Day: January 17, 2025

Looking for solved exercises for Chapter 10: Reproduction? Our comprehensive solutions are specifically designed for 9th Class students based on the updated 2025 syllabus. Simplified answers to key topics like binary fission, vegetative propagation, and the life cycle of flowering plants are included to make your preparation easier and more efficient.

---

MCQs with Solutions

1. Which of the following organisms commonly reproduce by binary fission?

• Options:
  a) Yeast
  b) Bacteria
  c) Rhizopus
  d) Plants
• Answer: b) Bacteria
• Explanation: Binary fission is a simple asexual reproduction method where a single cell divides into two identical daughter cells. This process is typical in prokaryotic organisms like bacteria.
• Tip/Trick: Remember that binary fission is exclusive to unicellular organisms like bacteria.

---

2. What is the primary method of reproduction in yeast?

• Options:
  a) Binary fission
  b) Spore formation
  c) Budding
  d) Fragmentation
• Answer: c) Budding
• Explanation: Yeast, a unicellular fungus, reproduces primarily by budding, where a new cell forms as an outgrowth of the parent cell.
• Tip/Trick: Associate yeast with budding since it involves a “bud” growing on the parent cell.

---

3. Which of the following statements is true about spore formation in fungi?

• Options:
  a) They produce spores during sexual reproduction.
  b) They produce two kinds of spores.
  c) Spores can only grow into new fungi in dry environments.
  d) Spores are produced to withstand harsh conditions.
• Answer: d) Spores are produced to withstand harsh conditions.
• Explanation: Spores in fungi are designed to survive extreme environmental conditions, including dryness, heat, or lack of nutrients.
• Tip/Trick: Focus on “harsh conditions” when considering the purpose of fungal spores.

---

4. What happens in some bacteria during harsh conditions?

• Options:
  a) Creation of a bud that detaches from the cell.
  b) Formation of thick-walled endospores.
  c) Splitting the cell into two identical daughter cells.
  d) Fusion of two bacterial cells.
• Answer: b) Formation of thick-walled endospores.
• Explanation: Endospores are highly resistant structures formed by bacteria to protect their genetic material during unfavorable conditions.
• Tip/Trick: Recall that endospores = bacterial survival strategy.

---

5. Which of the following is an example of vegetative propagation through runners?

• Options:
  a) Potato
  b) Strawberry
  c) Onion
  d) Ginger
• Answer: b) Strawberry
• Explanation: Strawberries propagate vegetatively through runners, which are horizontal stems that grow along the soil’s surface and develop new plants.
• Tip/Trick: Think of “running strawberries” for runners.

---

6. Which plant propagates through tubers?

• Options:
  a) Onion
  b) Potato
  c) Ginger
  d) Garlic
• Answer: b) Potato
• Explanation: Tubers are thickened underground stems, such as potatoes, that store food and enable vegetative propagation.
• Tip/Trick: Visualize a potato’s “eyes” as propagation points.

---

7. The horizontal aboveground stem, which produces leaves and roots at its nodes:

• Options:
  a) Stolon
  b) Bulb
  c) Rhizome
  d) Corm
• Answer: a) Stolon
• Explanation: Stolons are horizontal stems that grow above the ground and help plants like strawberries propagate.
• Tip/Trick: Stolons are “above-ground runners.”

---

8. Which of these does NOT help a plant in vegetative propagation?

• Options:
  a) Rhizome
  b) Corm
  c) Runner
  d) Flower
• Answer: d) Flower
• Explanation: Flowers are reproductive structures for sexual reproduction, not vegetative propagation.
• Tip/Trick: Vegetative propagation relies on structures like stems, roots, and leaves, not flowers.

---

9. Which part of the flower is responsible for producing pollen?

• Options:
  a) Stigma
  b) Anther
  c) Ovary
  d) Petal
• Answer: b) Anther
• Explanation: The anther is a part of the stamen in flowers and is responsible for producing and releasing pollen grains.
• Tip/Trick: Associate “anther” with “pollen production.”

