HOMOLOGOUS
1) The two different species I chose as having homologous traits are human beings and birds.
2) The homologous trait they share is the forelimb. Though humans are covered in skin and birds in feathers, their forelimbs have the same bone structure. These would include the humerus, ulna, radius, carpals, metacarpals, and phalanges. However, modifications have been made to each species to suit their specific functions. Humans y=use their forearms to reach and pick up objects, while birds forelimbs have evolved to help them fly. The reason they differ is humans lived on land and birds lived in trees which gave them the need to fly.
3) The common ancestor of the two species is thought to be Archaeothyris.
file:///Users/Guest/Documents/human%20and%20bird%20structure.jpg
ANALOGOUS
1) The two different species I chose with analogous traits are bats and birds.
2) The trait they share is their wings. Even though they both have wings for flying, their wings have evolved over time independent of each other, with no common ancestor.
3) Going back far enough in time, the common ancestor birds and bats shared were terrestrial quadrupeds. However, the bats flight happens because of a structure that consists of a membrane stretched across four extremely elongated fingers, while a bird's structure is made of feathers, which are strongly attached to the forearm (the ulna) and the highly fused bones of the wrist and hand, with only tiny remnants of two fingers remaining, each anchoring a single feather.
Hi,
ReplyDeleteThe comparison between the human and the bird is a good example to show the homologous trait between the two. They do share a common trait such as their bone structure in the arm and wing. Both have the same bones but in varying length and width but are still very common and considered homologous. With this it does show the differences such as the human having skin and hair while the bird wing has feathers. Each serving a specific purpose and function because one needs to fly while another lives on the ground and the use is like you say for picking up objects and leveraging itself of the environment. I think the common ancestor between the two is a good example because both could have branched from this one reptile.
The analogous traits between the bat and bird is a good example to show the independent evolution of a similar trait of flight. Both have wings but the differences in wings is an analogous trait. Bats have skin stretched between the fingers while the bird has feathers and another distinguishing factor is that a bird lays eggs while interestingly the bat is a mammal.
Good choice of homologous trait, and you have a clear description of how the function differs, but how is that reflected in the structure? How do the bones differ, not in the bones that are there but in the shape of the bones? Your images didn't come through, and that might have helped with your explanation. Check the "help" page on the course blog to get some guidance on posted images to your blog.
ReplyDeleteThe bat/bird comparison is the same one presented in the guidelines, which said that this example couldn't be used in your post. Partial credit.