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NCERT Class 10 Science Heredity: In-text questions (page 129) Solutions
AI-written, checked on 23 Oct 2026
Solutions written by Shishya, checked — not the board's official answers
Step-by-step working for every question of In-text questions (page 129) in NCERT's Class 10 Science book, chapter “Heredity”, written by Shishya. Each question is in our own short words; open the NCERT chapter for the exact wording and figures.
How these were checked: the solutions were drafted with AI and then read and corrected on 23 Oct 2026. Every numerical final answer is recomputed from the question's own numbers by a calculator check that runs before each release; proofs and explanations were read, not machine-checked. The NCERT textbook is the authority — if something here disagrees with it, follow the book.
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In-text (page 129) Q1
In an asexually reproducing species, trait A is in 10% of the population and trait B in 60%. Which trait probably arose earlier?
- Asexual reproduction produces offspring that are exact copies of the parent, so new traits appear rarely through mutation.
- Once a trait appears in an asexual population, it is passed on to all subsequent generations without change.
- Therefore, a trait that has had more time to spread will be found in a larger percentage of the population.
- Trait B is present in 60% of the population, while trait A is present in only 10%.
- Since trait B is more widespread, it must have arisen earlier and had more time to become common.
- Trait A is likely a newer mutation that has not yet spread to the majority of the population.
Answer: Trait B probably arose earlier.
In-text (page 129) Q2
How does variation in a species promote survival?
- Variation refers to the differences in traits among individuals of the same species.
- When the environment changes, some individuals with specific variations are better suited to survive.
- These better-adapted individuals survive and reproduce, passing their useful traits to the next generation.
- Over many generations, the species accumulates these favorable variations.
- This process, known as natural selection, ensures the species can adapt to new conditions.
- Thus, variation provides the raw material for evolution and long-term survival.
Answer: Variation promotes survival by allowing individuals with favorable traits to survive and reproduce in changing environments, leading to the evolution of the species.
Other exercises in this chapter
- In-text questions (page 133) — 4 questions
- End-of-chapter exercises — 4 questions
← Heredity: notes, practice and all exercises
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