Yes
what two classes of vertebrates use external fertilisation
frogs use external fertilisation so the sperm is released into the water and the eggs are are released into water then the sperm fertilises the eggs
spiders
Yes.
yes,sometimes
Lions are mammals, and use internal fertilisation.
Frogs use external fertilisation, this means that the female frog lays thousands of eggs, but then the male sprays sperm on the offspring to fertilise it. So basically the sperm cell and egg cell meet when the male sprays his sperm cells over the eggs.
don't know external gills
Most fish use external fertilization. But not all, guppies and other livebearers use internal fertilization. Of the external fertilizers, some are broadcast spawners, whereas others are not.
The frogs that I've heard about use external fertilization. In other words, the female lays her eggs, and then the male fertilizes them.
Marine mammals have internalized genitalia for streamlining.
Mainly fishes are living in water and they are not having the proper fertilization system in side its structure, so they prefer external fertilization process.