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 populations 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?

Statement 1 is correct. A food chain is a linear sequence showing who eats whom, from producer to primary consumer to secondary and tertiary consumers. Energy and matter move along this sequence, which is why the order matters.

Statement 2 is wrong. A food chain links different species across trophic levels; it does not describe feeding within one population. Feeding relations inside a species belong to population studies, not to food chains.

Statement 3 is wrong. A food chain shows the order of feeding, not how many individuals of each species are eaten. Numbers across trophic levels are represented by pyramids of numbers, which can even be inverted, as in a tree ecosystem where one tree supports many insects. Biomass and energy pyramids are the other ways to show quantities.

Core concept: trophic structure of ecosystems, and the difference between food chains, food webs and ecological pyramids. In Mains, food webs explain why removing one species can cascade through an ecosystem, a point that often comes up in biodiversity and conservation answers.

Trap: Aspirants accept statement 3 because food chains are often drawn with numbers. The concept is about sequence, not quantity; quantities belong to pyramids.