Multiple Choice Questions
1 .The % of solar radiation absorbed by all the green plants for the process of photosynthesis is about: [NCERT Exemplar]
(a) 1%
(b) 5%
(c) 8%
(d) 10%
Ans. (a) 1%
Explanation :
For the process of photosynthesis, green plants capture roughly 1% of the energy of sunlight that falls on their leaves. This energy isconverted into chemical energy, which is then used to make food.
2. Which of the following statements is incorrect ?
(a) All green plants and blue green algae are producers.
(b) Green plants get their food from organic compounds.
(c) Producers prepare their own food from inorganic compounds.
(d) Plants convert solar energy into chemical energy.
Ans. (b) Green plants get their food from organic compounds.
Explanation :Green plants and algae are both producers which means that they can make their own food with the help of inorganic substances and sun energy, through the process of photosynthesis.
3. At which trophic level is maximum energy available in the figure given below for the various tropic levels in a food chain ?
(a) T 4
(b) T 2
(c) T 1
(d) T3
Ans. (c) T1
Explanation : All ecosystems are characterised by a unidirectional flow of energy. At each trophic level, most of the energy available is utilised for respiration and excretion and only ten percent of the available energy is passed on to the next level because only ten percent of the available energy can be passed on to the next trophic level, higher trophic levels have substantially less energy content and the number of trophic levels in a food chain is limited. The lower the trophic level higher will be energy content. Hence, the greatest amount of energy is expected to be in trophic level T1.
4. What will happen if deer is missing in the food chain given below ? [NCERT Exemplar]
Grass → Deer → Tiger
(a) The population of tiger increases.
(b) Tiger will start eating grass.
(c) The population of grass decreases.
(d) The population of tiger decreases and the population of grass increases.
Ans. (d) The population of tiger decreases and the population of grass increases.
Explanation : The tiger is a secondary consumer which eats deer. If the deer is missing, there will be no food for the tiger. So if deer are missing, the population of grass will increase.
5. Flow of energy in an ecosystem is always: [NCERT Exemplar]
(a) unidirectional(b) bidirectional
(c) multidirectional
(d) no specific direction
Ans. (a) unidirectional
Explanation :The energy flow in an ecosystem is always unidirectional. Energy coming from the sun in most natural ecosystems, is used by producers, and then passed on to subsequent trophic levels in the form of food. Energy never flows in the reverse direction, it always get transferred from the prey to the predator.
6. Food chain does not comprise of which of the following groups of organisms?*
(i) Grass, lion, rabbit, wolf
(ii) Plankton, man, fish, grasshopper
(iii) Wolf, grass, snake, tiger
(iv) Frog, snake, eagle, grass, grasshopper
(a) (i), (iii)
(b) (iii), (iv)
(c) (ii), (iii)
(d) (i), (iv)
Ans. (c) (ii), (iii)
Explanation : The flow of energy from one organism to another taking part atvarious biotic levels forms a food chain. A food chain describes the feeding relationships between the organisms within that ecosystem. Food chain (ii) is an aquatic food chain so grasshopper cannot be a part of it. In food chain (iii), wolf, snake and tiger all are carnivores. There is no herbivore to eat grass or herbivore is missing from the chain.
7. In an ecosystem, the 10% of energy available for transfer from one trophic level to the next is in the form of :* [NCERT Exemplar]
(a) heat energy
(b) light energy
(c) mechanical energy
(d) chemical energy
Ans. (d) chemical energy
Explanation : The sun is the ultimate source of energy in an ecosystem, and green plants capture it and convert it to chemical energy, which is then stored in the form of carbohydrates. This chemical energy, in the form of food, is transmitted down the food chain in the ecosystem from one trophic level to the next following 10 per cent law according to which only 10% of the chemical energy is transferred from one trophic level to subsequent higher trophic level.
Other questions will be updated soon....
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