1) Homologous Trait
Humans and Bats
a)Humans and bats both share the same bones. They are both mammals and they both possess forelimbs which include the humerus, radius, ulna, carpals, metacarpals, and phalanges.
b) The homologous trait of these species is the forelimb. The forelimb of a human and a bat are structured similarly. Although they seem to look alike, they are used for different purposes. Humans use their forelimbs to reach for objects and to pick up objects. Whereas, bat's forelimbs have evolved into wings, allowing the bat to fly. These mammals with similar bone structures have adapted to survive in their own environments.
c) The common ancestor of humans and bats are a mammal that dates back to 80 million years ago. New York Times states, "This tiny shrew like creature was the common ancestor of humans and other living mammals as diverse as horses, bats, tigers, and whales."
2) Analogous Trait
Human Eyes and Squid Eyes
a) Humans belong to the vertebrate family and squid belong to the cephalopod family. They live in very different environments. Humans live on land and squids live in the sea.
b) The analogous trait that they share are their eyes. They appear to be similar in structure. They both contain an iris, a lens, a retina, and a cornea. Although the structure is the same, they had to adapt to their environment independently. For example, a human's pupil is round and changes diameter depending on the amount of light in the environment. Whereas, a squid's pupil is square and adjusts for the level of light by changing from a square to a narrow rectangle. (http://www.thecephalopodpage.org/cephschool/CephalopodVision.pdf) Although they work differently,the eyes were still developed for the vertebrates and cephalopods because they need them in order to survive. Humans and squids alike, use their eyes to hunt or run from prey. Since the squid victim to more prey than humans, they have developed better eyesight that does not contain any blind spots.
c) The last common ancestor for humans and squid is thought to be the acorn worm that has been around on Earth for 500 million years. The acorn worm is known to be the ancestor of humans, cephalopods, and all animals with backbones.
Good description of your organisms and good explanations as to their similarities and their differences.
ReplyDeleteWhile it helps to know who the common ancestor might have been, by itself, it doesn't confirm that these are homologous traits. In order to know that, you need to know if that common ancestor possessed the ancestral form of the trait in question and passed it down to the modern species. Since both humans and bats are mammals, we know that the ancestor was an archaic mammal who, by definition, would have possessed that ancestral limb form. This is what we need to know to be sure these traits are homologous.
Great choice of analogous traits! The eye has evolved independently several times over earth's history and is a great example of convergent evolution. Good description of the unique structure of each. It is the differences in structure that are important clues to the fact that these eyes evolved independently. It is difficult to posit an evolutionary path that would have led to both types of eyes, making two separate paths more likely. That by itself isn't enough to confirm that that are analogous. We still need phylogenetic information and you have taken the first step to providing that by identifying the possible common ancestor as an ancient worm. The question is... did that worm possess eyes that it passed on to the octopus and/or the human? The answer is no. ;-) Eyes developed further along both lines of descent.
Good images and, with points regarding ancestry noted, good post.
Hello Jasmine, great job on the work and information you provided on your blog post. It was very clear and very understandable with the pictures you selected. It is also very interesting that bats and humans share the same types of bones, i never knew that fact.
ReplyDeleteHey Jasmine, I also did Humans and Bats as well as Owls. As it turns out, humans and bats also share the same trait of fingers. although the structure is a bit different, they both have a common ancestor which possessed fingers.
ReplyDeleteNice job on your post