Class 10 – How do Organisms Reproduce

Class 10 Science Chapter 7: Concepts

Chapter 7: How do Organisms Reproduce?

Introduction

All living organisms need to reproduce to continue their species. Reproduction is the process by which organisms produce new individuals of their own kind. It ensures the survival of species and the transfer of genetic information from one generation to the next.

There are two main types of reproduction:

  1. Asexual Reproduction – Involves a single parent and produces offspring that are genetically identical to the parent.
  2. Sexual Reproduction – Involves two parents, leading to genetic variation in offspring.

Asexual Reproduction

Asexual reproduction occurs when a single organism produces offspring without the involvement of gametes (sperm and egg). It is common in single-celled organisms and some simple multicellular organisms.

A. Types of Asexual Reproduction

1. Fission (Binary and Multiple Fission)
  • Binary Fission: A single cell divides into two equal halves.
    • Example: Amoeba, Paramecium, Bacteria
  • Multiple Fission: The nucleus divides multiple times before the cell splits into several daughter cells.
    • Example: Plasmodium (Malaria-causing parasite)
Diagram: Binary Fission in Amoeba
2. Budding
  • A small bud forms on the parent’s body, grows, and eventually detaches as a new individual.
  • Example: Hydra, Yeast
Diagram: Budding in Hydra
3. Fragmentation
  • The parent body breaks into two or more fragments, and each fragment grows into a new organism.
  • Example: Spirogyra (a filamentous alga)
Diagram: Fragmentation in Spirogyra
4. Regeneration
  • The ability to regrow lost body parts or form a complete individual from a part of the parent organism.
  • Example: Planaria (Flatworm), Starfish
Diagram: Regeneration in Planaria
5. Spore Formation (Sporulation)
  • Organisms produce tiny, resistant structures called spores, which develop into new individuals under favorable conditions.
  • Example: Fungi (Rhizopus), Ferns
Diagram: Spore Formation in Rhizopus
6. Vegetative Propagation (In Plants)
  • New plants grow from roots, stems, or leaves of the parent plant.
  • Example:
    • Stem Cutting: Rose, Sugarcane
    • Roots: Sweet potato
    • Leaves: Bryophyllum (small buds grow on leaves)
Diagram: Vegetative Propagation in Bryophyllum

Sexual Reproduction

Sexual reproduction involves the fusion of male and female gametes, leading to variation in offspring. It is common in higher plants and animals.

A. Why Sexual Reproduction?

  1. Produces genetic variation, leading to better adaptability.
  2. Helps in the survival of species by preventing harmful mutations.

Sexual Reproduction in Plants

Flowering plants reproduce sexually through flowers, which contain reproductive organs.

A. Structure of a Flower

A typical flower has four parts:

  1. Sepals: Green outer parts that protect the flower bud.
  2. Petals: Colored structures that attract pollinators.
  3. Stamens (Male Reproductive Organ):
    • Anther (produces pollen)
    • Filament (supports the anther)
  4. Carpel (Female Reproductive Organ):
    • Stigma (receives pollen)
    • Style (connects stigma to ovary)
    • Ovary (contains ovules, which develop into seeds)
Diagram: Structure of a Flower

B. Pollination

Pollination is the transfer of pollen from an anther to a stigma. It can be:

  • Self-Pollination: Pollen from the same flower fertilizes the ovule.
  • Cross-Pollination: Pollen from one flower fertilizes another flower.

C. Fertilization in Plants

  1. Pollen lands on the stigma.
  2. A pollen tube grows down into the ovary.
  3. The male gamete (sperm) fuses with the female gamete (egg) inside the ovule.
  4. The fertilized ovule becomes a seed, and the ovary develops into a fruit.
Diagram: Fertilization in Plants

Sexual Reproduction in Humans

Human reproduction involves the male and female reproductive systems.

A. Male Reproductive System

Diagram: Male Reproductive System

B. Female Reproductive System

Diagram: Female Reproductive System

Fertilization and Development in Humans

  1. The sperm from the male meets the egg in the fallopian tube.
  2. Fertilization occurs, forming a zygote.
  3. The zygote divides and forms an embryo, which implants in the uterus.
  4. The embryo grows into a fetus, nourished by the placenta.
  5. After 9 months, the baby is born.
Diagram: Human Fertilization and Development

Menstrual Cycle

The menstrual cycle prepares the female body for pregnancy. It lasts about 28 days and involves:

  1. Egg release (Ovulation) around day 14.
  2. If fertilization does not occur, the uterus lining sheds (menstruation).
  3. The cycle repeats.
Diagram: Menstrual Cycle
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