Understanding:
• Fertilization in animals can be internal or external
External Fertilization
- External fertilization involves the fusion of gametes (egg and sperm) outside of the body of a parent
- It is most common in aquatic animals, where the water acts as a medium via which the gametes can travel
- This method of fertilization is susceptible to environmental influences, such as predators and pH changes
- Consequently, species that reproduce this way usually release large quantities of gametes to compensate for losses
- The process of releasing gametes into the water is called spawning
External Fertilization – Mass Spawning by Coral
Video caption from Jonathan Bird’s Blue World (http://www.blueworldtv.com)
Internal Fertilisation
- Internal fertilization involves the fusion of gametes (egg and sperm) inside of the body of a parent
- This requires a method by which the gamete of one parent can be introduced inside the body of another (e.g. copulation)
- Terrestrial animals typically use internal fertilization so as to prevent exposure and desiccation of gametes or embryos
- Internal fertilization offers more protection to the gametes and embryos, but at a potential survival cost to the parent
Internal Fertilisation – Fusion of an Egg and Sperm