internally because they need time to hatch them
Most fish eggs develop outside of the body. There are however around 3% of all fish which fertilize internally.
GiraffesElephantsRhinosPenguinsOrangutansWhalesSnakesTurtlesChickenMosquito
Birds develop internally, which means inside the creatures body.
They fertilize internally! Many animals reproduce through internal fertilization. A male and female pair up and mate, and the female's eggs are fertilized inside her body. Empid flies mate in this way. The male empid fly is smaller than the female and risks being eaten during mating. To protect himself, he presents the female with a small insect to distract her. More information can be found at the following web address: http://www.infoplease.com/dk/science/encyclopedia/reproduction.html#ESCI309FERTIL
Penguins appear to have very short legs and no knees because only the lower leg is externally visible. Their knees and upper legs are feather covered.
internally
externally
internal
That depends on the species you are asking about, mammals fertilize internally and fish externally.
Guppies are fertilised internally they are livebearers.
Amphibians fertilize their eggs externally.
Koalas do not fertilize their young. They fertilize each other (internally) to produce young.
A deer is a mammal, so reproduction is done internally.
Internal fertilization
true
No. Fishes fertilize externally.
Most fish eggs develop outside of the body. There are however around 3% of all fish which fertilize internally.