Homologus traits:
For my species that posses homologus traits I chose whales
and humans and their arms and fins. The bones in both the human hand and arm
are similar to the bones that are in the fin of a whale. We humans have five
fingers and even though we cannot see them, whales have five “finger” bones as
well. In addition to those finger bones, both whales and humans have a humerus,
a radius, and an ulna. Humans use their hands and fingers to help us function
on dry land. Whales are in the water so they do not need fingers like humans
do. Their fins function for their environment; if they had fingers underwater
it would slow them down. The common ancestor between these two species would be
the first tetrapod, which scientists believe lived 350 million years ago. It is
believed that in addition to humans and whales, lizards and birds are also
descendants of this one common ancestor.
Photo Courtesy of: World Wildlife Organization
Photo Courtesy of Pace University
Analogous traits:
Two different species that possess analogous traits are
dolphins and sharks. Both are animals who live in the ocean and have similar
features, such as fins, body shape, however many of their features are
analogous and not homologus. They both have fins and swim instead of live on
land. One of their similarities to the naked eye is their shape. Both animals
have a similar shape, however sharks do not have bones rather, they have
cartilage. Dolphins on the other hand have bones. It would seem that both
animals would have similar skeletons not only because they look similar but,
they share the same environment.
It is possible that back in time somewhere these two animals did share a
common ancestor. However, dolphins are mammals and sharks are not. This is a
major difference between the two species.
Since they are not of the same family we know that the traits have
evolved over long periods of time.
Photo Courtesy of: National Geographic Your Voice
Photo Courtesy of: BBC
Sources used:
http://evolution.berkeley.edu/evolibrary/article/0_0_answer=b/similarity_hs_09
http://www.pace.edu/human-resources/
http://www.worldwildlife.org/species/whale
Good description of your homologous traits. Do we really need to go back 350 million years to find a common ancestor with the ancestral trait? Both of these organisms are mammals, so we know they share a common mammalian ancestor who possessed the ancestral mammalian limb structure, passing on this structure to both of these organism. That is all we need to know to confirm these are homologous traits.
ReplyDeleteGood discussion on your analogous trait. You make some assumptions on ancestry that get you into some trouble in your conclusions. Yes, the common ancestor of the dolphin and the shark lived very long ago and yes, one is a mammal and one is a fish. But that isn't sufficient to confirm these are homologs. Our inner ear bones (the tiny ones) evolved from early fish branchial arches. No kidding. They are homologous traits, regardless of there differences in structures and the fact that the ancestor was a fish and we are mammals. Moreover, the common ancestor of the shark and the dolphin was an early fish who possessed this similar fin structure. So could these possibly be homologs?
We know that dolphins are mammals and arose from land mammals who didn't possess this fin structure. That means these are derived traits in dolphins, arising independently from that common ancestor. That is what we need to know to confirm these are analogs.
Good images.
I liked your post your pictures were really useful! Additionally I had fun reading your ideas it was very interesting to consider. I think you also did a wonderful job comparing and contrasting your homologous/ analogous traits
ReplyDeleteGood job with your post. I found your information to be very interesting. It is funny how dolphins and sharks look very similar but are actually very different from each other.
ReplyDeleteI always thought that these two animals were very similar especially in their shape and size so I assumed that they shared a similar ancestor but after reading your post I can now see why they are actually very different. The fact that they both have very different skeletal structures (Dolphins Bone and Sharks Cartilage) is something that I would have never expected and didn’t even know about till just a few minutes ago. But yeah great post!
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