32 Birds and mammals share a common ancestor. The ancestor of these two classes was a terrestrial vertebrate. Today some

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32 Birds And Mammals Share A Common Ancestor The Ancestor Of These Two Classes Was A Terrestrial Vertebrate Today Some 1 (896.08 KiB) Viewed 42 times

32 Birds and mammals share a common ancestor. The ancestor of these two classes was a terrestrial vertebrate. Today some species in both groups spend large amounts of time in an aquatic environment. Two such species are penguins and seals. The hypothesised evolution of both of these groups is shown in the phylogenetic tree below. coelacanth -platypus kangaroo seal human -python lizard turtle crocodile ostrich penguin - pigeon The last common ancestor of penguins and seals was a vertebrate that lived some time between 305 and 340 million years ago. Evidence suggests that, like modern reptiles, this organism was ectothermic. a Penguins and seals are both endothermic. Explain what kind of evolution has resulted in the two groups having this characteristic. b Discuss why there is so much uncertainty about when the last common ancestor of penguins and seals lived. c Seals and penguins both have forelimbs modified as flippers. These flippers can be considered both homologous and analogous. Explain how both can be correct.