In-text Questions — Why Reproduce — How do Organisms Reproduce?

1. 12 marksNCERT Cl-10 Science, In-text Qs after §7.1.1, Q1

   What is the importance of DNA copying in reproduction?

   Hint. Reproduction is really just cell division plus something extra — think about what that extra thing has to preserve.

   Step 1 — Recall what a new cell needs. A new cell needs its own organised cellular apparatus to maintain life processes, not just a copy pushed out with nothing to run it.

   Step 2 — State the role of DNA copying. DNA copying ensures that each new cell created during reproduction carries the instructions needed to build and run its own cellular apparatus, which is why DNA copying is always accompanied by creation of additional cellular apparatus before the cell divides.

   Step 3 — Note the deeper consequence. Since no biochemical reaction is perfectly reliable, DNA copying also introduces small variations each time, which is the basis for the variation that drives evolution.

   ✦ Answer: DNA copying is what allows a new cell to inherit the instructions for its own cellular apparatus, and its natural (if slight) inaccuracy is also the source of variation between generations — the basis for evolution.

   Where students slip. Describing DNA copying as if it must be perfect for reproduction to work — the chapter specifically notes it's not perfectly accurate, and that imperfection is essential, not a flaw to be ignored.

2. 22 marksNCERT Cl-10 Science, In-text Qs after §7.1.1, Q2

   Why is variation beneficial to the species but not necessarily for the individual?

   Hint. Think about what happens to a single variant individual versus what happens to the whole population when the environment suddenly changes.

   Step 1 — Consider the individual. A particular variation in a single individual might be neutral, harmful, or simply unnecessary for that individual's own survival in the current environment.

   Step 2 — Consider the population. Across a whole population, though, having many different variations means that if the environment changes drastically (e.g. a sudden temperature rise), at least some individuals with a suitable variation are likely to survive and continue the species.

   Step 3 — State the conclusion. So variation doesn't need to help every individual — it only needs to ensure that enough variants exist somewhere in the population to survive an unpredictable future change.

   ✦ Answer: A given variation might do nothing for the individual carrying it, but across a whole population, having many different variations increases the chance that some individuals survive if the environment changes drastically — which is what keeps the species going, even though most individual variations never get 'used.'

   Where students slip. Assuming a beneficial variation must help every individual that has it — the benefit is at the population level, over unpredictable future changes, not a guaranteed advantage for any one organism right now.

Solutions written by the tuition.in editorial team and checked against the NCERT Class 10 Science textbook, Reprint 2026-27 (jesc107.pdf) — three in-text question sets (12 questions total) plus one end-of-chapter Exercise (11 questions, not 17 as some older manifests claim). Unchanged by rationalisation.. Questions are referenced from the NCERT textbook for identification.