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Food chains are very important for the survival of most species. When only one element is removed from the food chain it can result in extinction of a species in some cases. The foundation of the food chain consists of primary producers.
Primary producers, or autotrophs, can use either solar energy or chemical energy to create complex organic compounds, whereas species at higher trophic levels cannot and so must consume producers or other life that itself consumes producers. Because the sun's light is necessary for photosynthesis, most life could not exist if the sun disappeared. Even so, it has recently been discovered that there are some forms of life, chemotrophs, that appear to gain all their metabolic energy from chemosynthesis driven by hydrothermal vents, thus showing that some life may not require solar energy to thrive.
10.1 If 10,000 J solar energy falls on green plants in a terrestrial ecosystem, what percentage of solar energy will be converted into food energy?
a) 10,000 J
b) 100 J
c) 1000 J
d) It will depend on the type of the terrestrial plant.
Answer
10.1 b) 100J
Only 1% of the energy of sunlight that falls on leaves is convert into food energy by plants
If 10,000J is the energy of sunlight;
(1/100) x 10000 = 100J
10.2 Mr. X is eating curd/yogurt. For this food intake in a food chain he should be considered as occupying
a) First trophic level
b) Second trophic level
c) Third trophic level
d) Fourth trophic level
Answer
10.2 c) Third Trophic leve l
Curd is made from milk which is obtained from cow
Cow is a primary consumer that feeds on producer (grass) and occupies the second trophic level
Consuming the produce obtained from an organism at second trophic level makes him belong to the third trophic level
10.3 The decomposers are not included in the food chain. The correct reason for the same is because decomposers:
a) Act at every trophic level of the food chain
b) Do not breakdown organic compounds
c) Convert organic material to inorganic forms
d) Release enzymes outside their body to convert organic material to inorganic forms
Answer
10.3 a) Act at every trophic level of the food chain
Thus they do not belong to any particular trophic level
10.4 Matter and energy are two fundamental inputs of an ecosystem. Movement of
a) Energy is bidirectional and matter is repeatedly circulating.
b) Energy is repeatedly circulation and matter is unidirectional.
c) Energy is unidirectional and matter is repeatedly circulating.
d) Energy is multidirectional and matter is bidirectional.
Answer
10.4 c) Energy is unidirectional and matter is repeatedly circulating
10.5 Which of the following limits the number of trophic levels in a food chain?
a) Decrease in energy at higher trophic levels
b) Less availability of food
c) Polluted air
d) Water
Answer
10.5 a) Decrease in energy at higher trophic level
The energy keeps on decreasing in each trophic level
This decrease is due to the heat released
As a result, the number of trophic levels is limited
