IMPORTANTE: No momento, não há atividades neste fórum. Por favor,caso queira sanar suas dúvidas, visite o fórum ,que você encontrará seções ativas de biologia e química.


Este fórum é um espaço dedicado ao ensino da Biologia e Química que, disponibiliza em suas páginas, apostilas, e-books, questões resolvidas e tudo o mais para incentivar e expandir o aprendizado.

Para abrir Editor LaTeX Codecogs - clique

clique em "copy to document" e copie o código HTML para o campo de postagem
Thank you Codecogs!
CodeCogs - An Open Source Scientific Library

    The penis only evolved once, suggests study of lizard embryos


    Mensagens : 227
    Data de inscrição : 08/06/2015

    The penis only evolved once, suggests study of lizard embryos

    Mensagem por glory1 em Qua Out 28, 2015 10:29 pm

    The adult tuatara lizard (Sphenodon punctatus, seen above) has no penis. But among amniotic animals—reptiles, birds, and mammals—that’s not even that weird. Many snakes have double “hemipenes” and ducks have spiraling phalluses that look like fusilli pasta. This diversity in amniotic genitals has puzzled scientists as they try to map out the evolutionary tree of life. The fact that the tuataras don’t have penises makes them a useful study organism because it allows scientists to ask whether the lizards’ ancestors had penises and lost them, or never had them to begin with. Now, according to new research published today in Biology Letters, the last common ancestor of all the amniotes did, in fact, have an erectable phallus, and that the modern diversity is the result of evolutionary tweaks over time (not the separate evolution of different phalluses). The findings come from an analysis of Victorian-era tuatara embryos preserved on slides at the Harvard Embryological Collection. Scientists used pictures of the lizard embryos to recreate their 3D structure using computer software. The team discovered that, even though the tuatara has no external phallus, it grows the beginnings of one during development. At some point down the line this “genital swelling” recedes and the lizards are born sans phallus. The embryonic development suggests that amniotic penises only evolved once, but that some animals have lost theirs over time.

      Data/hora atual: Dom Mar 24, 2019 1:58 am