Why is it more common to see two heads on some species like turtles or snake than it is to see a two headed shark or lion?
In: Biology
I agree with the other comments. The birth process also has an effect:
The egg is roughly the same shape and size even if the baby snake or turtle inside has extra heads or too many legs. It’s just as easy for the mother to give birth as it would be for a normal egg.
A live birth where the baby has an extra head or extra legs is a bigger and a much more complicated shape for a mother animal to push out of the birth canal. It’s more likely that mother and baby would die during the birth.
Mothers of deformed live-birth babies are more likely to die from it, so they don’t live to have more offspring. Mothers of egg-laying species are less likely to die, so they go on to have more babies, who may have the same defect if it’s genetic.
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