1
The ozone layer, which absorbs harmful ultraviolet rays, lies mainly in the:
Correct answer: C. Stratosphere
Most ozone is found 15–35 km above the Earth, in the stratosphere.
easy
Environment and Ecology MCQs
Solved MCQs on ecosystems and food chains, the ozone layer, climate agreements, pollution and its diseases, biodiversity hotspots and environmental terms, for SSC and state exams.
20 MCQsUpdated 27 October 2026
This set covers the ozone layer, climate agreements such as the Paris Agreement, food chains and trophic levels, eutrophication, biodiversity hotspots and other key ideas of environmental science.
Environment questions often combine science with international agreements. Note what each agreement aims to achieve, since options frequently swap them.
- 2
The ozone layer is damaged mainly by:
Correct answer: C. Chlorofluorocarbons (CFCs)
CFCs, once used in fridges and aerosol sprays, release chlorine that breaks down ozone.
easy - 3
The international treaty to phase out ozone-depleting substances is the:
Correct answer: B. Montreal Protocol
The Montreal Protocol (1987) is widely seen as the most successful environmental treaty.
medium - 4
The Kyoto Protocol (1997) is concerned with:
Correct answer: A. reducing greenhouse gas emissions
It set binding targets for developed countries to cut greenhouse gas emissions.
medium - 5
The Paris Agreement of 2015 aims to limit global warming to:
Correct answer: A. well below 2 °C above pre-industrial levels
Countries agreed to keep warming well below 2 °C and to try to limit it to 1.5 °C.
medium - 6
The "Earth Summit" of 1992 was held at:
Correct answer: B. Rio de Janeiro
The UN Conference on Environment and Development at Rio led to the conventions on climate change and biodiversity.
medium - 7
The greenhouse gas released in the largest amount by human activities is:
Correct answer: D. Carbon dioxide
Burning coal, oil and gas releases carbon dioxide, the main driver of global warming.
easy - 8
Acid rain is caused mainly by:
Correct answer: C. Sulphur dioxide and nitrogen oxides
These gases dissolve in rain to form sulphuric and nitric acids, which damage buildings such as the Taj Mahal.
easy - 9
In a food chain, green plants are called:
Correct answer: D. Producers
Plants make their own food by photosynthesis; herbivores that eat them are primary consumers.
easy - 10
Organisms that break down dead plants and animals and return nutrients to the soil are called:
Correct answer: B. Decomposers
Bacteria and fungi are the main decomposers.
easy - 11
According to the 10% law, roughly how much energy passes from one level of a food chain to the next?
Correct answer: B. 10%
About 90% of the energy is used or lost as heat at each level, so food chains rarely have more than four or five links.
medium - 12
The increase in concentration of a toxic substance such as DDT at each higher level of a food chain is called:
Correct answer: B. Biomagnification
Top predators such as eagles collect the highest doses, which once caused their eggshells to thin.
medium - 13
Eutrophication of a lake is caused by:
Correct answer: B. excess nutrients such as nitrates and phosphates
Fertiliser and sewage nutrients cause algal blooms that use up oxygen and kill fish.
medium - 14
A high Biochemical Oxygen Demand (BOD) in a river indicates:
Correct answer: A. a high level of organic pollution
Microbes breaking down a lot of organic waste use up oxygen, so polluted water has a high BOD.
medium - 15
Minamata disease is caused by poisoning from:
Correct answer: D. Mercury
It was first found in Minamata, Japan, where factory waste put mercury into fish. Cadmium causes itai-itai disease.
medium - 16
"Blue baby syndrome" in infants is linked to drinking water with too much:
Correct answer: C. Nitrate
Nitrates reduce the blood's ability to carry oxygen, giving the skin a bluish colour. Excess fluoride causes fluorosis.
hard - 17
How many of the world's biodiversity hotspots lie wholly or partly in India?
Correct answer: C. 4
They are the Himalaya, Indo-Burma, the Western Ghats and Sri Lanka, and Sundaland (which includes the Nicobar Islands).
hard - 18
PM2.5, often reported in air-quality news, refers to particles with a diameter of:
Correct answer: D. 2.5 micrometres or less
These fine particles can go deep into the lungs and even the bloodstream.
medium - 19
A species found naturally in only one particular region of the world is called:
Correct answer: C. Endemic
The lion-tailed macaque of the Western Ghats is an example; exotic species come from elsewhere.
easy - 20
The Red List of threatened species is published by the:
Correct answer: A. IUCN
The International Union for Conservation of Nature classifies species as vulnerable, endangered, critically endangered and so on.
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