Summary
Fertilisation is the process where the nuclei of two gametes fuse to form a zygote, marking the beginning of a new individual. This process occurs in both plants and animals, with specific mechanisms involved in each.
- Gametes — sex cells that contain half the genetic information. Example: Sperm and egg cells in animals, pollen and ovules in plants.
- Zona Pellucida — a thick protective layer around the egg cell. Example: It allows selective entry of sperm and prevents multiple fertilizations.
- Acrosome Reaction — release of enzymes from the sperm to penetrate the egg. Example: Helps the sperm penetrate the zona pellucida.
- Cortical Reaction — changes in the egg to prevent entry of additional sperm. Example: Occurs after the sperm penetrates the zona pellucida.
- Pollination — transfer of pollen to the stigma of a flower. Example: First step in plant fertilization.
- Double Fertilization — unique process in flowering plants involving two fertilization events. Example: Formation of zygote and endosperm.
Exam Tips
Key Definitions to Remember
- Gametes
- Zona Pellucida
- Acrosome Reaction
- Cortical Reaction
- Pollination
- Double Fertilization
Common Confusions
- Difference between fertilization in plants and animals
- Role of the zona pellucida in fertilization
Typical Exam Questions
- What is the role of the acrosome reaction? It helps the sperm penetrate the egg's protective layers.
- How does double fertilization occur in plants? It involves the fusion of one male gamete with the egg cell and another with the polar nuclei.
- What prevents multiple sperm from fertilizing the same egg? The cortical reaction changes the zona pellucida to block additional sperm.
What Examiners Usually Test
- Understanding of the fertilization process in both plants and animals
- Differences between sperm and egg cells
- Mechanisms preventing polyspermy