Homologus Traits
1a. An example of homology is the forelimb of tetrapods
(vertebrates with legs). Two different species that possess the homologus trait
would be the frog and the rabbit. The frog which I would never see the similarities
unless I have seen the picture (see below picture), their body stance and the
way they jump to get around.
A frog is an amphibian. It spends part of its life in water
and part on land. The front legs are shorter than its hind legs.
Rabbits are small, fluffy, animals with long ears, fluffy
tails, and strong, large hind legs that are designed for hopping from one place
to another.
1b. The homologus trait in both the frog and the rabbit is
the forelimb of tetrapods. The frog has the forelimb but his feet are webbed
which help him swim. The rabbit has little feet with four long toes that are
webbed to keep them from spreading apart for jumping purposes. The homologus
traits exhibit differences between these two species the frog uses his webbed
feet to be a better swimmer and the rabbit uses his webbed feet to be a better
jumper.
1c. Eusthenopteron is a prehistoric fish. It has close
relationships to tetrapods. The prehistoric fish had ample fins had a sequence
of bones, including elements that match to the limb bones of land vertebrates—the
humerus, radius and the ulna.
2a The platypus have a sharp stinger on their heels of
their rear feet and use them to sting toxic stings to their enemy. Platypus
hunt underwater, the way their bodies are designed they can stay submerged for
minutes at a time.
Ducks have wide webbed feet that help this species to be strong
swimmers. A duck's bill is wide and compressed to serve as a scooper for
gathering food.
2b. Ducks and platypuses both lay eggs, different
structures of eggs.
2c. Reptiles lay eggs too.
Good homologous comparison and I am glad you didn't pick the rear legs! Those are actually analogous in their leaping structure, developed through independent lines of evolution from organisms who didn't possess these unique structures. The forelimbs of the frog and the rabbit, on the other hand, have not changed too mucy from their ancestral origins but the changes that we do see are due to differences in function and the environment, as you explain. Good explanation on the issue of ancestry. I agree that early tetrapods are a good general ancestor of these two organisms.
ReplyDeleteThe section on analogy got a little robbed on content. Your explanations in the homology section were thorough but the analogy sections were minimal. What happened?
Good description on the two organisms.
Yes, the trait of egg laying evolved independently in these two species (you could have used the bill structure as well). What environmental pressure could have driven this adaptation?
With regard to ancestry, remember that analogous traits need to evolve independently from the common ancestor in at least one of these organisms, otherwise, they are homologous traits. So how does knowing that reptiles (some of them) were egg-laying as well? Wouldn't that suggest that these traits are homologous?
Birds arose from their reptilian ancestors, so they did inherit the egg-laying trait from that common ancestor. However, the platypus is a mammal. Mammals are usually placental animals and the ancestor of the platypus would have been as well, which means the trait of egg-laying would have been a new derived trait in the platypus (the question of "why" still exists). The fact that this trait arose independently in at least one of these organisms confirms that they are analogous, but that thought process needed to be explained here.
Hi Lynda, I thought your homologous example was very descriptive and informative. I just want to clarify, for the analogous part are you comparing the feet of the two animals or the beaks? Are platypus' and ducks related? Regardless, I still learned a lot, I didn't know platypus' had stingers on their feet, so interesting!!!
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