External fertilisation is a method of sexual reproduction in which the male and female gametes are deposited into the external environment, where fertilisation occurs and the embryo develops.
Conditions of external fertilisation
This method of reproduction almost exclusively occurs in the aquatic environment, where the environmental conditions are favourable to the meeting of gametes and egg development.
If the parents do not meet, several mechanisms favour the meeting of their gametes: synchronisation of sexual cycles, gatherings of parents, emission of attractive chemical substances, etc.
When toads (amplexus) mate, there is no penetration. Gametes are released into the environment, where fertilisation occurs. © PhOtOnQuAnTiQuE CC by-nc-nd 2.0
External fertilisation - 1 Photo