168 practice questions on Ecology & Ecosystems from the Environment & Ecology section of the UPSC Prelims syllabus.
168 come with a written explanation and 34 are actual previous year questions.
Try the sample set below - the answer stays hidden until you ask for it.
51 Easy82 Medium35 Hard34 from past papers
Sample questions
Q1
Previous year questionmedium
Which of the following have species that can establish symbiotic relationship with other organisms?
1. Cnidarians
2. Fungi
3. Protozoa
Select the correct answer using the code given below.
A1 and 2 only
B2 and 3 only
C1 and 3 only
D1, 2 and 3
Show answer and explanation
Correct answer: D - 1, 2 and 3
Cnidarians such as corals host symbiotic zooxanthellae algae, so statement 1 holds. Fungi form symbioses such as lichens with algae and mycorrhizae with plant roots, so statement 2 holds. Protozoa also form symbiotic relationships, for example the cellulose-digesting protozoa living in the guts of termites and ruminants, so statement 3 holds. Since all three groups have symbiotic species, the answer is 1, 2 and 3.
Q2
Previous year questioneasy
Which one of the following is the best description of the term 'ecosystem'?
AA community of organisms interacting with one another
BThat part of the Earth which is inhabited by living organisms
CA community of organisms together with the environment in which they live
DThe flora and fauna of a geographical area
Show answer and explanation
Correct answer: C - A community of organisms together with the environment in which they live
An ecosystem is a community of organisms together with the non-living (abiotic) environment with which they interact and exchange energy and matter. A community of organisms alone (option a) ignores the physical environment; the part of Earth inhabited by life (option b) describes the biosphere; and the flora and fauna of an area (option d) is merely the biotic component, so all three are incomplete or wrong.
Q3
Previous year questionmedium
In case of which one of the following biogeochemical cycles, the weathering of rocks is the main source of release of nutrient to enter the cycle?
ACarbon cycle
BNitrogen cycle
CPhosphorus cycle
DSulphur cycle
Show answer and explanation
Correct answer: C - Phosphorus cycle
The phosphorus cycle is a sedimentary cycle lacking a significant gaseous phase, and phosphorus enters the cycle mainly through the weathering of phosphate-bearing rocks, so this is correct. The carbon cycle is driven by atmospheric carbon dioxide and photosynthesis, not rock weathering. The nitrogen cycle relies largely on atmospheric nitrogen fixed by microbes. The sulphur cycle has both atmospheric and sedimentary components but is not primarily rock-weathering driven. Hence the phosphorus cycle is the answer.
Q4
Previous year questionmedium
In the grasslands, trees do not replace the grasses as a part of an ecological succession because of
Ainsects and fungi
Blimited sunlight and paucity of nutrients
Cwater limits and fire
DNone of the above
Show answer and explanation
Correct answer: C - water limits and fire
In grasslands the establishment of trees is checked mainly by limited soil moisture (low and seasonal rainfall) and by recurrent fires that kill tree seedlings while the deep-rooted grasses regenerate, so option (c) is correct. Option (a) is wrong because insects and fungi are not the primary controls on tree invasion. Option (b) is wrong because grasslands generally have ample sunlight and reasonable nutrients. Since (c) is valid, option (d) is also wrong.
Q5
Previous year questionmedium
With reference to the planet Earth, consider the following statements :
I. Rain forests produce more oxygen than that produced by oceans.
II. Marine phytoplankton and photosynthetic bacteria produce about 50% of world's oxygen.
III. Well-oxygenated surface water contains several folds higher oxygen than that in atmospheric air.
Which of the statements given above is/are correct?
AI and II
BII only
CI and III
DNone of the above statements is correct
Show answer and explanation
Correct answer: B - II only
Oceans, through phytoplankton and photosynthetic bacteria, generate roughly half of the world's oxygen, more than rainforests, so statement I is wrong while statement II is correct. Statement III is also wrong because the oxygen dissolved in even well-aerated surface water is far less than the oxygen content of atmospheric air. Hence only statement II is correct.
Q6
Previous year questionmedium
What would happen if phytoplankton of an ocean is completely destroyed for some reason?
1. The ocean as a carbon sink would be adversely affected.
2. The food chains in the ocean would be adversely affected.
3. The density of ocean water would drastically decrease.
Select the correct answer using the codes given below:
A1 and 2 only
B2 only
C3 only
D1, 2 and 3
Show answer and explanation
Correct answer: A - 1 and 2 only
Phytoplankton fix carbon dioxide through photosynthesis, so their loss would weaken the ocean as a carbon sink (statement 1), and as the base of marine food chains their destruction would disrupt those chains (statement 2). The density of ocean water depends on salinity and temperature, not on phytoplankton, so it would not drastically fall (statement 3 wrong). The answer is 1 and 2 only.
Q7
Previous year questioneasy
Which of the following leaf modifications occurs/occur in desert areas to inhibit water loss?
1. Hard and waxy leaves
2. Tiny leaves or no leaves
3. Thorns instead of leaves
Select the correct answer using the codes given below.
A1 and 2 only
B2 only
C1 and 3 only
D1, 2 and 3
Show answer and explanation
Correct answer: D - 1, 2 and 3
Desert (xerophytic) plants adopt several leaf modifications to reduce transpiration. Hard, thick and waxy leaves cut down water loss through a tough cuticle. Tiny leaves or the absence of leaves reduce the surface area exposed for evaporation. Converting leaves into thorns (as in cacti) drastically minimizes transpiring surface while photosynthesis shifts to the green stem. All three are genuine water-conserving adaptations, so the answer is 1, 2 and 3.
Q8
Previous year questioneasy
The term "sixth mass extinction/sixth extinction" is often mentioned in the news in the context of the discussion of
AWidespread monoculture practices in agriculture and large-scale commercial farming with indiscriminate use of chemicals in many parts of the world that may result in the loss of good native ecosystems.
BFears of a possible collision of a meteorite with the Earth in the near future in the manner it happened 65 million years ago that caused the mass extinction of many species including those of dinosaurs.
CLarge scale cultivation of genetically modified crops in many parts of the world and promoting their cultivation in other parts of the world which may cause the disappearance of good native crop plants and the loss of food biodiversity.
DMankind's over-exploitation/misuse of natural resources, fragmentation/loss of natural habitats, destruction of ecosystems, pollution and global climate change.
Show answer and explanation
Correct answer: D - Mankind's over-exploitation/misuse of natural resources, fragmentation/loss of natural habitats, destruction of ecosystems, pollution and global climate change.
The sixth mass extinction refers to the ongoing, human-driven loss of biodiversity caused by over-exploitation of resources, habitat destruction and fragmentation, pollution and climate change, which is captured by option (d). Option (a) describes only one agricultural pressure and is too narrow to define the concept. Option (b) is wrong because the sixth extinction concerns present human impact, not a hypothetical future meteorite strike, even though the previous fifth extinction is linked to such an impact. Option (c) about GM crops describes a specific concern over crop biodiversity rather than the broad species extinction crisis. Hence option (d) is correct.
Practice all 168 Ecology & Ecosystems questions free
Timed practice, instant scoring, and explanations for every question. Free forever - no card, no catch.