Choose the incorrect statements about energy flow from the following:
A. Except for the deep sea hydro-thermal ecosystem, sun is the only source of energy for all ecosystems on Earth.
B. Ecosystems need a constant supply of energy to synthesise the molecules they require, to counteract the universal tendency toward decreasing disorderliness.
C. All organisms are dependent for their food on decomposers, either directly or indirectly.
D. The energy trapped by a producer is either passed on to a consumer or the organism dies.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → B and C only
Energy enters an ecosystem from the sun (except in the deep sea hydro-thermal ecosystem) and is fixed by producers. From them it flows one way, to the consumers. Ecosystems also obey the second law of thermodynamics: without a steady supply of energy, order breaks down.
A. Except for the deep sea hydro-thermal ecosystem, sun is the only source of energy for all ecosystems on Earth. — True. This is the NCERT line; the hydro-thermal ecosystem is the one exception.
B. Ecosystems need a constant supply of energy to synthesise the molecules they require, to counteract the universal tendency toward decreasing disorderliness. — False. The universal tendency is toward increasing disorderliness. Energy is needed to fight this rise in disorder and build ordered molecules.
C. All organisms are dependent for their food on decomposers, either directly or indirectly. — False. All organisms depend for their food on producers, directly or indirectly. Decomposers themselves feed on dead matter that came from producers and consumers.
D. The energy trapped by a producer is either passed on to a consumer or the organism dies. — True. No energy stays in an organism for ever. When the producer dies, its energy passes into the detritus food chain.
The incorrect statements are B and C.
NCERT Extract:
Energy Flow – “Except for the deep sea hydro-thermal ecosystem, sun is the only source of energy for all ecosystems on Earth. … All organisms are dependent for their food on producers, either directly or indirectly. So you find unidirectional flow of energy from the sun to producers and then to consumers. … They need a constant supply of energy to synthesise the molecules they require, to counteract the universal tendency toward increasing disorderliness.”
Energy Flow – “… No energy that is trapped into an organism remains in it for ever. The energy trapped by the producer, hence, is either passed on to a consumer or the organism dies. Death of organism is the beginning of the detritus food chain/web.”