Looking at a bird flying around in the sky, it would not normally cross your mind that the wing of that bird has the same structure as a dogs front leg. Birds are very different from dogs just looking at them. Dogs cannot fly around in the sky and land on high trees. Dogs do not eat bugs or lay eggs, but the homologous structure of the two species are more alike than the average person might know. The bone structure in the leg and wing are very similar, they all have the same bones just in different lengths or located in a little different order. Birds use their wings for travel and being able to escape predators in the wild. Dogs use their arms walking, standing, and survival. Birds do not use their wings for the things dogs use their legs for, they use their claws for picking things up and holding things. Their wings are basically for flying and protection. Dogs use their legs for walking around, their mouth is used for most of the picking up. Birds would have problems with predators if they had to walk around on their claws all day because they are small and other predators are faster than them. Them being able to fly helps them survive, just like dogs are able to run to get away from other harmful animals. The Tetrapod is the common ancestor that these two species have in common. These are the four-limbed vertebrates and their ancestors. There are four groups that are under the Tetrapod category and those include; amphibians, reptiles, mammals, and birds.
The wings of birds and bats are an example of an analogous connection between species. Both the bird and the bat use their wings for flight but they did not come from the same ancestor. The bone structure of the bird wing and the bat wing are different and the length of the bones in the wings are different. The bird wings are connected to the crocodile and the bat is connected to the mouse, so both of these species had evolution in their limbs to help with flight. The main reason that these species' wings developed like this was because of the need for flight even though they are not related by a common ancestor. The common ancestor of these species I could not find but the evolution was not from a species with wings, it was from a species with four limbs. Both the bird and bat have similar wings aside from one being flaps of skin and the other being feathers, and the bone structure has some major differences.
Usually I caution against using domesticated animals in these comparisons as they are subject to artificial selection more than natural selection. The limbs are old enough, from an evolutionary perspective, to avoid this problem.
ReplyDeleteWe can get a little more specific than tetrapod for an ancestor. Mammals and birds both arose from ancient reptiles, who also possessed this ancestral limb structure. That is how we know these are homologs, resulting from common decent, not from arising independently.
Good discussion on the analogous traits. In this trait as well, you are comparing mammals and birds, to the ancestry is the same. The difference is that you are comparing wings instead of just general skeletal limb structure. You seemed to be coming around to that conclusion in your discussion. Just make sure you understand this issue of ancestry.
Good images.
Hello Erica,
ReplyDeleteI really enjoyed reading your blog post. I like the introduction and the flow. I did enjoy the examples you used and how it was different to other blogs. I would of never thought that a dog and a bird would have any similarities. Overall good job!