many offspring as eggs, and the mother cannot provide and obtain enough resources for a larger amount of offspring. Fish Some species of fish like guppies have the ability to internally fertilize, this process happens by the male inserting a tubular fin into the female’s reproductive opening and then will deposit sperm into her reproductive tract. There are other species of fish that are mouthbrooders which means that one fish puts the eggs in its mouth for incubation. A certain type of fish that is a mouthbrooder is called cichlids and many of them are maternal mouthbrooders. The process for this is the female would lay the egg and pick it up in her mouth. Then the males will encourage the female to open her mouth so they can fertilize the eggs while it’s in the female’s mouth. Internal fertilization in cartilaginous fishes contains the same evolutionary origin as reptiles, birds, and mammals that internally fertilize. Also in these internally fertilizing fish while the sperm is transferred to the reproductive tract there is no noticeable change in tonality. Amphibians Most amphibians have external fertilization but there is an exception to some like salamanders which mostly have internal fertilization. Salamanders do not use intercourse for sexual reproduction due to their lack of external penis. Rather, the male salamander produces an encased capsule of sperm and nutrients called a spermatophore. The male deposits a spermatophore on the ground and the female will pick it up with her cloaca (a combined urinary and genital opening) and fertilize her eggs with it. Over time amphibians have been found evolving to increasing internal fertilization. Within amphibians, it is common for high vertebrates to internally fertilize because of the transition from water to land during vertebrate evolution. There is an advantage for the amphibians who are internally fertilizing allowing for the selection of a time and place for reproduction. Birds Most birds do not have penises, but achieve internal fertilization via cloacal contact (or “cloaca kiss”). In these birds, males and females contact their cloacas together, typically briefly, and transfer sperm to the female. However, water fowls such as ducks and geese have penises and are able to use them for internal fertilization. While birds have internal fertilization, most species no longer have phallus structures. This makes them the only vertebrate taxon to fall into both categories of lacking the phallus but participating in internal fertilization.