BIOLOGY- REPRODUCTION IN ORGANISM Part 4

BIOLOGY- REPRODUCTION IN ORGANISM Part 4

Biology: Reproduction in Organisms – Part 4

Reproduction in Organisms

Reproduction is a biological process by which organisms produce their offspring. It ensures the continuity of species.

Part 4: Sexual Reproduction in Organisms

1. What is Sexual Reproduction?

Sexual reproduction involves the fusion of male and female gametes (sperm and egg) to form a zygote, which develops into a new organism.

• Biparental Inheritance: Involves two parents.
• Genetic Variation: Offspring show variations due to recombination of genes.

2. Phases of Sexual Reproduction:

1. Pre-fertilization Events:

   • Gametogenesis: Formation of male and female gametes.
     • Isogamy: Similar gametes (Algae).
     • Anisogamy: Dissimilar gametes (Humans).
   • Gamete Transfer: Transfer of gametes for fertilization.

2. Fertilization (Syngamy):

   • External Fertilization: Fusion occurs outside the body (Fishes, Amphibians).
   • Internal Fertilization: Fusion occurs inside the body (Reptiles, Mammals).

3. Post-fertilization Events:

   • Zygote Formation: Fusion of sperm and egg forms a zygote.
   • Embryogenesis: Development of the embryo from the zygote.

3. Types of Organisms Based on Reproduction:

• Oviparous: Egg-laying organisms (Birds, Reptiles).
• Viviparous: Give birth to young ones (Humans, Mammals).
• Ovoviviparous: Eggs hatch inside the mother’s body (Some Sharks).

4. Importance of Sexual Reproduction:

• Creates genetic diversity.
• Helps in adaptation and evolution.
• Reduces the accumulation of harmful mutations.

5. Examples of Sexual Reproduction:

• Plants: Pollination and fertilization lead to seed formation.
• Animals: Fertilization between sperm and egg.

 Quick Quiz:

1. What is the difference between isogamy and anisogamy?
2. Name one oviparous and one viviparous animal.
3. Why is genetic variation important in sexual reproduction?

अगर आपको किसी और टॉपिक या डिटेल्स में जाना है तो बताइए!

BIOLOGY- REPRODUCTION IN ORGANISM Part 4

CHAPTER – How do Organisms Reproduce?

Reproduction-in-organisms.pdf

NCERT-Class-12-Biology.pdf

REPRODUCTION AND POPULATION CONTROL

Here is Part 4 of the Biology – Reproduction in Organisms chapter, based on NCERT Class 12 syllabus and general biology topics:

Biology – Reproduction in Organisms (Part 4)

Topic: Reproductive Structures and Events in Sexual Reproduction

1. Overview of Sexual Reproduction

Sexual reproduction involves the fusion of male and female gametes (haploid) to form a zygote (diploid), which develops into a new organism.

It occurs in three phases:

1. Pre-fertilization Events

2. Fertilization

3. Post-fertilization Events

2. Pre-fertilization Events

These events happen before fertilization and include:

(a) Gametogenesis – Formation of gametes

• Male gamete: Sperm (in animals), Pollen (in plants)

• Female gamete: Ovum (in animals), Egg cell (in plants)

Types of gametes:

• Isogametes – morphologically similar (e.g., algae)

• Anisogametes – morphologically different (e.g., human)

(b) Gamete Transfer

• In animals: Male delivers sperm to the female via copulation (internal) or external release (in aquatic species).

• In plants: Pollen grain is transferred to stigma (pollination).

3. Fertilization (Syngamy)

• It is the process of fusion of male and female gametes to form a zygote.

• Types:

  • External Fertilization – outside the body (e.g., frog, fish)

  • Internal Fertilization – inside the body (e.g., humans, birds)

Importance:

• Restores diploid number.

• Initiates development of the new organism.

4. Post-fertilization Events

(a) Zygote Formation

• Zygote is diploid (2n) and develops into an embryo.

• In higher organisms, zygote undergoes mitosis.

(b) Embryogenesis – Development of embryo

• Cell division (cleavage) and cell differentiation occur.

• In animals:

  • Oviparous: Lay eggs (e.g., birds, reptiles)

  • Viviparous: Give birth to young ones (e.g., mammals)

• In plants:

  • Zygote remains in ovule → develops into embryo

  • Ovule becomes seed, and ovary becomes fruit

Summary Table:

Quick Quiz:

1. What is anisogamy?

2. Where does fertilization occur in humans?

3. What does ovary convert into after fertilization?

Answers:

1. Fusion of dissimilar gametes

2. In fallopian tubes (oviduct)

3. Fruit

Would you like Part 5: Asexual vs. Sexual Reproduction Comparison, or a PDF revision sheet?

BIOLOGY- REPRODUCTION IN ORGANISM Part 4

CBSE Class 12 Biology – Cloudfront.net

Class XII Chapter 1 – Reproduction in Organisms Biology