Download Njige Reproduction Full Note For Advance
What is the meaning of term "Reproduction"?
Reproduction: is the biological process by which new organisms of the same species are produced from existing ones.
Types of Reproduction
Living organisms reproduce in two main ways: sexual reproduction and asexual reproduction.
(A) Sexual Reproduction
Sexual reproduction happens when two parents combine their special cells (called gametes) to create offspring that are genetically different from the parents. This is common in most animals and plants.
Steps in sexual reproduction:
1. Gametogenesis: Special cells called gametes (like sperm and eggs) are made through a process called meiosis, which reduces the number of chromosomes by half.
2. Fertilization: The sperm and egg combine to form a zygote with a full set of chromosomes.
3. Development: The zygote grows into an embryo and later becomes a new organism.
4. Birth or Hatching: After development is complete, the new organism is born or hatches.
(B) Asexual Reproduction
Asexual reproduction happens when one parent produces offspring without the need for gametes. The offspring are usually exact copies of the parent.
Types of asexual reproduction:
1. Binary fission: A single organism splits into two identical ones. Example: Bacteria.
2. Budding: A new organism grows as a small part (bud) on the parent and then detaches. Example: Yeast.
3. Fragmentation: The parent breaks into pieces, and each piece grows into a new organism. Example: Tapeworm.
4. Parthenogenesis: An egg develops into an organism without being fertilized. Example: Banana.
5. Vegetative propagation: New plants grow from parts of the parent plant, like stems, roots, or leaves. Examples: Strawberries (runners), potatoes (tubers), and onions (bulbs).
What is the importances of Reproduction?
- Reproduction is essential for the survival of all living organisms.
- It helps increase the number of individuals in a species, ensuring the population continues to grow.
- Sexual reproduction creates genetic differences by combining genetic material from two parents, leading to diversity.
- Reproduction plays a key role in evolution. The genetic differences created through reproduction provide the basis for natural selection, which drives changes in species over time.
For more detailed notes about reproduction, you can download this PDF file specially designed for Advanced Level (A-Level) students.
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