NCERT Solutions for Class 10 Science Chapter 7 How do Organisms Reproduce?

Answer: DNA copying is fundamental to reproduction because DNA contains genetic information passed from parent to offspring. Accurate DNA replication ensures that offspring inherit structural design and traits specific to their species. Biochemical inaccuracies during copying also generate minor variations, which are essential for evolution.

Answer: Variations enable a species to survive extreme environmental changes (such as sudden temperature changes or chemical pollution). While an individual variation might not offer an immediate personal benefit or could even be harmful, genetic diversity across the population prevents total extinction of the species during ecological crises.

Binary Fission: A single parent organism divides into two equal daughter cells under favorable conditions. Example: Amoeba, Paramecium.

Multiple Fission: A single parent organism divides simultaneously into numerous daughter cells within a protective cyst, usually during unfavorable conditions. Example: Plasmodium.

Answer: Spores are protected by thick outer walls that resist extreme environmental conditions like heat, drought, and lack of nutrients. Being lightweight, spores are easily dispersed by air and water across large geographic areas, germinating when they land on favorable moist surfaces.

Answer: The placenta is a specialized disc-like tissue embedded in the uterine wall. It features finger-like villi on the embryo’s side and blood spaces surrounding them on the mother’s side. This design creates a huge surface area for transferring glucose, oxygen, and nutrients from mother to fetus and carrying metabolic waste products from fetus back to mother for excretion.

(a) Amoeba
(b) Yeast
(c) Plasmodium
(d) Leishmania

Correct Answer: (b) Yeast (and also in Hydra).

(a) Ovary
(b) Uterus
(c) Vas deferens
(d) Fallopian tube

Correct Answer: (c) Vas deferens (it is a part of the male reproductive system).

(a) Sepals
(b) Ovules
(c) Pistil
(d) Pollen grains

Correct Answer: (d) Pollen grains.

Answer:

1. Genetic Diversity: Combines genetic material from two distinct individuals, producing variations in every generation.

2. Adaptability & Evolution: Greater variations enhance population survival rates against diseases and changing climates, accelerating evolutionary adaptation.