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Gametes & Fertilisation (Cambridge O Level Biology)
Revision Note
Gametes & Fertilisation
- Fertilisation is the fusion of the nuclei from a male gamete (sperm cell) and a female gamete (egg cell)
- It occurs in the oviducts
- This results in the formation of a zygote which will undergo cell division and grow to form an embryo
- Gametes have adaptations to increase the chances of fertilisation and successful development of an embryo
Adaptations of Gametes
| Gamete | Adaptive feature | Reason |
| Sperm | Has a flagellum (tail) | Enables it to swim to the egg |
| Contains enzymes in the head region (acrosome) | To digest through the jelly coat and cell membrane of an egg cell when it meets one | |
| Contains many mitochondria | Provide energy from respiration so that the flagellum can move back and forth for locomotion | |
| Egg | Cytoplasm containing a store of energy | Provides energy for the dividing zygote after fertilisation |
| Jelly-like coating that changes after fertilisation | Forms an impenetrable barrier after fertilisation to prevent other sperm nuclei entering the egg cell |
Comparison of Male & Female Gametes Table
| Sperm | Egg | |
| Size | Very small (45µm) | Large (0.2mm) |
| Structure | Head region and flagellum, many structural adaptations | Round cell with few structural adaptations, covered in a jelly coating |
| Motility | Capable of locomotion | Not capable of locomotion |
| Numbers | Produced every day in huge numbers (around 100 million per day) | Thousands of immature eggs in each ovary, but only one released each month |
Comparing sperm and egg cells
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