Thursday, November 4, 2010
Homologous and Analogous Traits
For homologous traits I chose to use the example of a human arm and the wing of a bat. Like the human hand, a bats wing has a thumb and finger bones. However the bat has a thin membrane extending from the body and hand and between each finger bone. The human arm/hand of course does not. Much as we use our hands, the bat also uses its fingers, especially thumb to climb. A common ancestor of the bat and human would be the stem reptile, which had a vertebral column and similar bone structures.
For analogous traits I chose to use the example of a human eye and an octopus eye. Both humans and octopuses evolved what is referred to as camera eyes. Its called camera eye because it consists of a lens projecting an image onto a retina. The common ancestor of the octopus and of man possessed this analogous trait and adapted it so it could see.
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Nicely laid out and well-argued until you came down to the statement that the ancestor of the human and the octopus had this trait. That would make it homologous trait if that were the case. Analogous traits due to similar environmental stresses, not to inheritance from a common ancestor.
ReplyDeleteI really liked this post. I don't think I have ever seen a bat skeleton before and would never have noticed the similarity in the bones vs. a human arm/hand. It's really neat to learn how everything that lives and has died is connected in some way. Evolution is a great thing. It helps us survive and keeps things far from being boring. Also I did my blog on Whales, hippos and pigs this week. It was nice to see the whale skeleton in with your bat and human findings. So the whales have little(BIG) hands under those fins, huh? Very neat. Thanks for sharing!
ReplyDeleteThats a very funny way of putting about the whales hands Christi.
ReplyDeleteProf Rodriguez, I guess when you put like that I didn't quite make much sense. I see that now. Thank you.
ReplyDeleteI like the homologus example of a human arm and a bat wing. I also like the pictures you provided. I also find it interesting that you chose a human eye and a octopus eye for the anologus trait. Its very surprising after doing this assignment to see the similiarities that lie within very different species and animals.
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