martes, 10 de enero de 2017

Does laying eggs or not laying eggs have any impact on flying animals?

What are the chances that an animal which does not lay eggs will one day evolve into a flying animal? Does laying eggs or not laying eggs impact the survival chances of flaying animals?

Not being particularly amused by our own way or reproduction, and I talk from my own experience, I mean I don't belong to the supermammy supermammal party, I'll try to give an objetive answer to this question, and fisnish it before it comes too long and boring.
Evolutively speaking eggs came first, before than oviparity and fliying. Powered flight has appeared only 4 times in the history of animals: insects, peterosauros, birds and bats, see Flying and gliding animals for a longer explanation (interestingly enough 3 of them in vertebrate animals).  Vivipary has appeared more than once as well, with different hints it has been reported in some frogs (there are cases of ovoviviparity and hemotrophic viviparity), salamanders and sharks (histotrophic viviparity), and of course in all mammals excepting monotremes. There are also many cases of viviparity in plants.

  • In flying insects the rule is oviparity, although there is an orden of true flies that exhibit a form of viviparity, so we can study gravid flies, for example in the tse-tse fly. (Adenotrophic viviparity).
  • (A gravid tse-tse fly: Adenotrophic viviparity).
  • All pterosaurus described to this date were oviparous.
  • All birds are oviparous.
  • All flying mammals, i.e the almost 1,000 species of bats, are viviparous.

So this trend clearly points to two conclussions:

- There is a significant higher chance of flying occurring among oviparous animals than in viviparous ones. And very probably due to that viviparity imposes some restrictions to the development of flight, given that it is (on average) more exigent in natural resources than viviparity. Although there are cases of oviparous animals that have turned viviparous after having acquired flight, like the tse-tse. But exceptions are the rule in nature!.
- It is possible to acquire power flight for an obliged viviparous animals, and thrieve, there are the bats to prove it. But in general, bat flight is more energy demanding than bird flight and thy are in slight disadvantadge in front of birds.

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