Energy and nutrients flow from one trophic level to another in an ecosystem. Which one of the following statements correctly describes the direction of flow of energy and nutrients in an ecosystem ?
- A.Energy flow is cyclic and nutrient flow is unidirectional.
- B.Energy flow is unidirectional and nutrient flow is cyclic.
- C.Both energy and nutrient flow are unidirectional.
- D.Both energy and nutrient flow are cyclic.
Correct answer
Explanation
The correct answer is B, Energy flow is unidirectional and nutrient flow is cyclic. Energy passes one way from the Sun through the food chain and is lost as heat, while nutrients are used again and again.
Green plants capture sunlight and store it as chemical energy in food. At each step from producer to herbivore to carnivore most of this energy is used for life processes and lost as heat, roughly ninety per cent at every level, so it can never flow back to the plants. Nutrients such as carbon, nitrogen and phosphorus behave differently: when plants and animals die, decomposers break down their bodies and return these elements to the soil, water and air, from where plants take them up again. These loops are called biogeochemical cycles.
Option A is wrong because it reverses the two: energy is not recycled and nutrients are not lost. Option C is wrong because nutrients are returned by decomposers. Option D is wrong because energy, once lost as heat, cannot be reused by producers.
Exam tip: Energy flows, matter cycles; ten per cent law of energy transfer.
Practice Questions
View allFor acid rain, the pH of rain water should be less than
- A.7.0
- B.6.6
- C.5.6
- D.8.0
Show answer
Rain is called acid rain when its pH falls below 5.6. Even clean rain is slightly acidic, because carbon dioxide in the air dissolves in it and forms weak carbonic acid, which brings its pH down to about 5.6.
Read the full explanation →Which one of the following statements with regard to ozone is not correct?
- A.Ozone is found mostly at 15-55 km in the atmosphere.
- B.Ozone is produced by gaseous chemical reactions.
- C.16th November is celebrated as the International Day for the Preservation of the Ozone Layer.
- D.Ozone is a form of oxygen in which three oxygen atoms are bounded together.
Show answer
The International Day for the Preservation of the Ozone Layer is observed on 16 September, not 16 November. The date marks the signing of the Montreal Protocol on 16 September 1987, the treaty that phased out chlorofluorocarbons and other ozone-depleting substances.
Read the full explanation →UNESCO World Heritage site Nanda Devi National Park is located in which one of the following States ?
- A.Arunachal Pradesh
- B.Uttarakhand
- C.Himachal Pradesh
- D.Sikkim
Show answer
Nanda Devi National Park lies in the Chamoli district of Uttarakhand, around India's second-highest peak, Nanda Devi. The park is a vast glacial basin ringed by high peaks and was inscribed on the UNESCO World Heritage list in 1988 for its wild, untouched landscape.
Read the full explanation →Which one of the following is related to global dimming?
- A.Fall of atmospheric pressure due to increased particulates
- B.Rise of atmospheric pressure due to increased particulates
- C.Rise of temperature due to increased particulates
- D.Fall of temperature due to increased particulates
Show answer
Global dimming is the drop in sunlight reaching the ground, and the cooling that follows, caused by particles in the air.
Read the full explanation →The financial instruments that generate proceeds for investment in environmentally sustainable and climate-suitable projects are called as :
- A.Green Bonds
- B.Carbon Bonds
- C.Climate Credit Bonds
- D.Social Impact Bonds
Show answer
A green bond is a debt instrument whose money can be spent only on projects that help the environment or the climate.
Read the full explanation →