Population and Community (12.2) — "How Nature Works in Harmony"

1. 12 marks

   Define a population, in the chapter's own words, using Activity 12.2's quadrat-counting method.

   Hint. The chapter's definition follows directly from counting how many of ONE kind of organism live in ONE place at ONE time.

   ✦ 'The population is a group of the same type of organisms in a habitat at a given time' — established by Activity 12.2, where students mark a 1 m × 1 m area, identify organisms in it, and count how many individuals of each kind are present, since that count is exactly what defines a population.

2. 23 marks

   In Activity 12.2's quadrat, a group counted 20 of one plant and 5 of another in the same 1 m × 1 m area. What would happen to a habitat if it contained only ONE type of living organism?

   Hint. The chapter poses this exact scenario directly — think about what happens when every individual needs the exact same things.

   ✦ If all organisms in a habitat were the same type, they would all have identical requirements — the same food, water and space — leading directly to competition and possible scarcity of resources, since nothing in the habitat would be using resources differently or filling a different role. This is exactly why real habitats support many different populations rather than just one.

3. 33 marks

   Define a community, and explain how it differs from a population.

   Hint. A population is one kind of organism; a community is what you get when you add every other kind sharing the same space.

   ✦ 'A community comprises different populations sharing the same habitat. The biotic components of a habitat, such as the plants, animals, and microorganisms together form the community.' A population is restricted to ONE type of organism in a habitat, while a community is ALL the different populations of plants, animals and microorganisms present together, because they interact with and depend on one another for survival.

4. 43 marks

   Name the parts of a flower involved in pollination, and explain why pollination matters beyond just producing colourful flowers.

   Hint. The 'Ever heard of' box names four flower parts and states exactly what pollination is essential for.

   ✦ A flower has a stalk, sepals (green leafy structures), petals, and two reproductive parts — carpels (female) and stamens (male). Stamens release pollen grains, which wind, water, insects, bats and birds carry to the carpels of the same or different flowers — this is pollination. It matters because it 'is essential for the formation of fruits and seeds,' meaning it is a biotic interaction directly responsible for how plant populations reproduce.

5. 52 marks

   Which agents can carry pollen from stamens to carpels, according to the chapter?

   Hint. Both non-living forces and living organisms are named as pollen carriers.

   ✦ Wind, water, insects, bats, and birds — a mix of abiotic agents (wind, water) and biotic agents (insects, bats, birds) all capable of carrying pollen between flowers.

6. 63 marks

   Explain how Activity 12.2's quadrat method could be repeated a year later to check whether a population is growing, shrinking, or stable.

   Hint. The method itself is just counting at a given place and time — what would change between two separate counts to make a comparison meaningful?

   ✦ Since a population count only captures the number of one type of organism at a specific place and time, repeating the exact same 1 m × 1 m quadrat count at the same location a year later would give a second, comparable snapshot — comparing the two counts would show whether the population had grown, shrunk, or stayed roughly stable, since any change in the counted number directly reflects a change in that population's size over the intervening year.

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.