Environment chapter practice
Practise 80+ Ecosystems and Ecological Relationships MCQs for UPSC Prelims in Environment, including 8+ previous year questions. The sample set below is shown with correct answers and explanations.
12 sample questions are shown here; sign up free to practise all 80.
Consider the following: 1. Carabid beetles 2. Centipedes 3. Flies 4. Termites 5. Wasps Parasitoid species are found in how many of the above kinds of organisms?
Explanation
Correct. Parasitoid species are found among wasps (e.g., ichneumonid wasps), flies (e.g., tachinid flies), and carabid beetles (some Lebiini species). Centipedes and termites are not parasitoids.
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?
Explanation
Correct. Phosphorus has no significant gaseous phase. The primary natural input to the phosphorus cycle is the weathering of phosphate-bearing rocks such as apatite.
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?
Explanation
Correct. Cyanobacteria are photosynthetic prokaryotes and diatoms are photosynthetic microalgae; both fix carbon and are primary producers in oceanic food chains.
Which one of the following is the correct sequence of a food chain?
Explanation
Correct. Diatoms are microscopic algae (primary producers) eaten by crustaceans (primary consumers), which are in turn eaten by herrings (secondary consumers). This is a classic marine grazing food chain.
Lichens, which are capable of initiating ecological succession even on a bare rock, are actually a symbiotic association of:
Explanation
Correct. Lichens are a mutualistic symbiosis between a fungal partner (mycobiont) and a photosynthetic partner (photobiont), which is typically a green alga or sometimes a cyanobacterium.
With reference to the food chains in ecosystems, which of the following kinds of organism is/are known as decomposer organism/organisms? 1. Virus 2. Fungi 3. Bacteria Select the correct answer using the codes given below.
Explanation
Correct. Fungi and bacteria are the principal decomposers in ecosystems. They secrete enzymes that break down dead organic matter and recycle nutrients back into the soil.
With reference to food chains in ecosystems, consider the following statements: 1. A food chain illustrates the order in which a chain of organisms feed upon each other. 2. Food chains are found within the population of a species. 3. A food chain illustrates the numbers of each organism which are eaten by others. Which of the statements given above is/are correct?
Explanation
Correct. A food chain shows the sequential feeding relationships among different species. Statement 2 is wrong because food chains span multiple species, not a single population. Statement 3 is wrong because food chains show who eats whom, not quantities.
In the grasslands, trees do not replace the grasses as a part of an ecological succession because of:
Explanation
Correct. Grasslands persist as a climax community because insufficient rainfall limits tree growth and periodic fires destroy tree seedlings while grass root systems survive and regenerate quickly.
Consider the following statements about primary succession: 1. It begins on a substrate that has never been colonised before. 2. It proceeds faster than secondary succession because there is no competition. 3. Pioneer species in primary succession on bare rock are typically lichens. Which of the statements given above is/are correct?
Explanation
Correct. Primary succession occurs on barren substrates like lava flows or bare rock (Statement 1), and lichens are classic pioneer species that initiate soil formation on rock surfaces (Statement 3). It is slower, not faster, than secondary succession.
In ecology, the term 'protocooperation' refers to:
Explanation
Correct. Protocooperation is a type of facultative mutualism where both interacting species benefit, but neither depends on the other for survival. An example is the oxpecker-zebra relationship.
Which of the following is NOT a characteristic of a climax community?
Explanation
Correct. In a climax community, net primary productivity approximately equals community respiration, so net ecosystem productivity is near zero. High NPP relative to respiration is characteristic of early successional stages, not the climax.
Consider the following pairs: Organism - Type of consumer 1. Grasshopper - Primary consumer 2. Frog - Secondary consumer 3. Snake - Tertiary consumer 4. Hawk - Quaternary consumer Which of the above pairs is/are correctly matched?
Explanation
Correct. In a typical food chain: grasshopper eats grass (primary consumer), frog eats grasshopper (secondary consumer), snake eats frog (tertiary consumer), and hawk eats snake (quaternary consumer).
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