---

10. Which of the following is NOT a part of the carpel?

• Options:
  a) Filament
  b) Style
  c) Stigma
  d) Ovary
• Answer: a) Filament
• Explanation: The carpel (or pistil) is the female reproductive part of the flower and consists of the stigma, style, and ovary. The filament is a part of the stamen, the male reproductive structure.
• Tip/Trick: Remember the carpel components as “SOS” — Stigma, Ovary, Style.

---

11. Which structure forms the female gametophyte in flowering plants?

• Options:
  a) Pollen grain
  b) Ovule
  c) Anther
  d) Sepal
• Answer: b) Ovule
• Explanation: The ovule in flowering plants develops into the female gametophyte, which contains the egg cell and is involved in reproduction.
• Tip/Trick: The ovule = female gametophyte, while pollen grain = male gametophyte.

---

12. The male gametophyte in flowering plants is known as:

• Options:
  a) Pollen grain
  b) Embryo sac
  c) Ovary
  d) Carpel
• Answer: a) Pollen grain
• Explanation: The pollen grain is the male gametophyte, carrying the male reproductive cells (sperm). It fertilizes the ovule during pollination.
• Tip/Trick: Associate “pollen” with “male” and “grain” with small particles.

---

13. In the life cycle of flowering plants, which structure is triploid (3n)?

• Options:
  a) Egg
  b) Fusion nucleus
  c) Endosperm nucleus
  d) Sperm
• Answer: c) Endosperm nucleus
• Explanation: The endosperm nucleus is triploid (3n) as it forms after the fusion of one sperm with two polar nuclei during double fertilization.
• Tip/Trick: Triploid = three sets of chromosomes, found in endosperm for nutrient storage.

---

14. Embryo sac is formed inside:

• Options:
  a) Filament
  b) Anther
  c) Style
  d) Ovule
• Answer: d) Ovule
• Explanation: The embryo sac is the female gametophyte and is located inside the ovule of flowering plants.
• Tip/Trick: Embryo sac = female gametophyte = ovule.

---

15. Double fertilization involves:

• Options:
  a) Fertilization of the egg by two male gametes.
  b) Fertilization of two eggs in the same embryo sac by two sperms.
  c) Fertilization of the egg and the fusion nucleus by two sperms.
  d) Fertilization of the egg and the tube cell by two sperms.
• Answer: c) Fertilization of the egg and the fusion nucleus by two sperms.
• Explanation: In double fertilization, one sperm fertilizes the egg to form a zygote (2n), while the other sperm fuses with two polar nuclei to form the endosperm nucleus (3n).
• Tip/Trick: Think “double duty” — one sperm for the egg, the other for the polar nuclei.

---

Short Questions with Detailed Answers

1. Write a short note on budding in yeast.

• Answer: Budding in yeast is a form of asexual reproduction. A small bud grows on the parent cell, enlarges, and eventually detaches to form a new yeast cell. This process ensures rapid multiplication under favorable conditions.

---

2. Write a short note on spore formation in fungi.

• Answer: Spore formation in fungi is an asexual reproduction method where spores are produced inside a sporangium. These spores are resistant to harsh environmental conditions and germinate to form new fungi when conditions are favorable.

---

3. What are the advantages of spore formation in fungi and bacteria?

• Answer:
  • Advantages:
    1. Allows survival in unfavorable conditions due to spore resistance.
    2. Enables rapid reproduction and dispersal over large areas.
    3. Requires minimal resources for reproduction.

---

4. Describe how vegetative propagation occurs through runners.

• Answer: Runners are horizontal stems that grow above the ground. Nodes on these stems produce roots and shoots, which develop into new plants. This is commonly seen in plants like strawberries.

---

5. State how potatoes reproduce through tubers.

• Answer: Potatoes reproduce vegetatively through tubers, which are swollen underground stems. “Eyes” on the tubers sprout into new shoots and roots, growing into new potato plants.

