Internal Reproduction

External Reproduction

- Greater chance of fertilisation between sperm and egg so that excess gametes are not wasted.                                            
- More protection against outside environments and predators, and therefore a higher chance of surviving until birth.
- More selective of their mates (natural selection).
-Less chance of desiccation of gametes

- Difficult to find mates in a dwindling population
- Limited amount of offspring being produced at any given time. (e.g. humans cannot carry dozens of children)
- Higher risk of sexually transmitted diseases being passed from one individual to another.

- Many gametes are realeased at one time and there are generally more offspring.
- Easier to find mates as the gametes released can drift (wind, water etc).
- More genetic variation as many different individuals of a species release gametes together.

- Greater chance of desiccation of gametes/zygotes.
- Greater chance of gametes/zygotes exposed to likely predators.
- Not guaranteed that sperm will come in contact with eggs due to variables (e.g strong water currents, unbalanced no. of females/males in the population.
- Large amounts of gametes go unfertilised and wasted.