Important Ecology MCQs. Ecology plays a crucial role within the broader field of environment and ecology. It serves as a foundational concept for achieving success in competitive exams such as Civil Services, State exams, SSC, Railways, Banking, and more. Mastering these subjects offers a unique advantage, allowing you to gain invaluable insights into the country’s environmental legacy. With a focus on Environment, Biodiversity, and Ecology, this knowledge not only sharpens your competitive edge but also equips you to excel in these challenging exams.
MCQs on Ecology – Objective Questions and Answers
Q21. Concerning the food chains in ecosystems, which of the following kinds of an organism is/are known as decomposer organism/organisms? I.A.S. (Pre) 2013
Virus 2. Fungi3. Bacteria
Select the correct answer using the code given below:
[A] Only 1
[B] 2 and 3
[C] 1 and 3
[D] All of these
View Explanation
Correct Answer is B.
Decomposers act as nature’s recyclers by breaking down organic material found in the remains of plants and animals. “Organic matter” refers to substances derived from living organisms.
Decomposers, primarily microorganisms like bacteria and fungi (including yeasts and molds), decompose the bodies of dead organisms and release compounds that producers can utilize.
Q22. Which of the following are the primary consumers in an ecosystem? Select the correct answer from the codes given below: U.P.P.C.S. (Mains) 2006
Ants 2. Deer3. Fox 4. Tiger
Code :
[A] 1 and 2
[B] 2 and 3
[C] 1, 2 and 3
[D] 2, 3 and 4
View Explanation
Correct Answer is A.
In a food chain, herbivores are typically regarded as primary consumers. Among the options provided, deer is herbivorous, making it a primary consumer.
Ants can act as both decomposers and primary consumers since they eat plants and derive energy from cellulose. Tigers are carnivorous, while foxes are omnivorous. Importantly, primary consumers obtain their energy by feeding on primary producers (plants).
Q23.In a food chain, man is : U.P.P.C.S. (Pre) 2016
[A] producer
[B] only primary consumer
[C] only secondary consumer
[D] primary as well as a secondary consumer
View Explanation
Correct Answer is D.
In a food chain, there are various trophic levels: autotrophs, primary consumers, secondary consumers, and tertiary consumers. Primary consumers are herbivores that feed on plants, secondary consumers are small carnivores that feed on primary consumers, and tertiary consumers are larger carnivores.
Humans occupy the roles of both primary and secondary consumers, as they consume both plant-based products and meat.
Q24. 10 percent law is related with: Chhattisgarh P.C.S. (Pre) 2016
[A] Transfer of energy as food from one trophic level to other
[B] Transfer of heat from one matter to another
[C] Transfer of birds from one zone to another
[D] Transfer of water from one zone to another
[E] None of these
View Explanation
Correct Answer is A.
The Ten Percent Law of energy transfer between trophic levels was introduced by Raymond Lindeman in 1942. This law states that when energy is transferred from one trophic level to the next, only about ten percent of the energy from organic matter is stored as biomass (flesh).
The remaining energy is lost during transfer, through respiration, or due to incomplete digestion by organisms at higher trophic levels. When an organism is consumed, only 10% of the energy from its food is converted into flesh and made available to the next trophic level (carnivores or omnivores).
Therefore, at each level of the food chain, only 10% of the accumulated energy is converted into body mass.
Q25. In the marine environment, the main primary producers are: U.P.P.C.S. (Mains) 2005
[A] Phytoplanktons
[B] Seaweeds
[C] Marine angiosperms
[D] Aquatic bryophytes
View Explanation
Correct Answer is A.
Phytoplankton, also called microalgae, are similar to land plants because they contain chlorophyll and depend on sunlight for growth. Most phytoplankton are buoyant, floating near the ocean’s surface where sunlight can reach.
They also need inorganic nutrients like nitrates, phosphates, and sulfur, which they convert into proteins, fats, and carbohydrates.
Q26. Among the biotic components of the ecosystem, the producer system is: U.P.P.C.S. (Pre) 2013
[A] Cow
[B] Peacock
[C] Tiger
[D] Green Plants
View Explanation
Correct Answer is D.
Plants are self-sustaining organisms that produce complex organic compounds like carbohydrates, fats, and proteins, typically using light energy through photosynthesis. Known as autotrophs, they form the foundation of the food chain in all ecosystems and are referred to as primary producers.
Q27. Trophic level-I includes – M.P.P.C.S. (Pre) 2016
[A] Herbivorous animals
[B] Carnivorous animals
[C] Omnivorous animals
[D] Green plants
View Explanation
Correct Answer is D.
Each step or level in the food chain represents a trophic level. Trophic level I consists of autotrophs or producers (such as green plants) that capture solar energy and make it available to heterotrophs or consumers.
Herbivores, or primary consumers, occupy the second level, followed by small carnivores at the third, and large carnivores, or tertiary consumers, at the fourth trophic level.
Q28. What is true about ecosystem? U.P.P.C.S. (Pre) 2019
[A] Primary consumers are least dependent upon producer
[B] Primary consumers are out-number producers
[C] Producers are more than primary consumers
[D] Secondary consumers are the largest and most powerful
View Explanation
Correct Answer is C.
In most ecosystems, there are typically more producers than primary consumers, and more primary consumers than secondary consumers, with this pattern continuing up the food chain.
Q29. Which one of the following pairs is correctly matched? U.P.P.C.S. (Pre) 2015
[A] Mountain – Most stable ecosystem
[B] Abiotic Component – Bacteria
[C] Green plants – Ecosystem
[D] Rainfall – Global Warming
View Explanation
Correct Answer is C.
All the pairs mentioned in the question are related to ecosystems, but only option (c) is correctly matched. An ecosystem is a community of living organisms interacting with the non-living components of their environment. Since plants are living organisms, they are naturally part of an ecosystem.
Q30. The correct order in the food chain of the various components of a terrestrial grass ecosystem is – U.P.P.S.C. (GIC) 2010
[A] Grass, Grasshopper, Frog, Snake
[B] Grass, Grasshopper, Snake, Frog
[C] Grasshopper, Frog, Grass, Snake
[D] Grasshopper, Snake, Frog, Grass
View Explanation
Correct Answer is A.
Any substance consumed to provide nutritional support for an organism is called food. Plants are autotrophic and produce their own food, while animals rely on plants for nourishment. The food chain illustrates the flow of energy through various organisms in an ecosystem, and this flow is unidirectional. In the food chain described, the correct order of the components is:
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