Homology and Analogy
- Koalas and Kangaroos both have marsupiums (pouches) . Kangaroos are found in Australia and have powerful legs and feet that have adapted for leaping. The Koala is also found in Australia and has thick coat, large ears, long limbs and sharp claws.
- Both species use their marsupium as means for postnatal care of their offspring. After giving birth, the offspring travel to the pouch for further development and nutrition. The koala marsupium has two teats, and is upside down, while a kangaroo’s marsupium has four teats and is right side up. It’s interesting to note that the koala’s upside down marsupium enables the joey to feed on the mother’s droppings that contain special nutrition for the young.
- Although the exact species name for the most recent common ancestor of the koala and kangaroo are unknown, we know they split from mammals about 130 million years ago.
- Humans (homo sapien) and American Alligators(alligator mississippiensis) both posses an analogous trait that can be seen in the structure of the arm. Humans are mammals, have the ability to stand up right and are the only living species of the genus “homo”. American Alligators are reptiles usually known for their strong jawsand lives in freshwater swamps, marshes, lakes and rivers. An adult alligator weighs about 800 pounds and is about 13 feet long, where as an adult human is usually 150 to 180 pounds and about five to six feet tall.
- Both Humans and American Alligators share analogous traits in their radius, ulna, humerus, and carpals. An Alligator uses his forelegs mainly for transportation on land, while a Human arm has multiple uses and is not primarily used as a way to transport himself on dry land. A human may use his arm to swim in water, but an alligator uses his tail not his forelegs to swim.
- The common ancestor between humans and alligators are Devonian Fish about 417 million years ago. Devonian Fishes did not have forearms but had fins, as forearms would not prove useful underwater. It was not until the fish diverged into two categories, fish and reptile that forearms became present.
I like your examples of the homologus traits. Yu did a good job of explaining the differences of the traits on each animal. I would have never thought an alligator and human had similar arm bones but now it makes sense. You did a good job of tracing the ancestor and placing the change that brought the trait on.
ReplyDeleteI really like your comparison of the koala and the kangaroo in your homologous comparison. Its very interesting how close both marsupiums are a like. What really interested me is that the koalas is actually upside down.
ReplyDeleteI like your choice for a homologous trait in comparing koalas and kangaroos. Marsupials are an original species of mammal and it’s very interesting how they give birth. The fact that they are only found in Australia may also be an example of geographical isolation. I also thought that your choice for an analogous trait in comparing the structure of limbs in humans and alligators was very original.
ReplyDeleteGreat job on the koala and kangaroo. I know it's not very anthropological but, yuck!, with regard to the droppings. :-)
ReplyDeleteThe limb structure of humans and alligators are actually homologs. The reason we share the same kind of bones is because we inherited our limbs and skeletal structure from a common ancestor, which was actually another earlier reptile.
That interesting that you chose a trait as general as arms. For my blog I was looking for unique, specific traits like fins and blow holes - which is waht I used. Being in anthro pology definitely provides a new scope on what is normal and unique.
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