Question 4
Describe different types of pollination.
Pollination can be either Natural or Artificial.
Natural Pollination
Natural Pollination is of two types —
- Self pollination — The process of transfer of pollen grains from the anthers to the stigma of the same flower, or another flower of the same plant is called self pollination.
- Cross pollination — The process of transfer of pollen grains from the anthers of a flower to the stigma of a flower of another plane of the same species is called cross pollination. Depending on the external agents involved, cross pollination is classified as Pollination by insects(entomophily), Pollination by wind(anemophily), pollination by water(hydrophilly) and Pollination by animals.
Artificial Pollination
Artificial pollination is performed by experts to produce new varieties of plants having desired characteristics. In this process two different varieties of a plant are selected and artificially pollinated to get a hybrid variety of that species. This is called hybridization.
Reproduction in Animals – Interactive Study Guide
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
Inside female body. Fewer eggs, better protection. Examples: humans, birds, dogs.
Outside body (in water). Many eggs, lower survival. Examples: frogs, fish, starfish.
Development Sequence
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
- 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
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
- 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?