Homology vs Analogy
1.
Homologous Traits
a.
Humans are bipedal mammals in the family
Hominidae with origins in Africa about 250,000 years ago.. Giraffes have long
necks, have distinct spotted markings and are the tallest mammals on Earth.
b.
Despite the size differences, both giraffes and
humans have seven neck bones. Giraffes use their necks to reach for leaves in
tall trees. Each neck bone is about 11 inches. Humans have a much smaller neck
bones. Humans do not use their neck for neck battles like giraffes do.
c.
The common ancestor of these two species is a
mammal from the dinosaur era. The skeleton of the prehistoric mammal was
reconstructed and was discovered that it had 7 neck bones in its vertebrae.
2.
Analogous Traits
a.
Ducks are birds who like and live in places like
ponds, streams and rivers. They also have webbed feet. Platypi are mammals who
live in streams and rivers. They both like water and have a bill.
b.
Platypi and ducks both have bills and webbed
feet. The webbed feet help both species swim around and increase their mobility
in the water. The bills are used to catch their common prey, fish.
c.
Platypi are from the mammal family, while ducks
are from the bird family. They do not have a common ancestor as the platypi evolved
after birds and mammals went their separate ways in evolution.
I thought it was very interesting that you compared a human being to a giraffe! I did not even know that humans and giraffe have seven neck bones. that is crazy how each neck bone in a giraffe is 11 inches long. Also I did not know that the webbed feet help ducks and platypus swim around and increase their mobility in the water. super good information!
ReplyDeleteOkay on your opening section, but this was your opportunity to more fully describe these organisms to offer a clearer picture to your readers about what might have driven the evolution of these traits. This applies to both the homologous and analogous sections.
ReplyDeleteOkay on your next section, but you only explain what humans DON'T do with their necks. Explain this from a positive position... what do humans do with their necks that make the compact structure advantageous?
Good discussion on ancestry.
For your description/discussion your analogous traits, you should have focused on one trait and expanded your discussion. Guidelines ask you to choose one and describe the similarities in structure and how that was related to similarities in their environments, which is what we need to know to confirm analogy.
"They do not have a common ancestor.."
Full stop. ALL organisms share a common ancestor (this is explained in the guidelines) so you cannot use this as a basis to confirm analogy. So how do we confirm analogy?
For this explanation, I am sticking with the bill, which we can track in the fossil record:
The platypus arose from mammals, who arose from reptiles. Birds also arose from reptiles, and and then ducks evolved bills after that.. So in and of itself, that is sufficient to confirm that the bill structure arose independently in at least one of these species. But we also know that the platypus developed it's trait after it split off from mammals, since mammals don't have bills by nature. That means this trait arose independently in the platypus relative to that common ancestor with birds. T That's what we need to know to confirm that these traits are, indeed, analogous.