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Question Question 2
Binary Fission and Multiple Fission
| Sl. No. | Binary Fission | Multiple Fission |
|---|---|---|
| 1. | In Binary Fission, a unicellular organism divides into two daughter cells of roughly equal size. | In Multiple Fission, a unicellular organism repeatedly divides inside the cyst to produce many daughter cells. Later the cyst breaks open releasing new organism. |
| 2. | Two daughter cells are produced. | Many daughter cells are formed. |
| 3. | Occurs in normal conditions. | Occurs in unfavourable conditions. |
BRIGHT TUTORIALS
BRIGHT TUTORIALS
ICSE Class VIII | Academic Year 2026-2027
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Biology | Chapter 5: Reproduction in AnimalsWeb Content
Reproduction in Animals – Interactive Study Guide
Quick Overview
Reproduction ensures the continuation of species. Animals reproduce sexually (fusion of gametes) or asexually (single parent, no gametes). This chapter also covers embryo development and cloning.
Sexual vs Asexual Reproduction
| Feature | Sexual | Asexual |
|---|---|---|
| Parents | Two (male + female) | One |
| Gametes | Required (sperm + egg) | Not required |
| Offspring | Genetically different (variation) | Genetically identical (clones) |
| Examples | Humans, frogs, birds | Amoeba, Hydra, yeast |
Fertilisation Types
Internal
Inside female body. Fewer eggs, better protection. Examples: humans, birds, dogs.
External
Outside body (in water). Many eggs, lower survival. Examples: frogs, fish, starfish.
Development Sequence
Zygote → Embryo → Foetus → Baby
Zygote (1 cell) divides → Embryo (ball of cells, implants in uterus) → Foetus (recognisable body parts) → Birth (~9 months in humans)
Nutrition via placenta through umbilical cord.
Asexual Reproduction Types
Summary
- Budding: Bud grows from parent → detaches (Hydra, yeast)
- Binary fission: Parent splits into 2 equal parts (Amoeba, bacteria)
- Fragmentation: Body breaks into fragments, each grows (Planaria, starfish)
Cloning: Dolly the Sheep
Key Facts
First cloned mammal (1996). Ian Wilmut, Roslin Institute, Scotland. Nucleus from donor cell → enucleated egg → embryo → surrogate mother → Dolly (genetic copy of donor).
Self-Test Questions
Test Yourself
- What is the difference between internal and external fertilisation?
- Differentiate between viviparous and oviparous animals with examples.
- Describe binary fission in Amoeba.
- What is IVF? Why is it called "test-tube baby"?
- How was Dolly the sheep cloned?