---

6. Describe the advantages and disadvantages of vegetative propagation.

• Answer:
  • Advantages:
    1. Produces genetically identical offspring.
    2. Quick and efficient reproduction.
    3. No need for seeds or pollination.
  • Disadvantages:
    1. No genetic diversity, making plants susceptible to diseases.
    2. Overcrowding can occur, leading to competition for resources.

---

7. Name the four whorls present in a flower and their components.

• Answer:
  1. Calyx: Made of sepals, protects the flower bud.
  2. Corolla: Made of petals, attracts pollinators.
  3. Androecium: Made of stamens, produces pollen.
  4. Gynoecium: Made of carpels, contains ovules.

---

8. Briefly describe the formation of the egg cell and polar nuclei within the embryo sac of a flower.

• Answer: The embryo sac forms inside the ovule during megasporogenesis. One megaspore divides to form eight nuclei, which organize into cells, including the egg cell (near the micropylar end) and two polar nuclei (in the center of the sac).

---

9. Differentiate between:

• i. Asexual and sexual reproduction:
  • Asexual: Single parent, no gametes, offspring identical.
  • Sexual: Two parents, gametes involved, offspring genetically diverse.
• ii. Binary fission in bacteria and amoeba:
  • Bacteria: Simple splitting without a nucleus.
  • Amoeba: Nucleus divides first, followed by cytoplasm.
• iii. Stolon and rhizome:
  • Stolon: Horizontal above-ground stem.
  • Rhizome: Horizontal underground stem.
• iv. Bulb and corm:
  • Bulb: Modified stem with fleshy leaves (e.g., onion).
  • Corm: Solid, fleshy underground stem (e.g., taro).

---

C. Write answers in detail

1. Explain the process of binary fission in bacteria and describe how it leads to the formation of two daughter bacteria.
Binary fission is the process by which bacteria reproduce. In this process:

• The bacterial cell grows and its DNA (genetic material) is copied.
• The cell divides into two parts, with each part getting one copy of the DNA.
• This results in two identical daughter bacteria.

2. What do you mean by vegetative propagation? Differentiate among different plant structures modified for vegetative propagation.
Vegetative propagation is a way plants reproduce without seeds. New plants grow from parts like roots, stems, or leaves of the parent plant.

• Modified roots: Examples are sweet potato and carrot.
• Modified stems: Examples are potato (tuber) and ginger (rhizome).
• Modified leaves: An example is Bryophyllum, where buds grow on leaves.

3. Describe the ways by which humans can grow new plants by using the vegetative parts of the parent plants.
Humans grow new plants using methods like:

• Cutting: A part of a plant like a stem or leaf is cut and planted to grow into a new plant. Example: rose.
• Grafting: Two plants are joined together so they grow as one. Example: mango.
• Layering: A branch of a plant is bent to the ground and covered with soil. It grows roots and becomes a new plant. Example: jasmine.

4. Define sporophyte and gametophyte. State their roles in the life cycle of plants.

• Sporophyte: The part of the plant that produces spores. It is usually larger, like the main body of a plant.
• Gametophyte: The part that produces gametes (sperm and egg cells). It is smaller and often hidden.
  These two alternate in the life cycle of plants. Spores from the sporophyte grow into gametophytes, and gametophytes create gametes that form a new sporophyte.

5. Explain the life cycle of flowering plants, focusing on the alternation between the gametophyte and sporophyte generations.
The life cycle of flowering plants has two stages:

• Sporophyte stage: The main plant that produces flowers and seeds. It creates spores.
• Gametophyte stage: The spores grow into tiny structures inside the flower, which produce male and female gametes.
  When the gametes fuse (fertilization), a seed forms, and the cycle starts again.

6. Describe how the female gametophyte (embryo sac) develops within the ovule of a flower.

• Inside the ovule of a flower, a cell divides to form a structure with 8 nuclei.
• This structure becomes the embryo sac, which is the female gametophyte.
• The embryo sac has one egg cell, which combines with sperm during fertilization to form a seed.

---