eating plants and only plants. These animals eat more carbohydrate food, therefore enzyme carbohydrate dominates.


When a natural predator (living being) is applied on the other pathogen organism to control them, this process is called

  • biological control

  • genetic engineering

  • artificial control

  • confusion technique


biological control

Biological control methods include using natural predators of pests, using resistant varieties, crop rotation etc.


The food chain starts from :

  • consumer

  • producer

  • decomposer

  • nitrogen fixation



Food chain initiates from producers. Transfer of food energy from producers takes place through a series of organisms, i.e herbivores to carnivores to decomposers with repeated eating and being eaten is known as food chain.

Producers utilise the radient energy of sun which is transformed to chemical energy during photosynthesis. Thus, green plants occupy first trophic level in any food chain.


July 11 is observed as:

  • World population day

  • No tobacco day

  • World environment day

  • World health day


World population day

World Population Day is celebrated on 11th July.

No Tobacco Day is celebrated on 31st May.

World Environment Day is celebrated on 5th June.

World Health Day is celebrated on 7th April.


Biological Oxygen Demand (BOD) is a measure of

  • industrial wastes poured into water bodies

  • extent to which water is polluted with organic compounds

  • amount of carbon monoxide inseparably combined with haemoglobin

  • amount of oxygen needed by green plants during night


extent to which water is polluted with organic compounds

To measure water pollution, BOD or Biological Oxygen Demand test is done. In this test, amount of oxygen sufficient to degrade waste organic matter by bacteria in a sample is measured. The more oxygen used up by the bacteria to degrade the organic matter in the sample, the greter the BOD would be.


The 10% energy transfer law of food chain was given by

  • Stanley

  • Weismann

  • Lindemann

  • Tansley



Only about 10% of the energy is transferred from one trophic level to the next. This 10% law of energy transfer was proposed by Lindemann (1942).


Some students, during a study, caught, marked and released 80 fishes in a pond. Later 100 fishes were caught at random. Among these 40 were found to be marked. What is the approximate number of fishes in the pond?

  • 50

  • 100

  • 200

  • 4000



According to Petersons Mark and Recapture Method, the population (P) is given by

P = m(r + u)/r

where m = number of marked fishes

          r = number of marked fishes recaptured

          u = number of unmarked fishes captured

Here, m = 80; r = 40; u = 100 - 40 = 60

Therefore, P = m (r + u)r

P = 80 (40 + 60)40

P = 200


As insecticides reach at higher trophic level in food chain their concentration :

  • increases

  • become irregular

  • remain constant

  • decreases



Toxic pesticides such as BHC and DDT etc., are not easily degraded and are long lasting in the environment. They show biological magnification or food chain concentration i.e. the continuous increase in concentration of a toxicant at successive trophic levels in a food chain.


The term 'ecosystem' was coined by :

  • E.P. Odum

  • A.G. Tansley

  • Carl Mobious

  • W. Clementus


A.G. Tansley

The term 'ecosystem' was coined by A.G. Tansley in 1935 and defined it as "the system resulting from the integration of all the living and non living factors of environment".