10th How do organisms Reproduce NCERT Solution

1. Asexual reproduction takes place through budding in

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

Answer: (b) Yeast

Step-by-step reasoning:

1. Budding is a type of asexual reproduction where a new organism grows out of the body of the parent.
2. In yeast, a small protuberance (bud) forms on the parent cell, its nucleus divides, and one nucleus migrates into the bud.
3. The bud enlarges and eventually detaches as an independent yeast cell.
4. Other organisms listed reproduce by binary fission (Amoeba), sporozoite formation (Plasmodium), or other modes (Leishmania).

2. Which of the following is not a part of the female reproductive system in human beings?

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

Answer: (c) Vas deferens

Step-by-step reasoning:

1. Ovary, uterus, and fallopian tube are intrinsic to the female reproductive tract.
2. Vas deferens is a duct that transports sperm in males, not females.

3. The anther contains

• (a) sepals.
• (b) ovules.
• (c) pistil.
• (d) pollen grains.

Answer: (d) pollen grains

Step-by-step reasoning:

1. Anther is part of the stamen (male reproductive organ) of a flower.
2. It produces and houses pollen grains, which carry male gametes.

4. What are the advantages of sexual reproduction over asexual reproduction?

• Generates genetic variation in offspring, enhancing adaptability to changing environments.
• Allows elimination of harmful mutations through recombination and natural selection.
• Promotes evolution of new traits and speciation over generations.
• Reduces buildup of deleterious alleles in a population.

5. What are the functions performed by the testis in human beings?

• Production of spermatozoa (spermatogenesis).
• Secretion of the hormone testosterone, which regulates secondary sexual characteristics, libido, and supports spermatogenesis.

6. Why does menstruation occur?

• In each cycle, rising estrogen and progesterone thicken the uterine endometrium preparing for possible implantation.
• If fertilization does not occur, levels of progesterone and estrogen fall.
• The drop in these hormones triggers breakdown and shedding of the endometrial lining—menstruation.

7. Draw a labelled diagram of the longitudinal section of a flower.

     ___________________________
    |                           |
    |         Stigma            |
    |__________|________________|
               | Style         |
               |_______________|
               | Ovary         |
               |  (with        |
               |   Ovules)     |
    Petal ____/|               |
           /   |               |
     Sepal/    | Receptacle    |
         \     |_______________|
          \    |  Anther       |
    Filament\__|_______________|
             \                 \
              \    Pedicel     \
               \________________\
  

Labels: Sepal, Petal, Anther, Filament, Stigma, Style, Ovary (with ovules), Receptacle, Pedicel

8. What are the different methods of contraception?

• Barrier methods: condom (male/female), diaphragm, cervical cap
• Hormonal methods: oral contraceptive pills, injectables, implants
• Intrauterine devices (IUDs): copper T, hormonal IUD
• Surgical methods: tubectomy (female sterilization), vasectomy (male sterilization)
• Natural methods: rhythm method, withdrawal, basal body temperature

9. How are the modes for reproduction different in unicellular and multicellular organisms?

• Unicellular organisms (e.g., Amoeba, yeast) mainly use asexual reproduction (binary fission, budding, spore formation) to produce clones rapidly.
• Multicellular organisms employ both asexual (e.g., vegetative propagation in plants) and sexual reproduction to generate genetic diversity, ensure tissue specialization, and adapt to complex life cycles.

10. How does reproduction help in providing stability to populations of species?

• Ensures continuity of species by replacing individuals that die.
• Sexual reproduction introduces genetic diversity, which enhances resilience against diseases and environmental changes.
• A balanced mix of asexual and sexual strategies allows rapid population growth when conditions are stable and adaptation when they change.

11. What could be the reasons for adopting contraceptive methods?

• Family planning: to space or limit the number of children.
• Health reasons: to avoid risks of high-risk pregnancies or health complications.
• Economic and social factors: to manage financial resources and improve living standards.
• Population control: to reduce strain on resources and infrastructure at community or national levels.

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