Advantages and Disadvantages of Internal and External Fertilisation

Fertilisation that occurs outside the female body
Gametes are directly shed into the water (not in the female’s body)
Successful in aquatic environments because large numbers of gametes and fertilised eggs can disperse over a wide area, and the gametes would desiccate (dry up) if external fertilisation occurred in a terrestrial environment
Copulation does not occur
Many organisms are involved
Chances of fertilisation are increased by: cyclical reproductive behaviours and synchronised production and release of gametes
Zygote formation occurs outside the female’s body, and there is a lesser chance of it occurring

Avoids the energy of attracting a mate, but millions of gametes are produced for both sexes

Fertilisation that occurs inside the female body
Gametes are directly transferred into the female body
Successful in terrestrial environments because the problem of desiccation is solved as fertilisation occurs in a watery environment inside the female body
Copulation occurs
2 organisms are involved
Zygote development occurs inside the female body and has a higher chance of it occurring
Fertilisation chances are increased by direct transfer of male gamete
Energy is invested in the male attracting a mate, e.g courtship dances however, less energy may be invested in single gamete production for the female (male-produces millions)