Define external fertilisation. Mention its disadvantages:
The fertilisation in which the fusion of gametes occurs outside the body of the female in an external medium, i.e. water, is called external fertilisation. Examples. Bony fishes, amphibians, etc. Organisms that exhibit external fertilisation show great synchrony between the sexes in order to liberate the gametes at the same time. Disadvantages of external fertilisation: A large number of gametes are produced to ensure fertilisation, thus there is wastage. The offspring formed are extremely vulnerable to predators, thus threatening their survival up to adulthood.
