In the mid-1800s, anatomist Sir Richard Owen discovered that "our arms and legs, our hands and feet, fit into a larger scheme" (30). He noticed a pattern in the bone structure of the human arm and leg: one big bone followed by two bones, a bunch of little bones, then digits. He focused the rest of his research on the similarities between skeletons of different organsism instead of how skeletons vary between different organisms (as many anatomists did at that time). He found "exceptional similarities" between animals that seemed to have nothing in common, like a whale and a frog. It appeared that all animals with limbs followed the one bone-two bones-lots of blobs-digits pattern. This discovery gave birth to an interesting question: How can modern-day animals be so different yet be so similar? What kind of environmental pressures could have caused a Common Ancestor with the one bone-two bones-blobs-digits pattern evolve into the animals that inhabit the Earth today? Use the Biological Theme of Evolution to support your answer.
Mikey Ling
(mikeyling@ymail.com)
This comment has been removed by the author.
ReplyDeleteModern animals are so similar yet different because they all stemmed from the same ancestors. This is very similar to the way that humans all look very different, even though over 99% of their genes are identical to each other. One reason that these organisms had to evolve in different ways is because of ecological niches. Only one type of organism can live in a community for a certain niche as resources are short and, "When competition between species with identical niches does not lead to local extinction of either species, it is generally because one species' niche becomes modified" (Campbell 1199). It is called resource partitioning when different organisms live in one spot by each using a different resource.
ReplyDeleteWell firstly, the one bone-two bones-blobs-digits pattern started because the animals needed more mobility and flexibility as they moved from water to land. This evolution occurred because the land required the ability to be able to bend ones appendages in very extraneous positions to cross the uneven grounds. Therefore, any animal that didn’t have a descending bone sizes from shoulder to wrist died from not being able to reach food sources and escape predators. Therefore the animals that have smaller bones on appendages survived and reproduced, making them a prominent creature on land.
Even though animals have greatly increased in size compared to the first land animals, they still remain to keep this bone structure. This is because the large bone located closer to the core of the body has more pressure put on it, therefore requiring it to be tough so the animals can cross over all types of environments. Actually the structure of the leg is copied in many crafts such as carpenters because, “The two bones of the lower leg, the large tibia and the smaller fibula, come together at the ankle joint to form a very stable structure” (http://www.eorthopod.com/content/foot-anatomy). This is important because as animals began to go deeper into land and away from water, they encountered more diverse environments which caused them to be sturdy (one main bone at the start) and nimble (hence the blobs-digits).
Jackie James
(jackie.james@comcast.net)