The depletion in atmospheric ozone layer in last century was due to :
- A.chlorofluorocarbon
- B.carbon monoxide
- C.methane
- D.pesticides
Correct answer
Explanation
The correct answer is A, chlorofluorocarbon. Chlorofluorocarbons (CFCs) used in refrigerators, air conditioners, aerosol sprays and foams were the main cause of ozone depletion in the twentieth century.
CFCs are very stable, so they drift up to the stratosphere, where ultraviolet rays break them and release chlorine atoms. A single chlorine atom can destroy thousands of ozone molecules in a chain reaction. The ozone hole over Antarctica was reported in 1985. The Vienna Convention (1985) and the Montreal Protocol (1987) led to a worldwide phase-out of CFCs, halons and other ozone-depleting substances, and the Kigali Amendment of 2016 added HFCs. 16 September is observed as World Ozone Day.
B is wrong: carbon monoxide is a poisonous air pollutant but does not destroy stratospheric ozone.
C is wrong: methane is a greenhouse gas, not the cause of ozone depletion.
D is wrong: pesticides harm soil and water life but did not cause ozone depletion.
Exam tip: Ozone killers — CFCs and halons; Montreal Protocol 1987; World Ozone Day 16 September.
Practice Questions
View allConsider the following :
1. Battery storage
2. Biomass generators
3. Fuel cells
4. Rooftop solar photovoltaic units
How many of the above are considered "Distributed Energy Resources"?
- A.Only one
- B.Only two
- C.Only three
- D.All four
Show answer
Battery storage, biomass generators, fuel cells and rooftop solar units are all small, local sources that generate or store power close to where it is used, which is what Distributed Energy Resources are.
Read the full explanation →Due to some reasons, if there is a huge fall in the population of species of butterflies, what could be its likely consequence/consequences ?
1. Pollination of some plants could be adversely affected.
2. There could be a drastic increase in the fungal infections of some cultivated plants.
3. It could lead to a fall in the population of some species of wasps, spiders and birds.
Select the correct answer using the code given below :
- A.1 only
- B.2 and 3 only
- C.1 and 3 only
- D.1, 2 and 3
Show answer
Butterflies are pollinators and also food for many animals, so their decline would hurt pollination and their predators; it has no direct link with fungal diseases of crops.
Read the full explanation →Consider the following statements :
1. Lions do not have a particular breeding season.
2. Unlike most other big cats, cheetahs do not roar.
3. Unlike male lions, male leopards do not proclaim their territory by scent marking.
Which of the statements given above are correct ?
- A.1 and 2 only
- B.2 and 3 only
- C.1 and 3 only
- D.1, 2 and 3
Show answer
Lions breed at any time of year and cheetahs cannot roar, but male leopards do mark their territory with scent.
Read the full explanation →Which one of the following National Parks lies completely in the temperate alpine zone?
- A.Manas National Park
- B.Namdapha National Park
- C.Neora Valley National Park
- D.Valley of Flowers National Park
Show answer
Set high in the Garhwal Himalaya of Uttarakhand, roughly between 3,200 and 6,600 metres, it lies wholly in the temperate alpine zone.
Read the full explanation →Consider the following kinds of organisms:
1. Copepods
2. Cyanobacteria
3. Diatoms
4. Foraminifera
Which of the above are primary producers in the food chains of oceans?
- A.1 and 2
- B.2 and 3
- C.3 and 4
- D.1 and 4
Show answer
Cyanobacteria and diatoms carry out photosynthesis, so they are phytoplankton, the primary producers at the base of ocean food chains.
Read the full explanation →