Q. With reference to food chains in ecosystems, consider the following statements :
- A food chain illustrates the order in which a chain of organisms feed upon each other.
- Food chains are found within the populations of a species.
- A food chain illustrates the numbers of each organism which are eaten by others.
Which of the statements given above is/are correct? (UPSC Prelims 2013)
Answer:
1 only
Notes: The correct answer is
[A] 1 only. A food chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another. It represents the functional relationship between different biotic components of an ecosystem.
- Illustration of Feeding Order (Statement 1 is Correct): A food chain precisely shows the transfer of energy from producers (green plants) to various levels of consumers (herbivores, carnivores, and apex predators). For example: Grass → Grasshopper → Frog → Snake → Hawk. Each step in this chain represents a trophic level.
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- Found within Populations (Statement 2 is Incorrect): A food chain involves a sequence of different species, not a single population of one species. A population refers to a group of individuals of the same species living in the same area. In contrast, a food chain describes the interaction between different populations (e.g., the population of deer feeding on the population of grass).
- Illustration of Numbers (Statement 3 is Incorrect): A food chain shows the direction of energy flow and who eats whom, but it does not illustrate the numbers or the quantity of organisms at each level. The representation of the number of individuals at each trophic level is called a Pyramid of Numbers, which is a type of ecological pyramid, not a simple food chain.
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Key Differences to Remember:- Food Chain: A single, linear path of energy flow (Grass → Goat → Human).
- Food Web: A complex network of interconnected food chains representing all possible feeding relationships in an ecosystem.
- Ecological Pyramid: A graphical representation of the relationship between different organisms in an ecosystem in terms of numbers, biomass, or energy.