What role does competition play in an ecosystem, and what would happen without it?
Hint. The chapter states this as a direct cause-and-effect relationship.
✦ Organisms compete for common resources like food, water, physical space, or sunlight, and this competition 'helps control population size and keeps the ecosystem balanced.' Without competition, one species could multiply too much, since nothing would be checking its numbers, causing an imbalance in the ecosystem.
Define mutualism, commensalism and parasitism, with the chapter's own example of each.
Hint. One relationship benefits both organisms, one benefits only one while leaving the other unaffected, and one benefits only one while harming the other.
✦ Mutualism: both organisms benefit — the chapter's example is honeybees and flowers (the bee gets nectar, the flower gets pollinated). Commensalism: one organism benefits while the other is not affected — the chapter's example is orchids on trees (the orchid gets physical support, the tree branch is unaffected). Parasitism: one organism benefits while the other is harmed — since the chapter's example is ticks on the body of dogs — the tick feeds on the dog's blood, while the dog gets skin irritation.
In the tick-and-dog example, what exactly does each organism experience, and why does this make it parasitism rather than commensalism?
Hint. Commensalism requires the second organism to be genuinely unaffected — check whether that's true here.
✦ The tick feeds on the dog's blood and benefits directly from this food source, while the dog experiences skin irritation as a result. Because the dog is actively harmed (not simply unaffected, as the tree branch is in the orchid example), this relationship is classified as parasitism rather than commensalism — the defining difference between the two categories is exactly whether the second organism is harmed or left unaffected.
Be a scientist: what did A.J.T. Johnsingh's research at Bandipur National Park show about predators and prey?
Hint. His finding connects directly to why healthy prey populations matter for the predators above them.
✦ A.J.T. Johnsingh's research showed how predators like tigers and leopards rely on prey, such as deer and wild boar, while he was working in Bandipur National Park, Karnataka — proving that a healthy prey population is key to predator survival. This is the same underlying logic as the chapter's food pyramid, which is why predators cannot exist in stable numbers without a sufficiently large population of prey beneath them.
A student claims 'competition is always bad for an ecosystem, since it means organisms are fighting.' Correct this using the chapter's own framing.
Hint. The chapter frames competition as a control mechanism, not a destructive force.
✦ This is incorrect — competition is not framed as harmful in this chapter, but as a mechanism that helps control population size and keeps the ecosystem balanced. Rather than being purely destructive, competition prevents any single species from multiplying unchecked, which the chapter states directly would otherwise cause an imbalance in the ecosystem — so competition is better understood as a stabilising interaction, not simply conflict.
Solutions written by the tuition.in editorial team and checked against NCERT Curiosity — Textbook of Science for Grade 8, Chapter 12 (hecu112.pdf), Reprint 2026-27, pages 190-209. Questions are referenced from the NCERT textbook for identification.
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