1. Two different species I found that possess the homologus trait are the frog and the lizard. A frog is a tailless amphibian with a squat body, and the lizard is a reptile with a long body and tail. According to the website dictionary.com in the article entitled Homology in the Animal Kingdom, last accessed on February 2015, it states, "Though they clearly look different, they both share the same common ancestor and a common set of bones (the radius, ulna, humerus)".
b. The trait these two animals have in common are their forelimbs. The forelimbs of a frog and a lizard look very different because they have evolved differently to assist in the specific lifestyles of each animal. The forelimbs of a frog consist of a humerus, radioulna, carpals, metacarpals, and phalanges; where a lizards forelimbs consist of a humerus, ulna, radius, radiale, centrales, metacarpals and distalia. The frog uses its hind forelimbs for swimming and leaping, and its smaller, upper limbs for steering when it is swimming and for absorption of shock when landing after a jump. The lizard uses its forelimbs for running, balancing, gripping and for holding on to things. The traits are different because it is necessary in order for the animal to survive in its environment. The frog is a water animal, where the lizard lives mainly on land.
(See photo above) Though Eusthenopteron was a fish, it sometimes came up on land to search for food when none was found on the ocean floor.
ANALOGS
1. Two species that I found to possess the analogous trait are the Platypus and Duck. Contrary to what some people may think, they are not, both birds. One is a bird, and the other is a mammal. Both however, do lay eggs.
b. As previously stated, they are both egg laying creatures that have webbed feet, and a soft, smooth rubbery snout. A platypus lays one to two eggs at a time and keeps them warm by holding them between her body and tail. The eggs hatch in about ten days. On the other hand, a duck can lay between 9 to 12 eggs at a time (depending on the type of duck), which it buries in a nest till they are ready to hatch about 28 days later.
c. I do believe the common ancestor in both could have shared this trait because otherwise, I don't think a platypus would be able to lay eggs if it is a mammal, I don't see the point to it. Why not instead just give birth to its babies like other mammals? I think we know it is an analogous trait because its clear that they are not alike, aside from the snout they both possess and the fact that they both lay eggs, they look and are nothing alike. I think the platypus looks more like a mixture of a seal and a beaver.
I think you had a very good, informative post. You explained each part well and included some good details. I liked reading about the frog and lizard because before reading I'd think they would have a common ancestor since they look so similar. But now I know they don't. And I knew virtually nothing about platypus's so I enjoyed learning about them, their breeding habits and what analogous traits they have. Overall, good post!
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ReplyDeleteRebecca,
ReplyDeleteI really enjoyed your post, it was laid out very nicely and contained some good information. It's weird to think that both animals are so different yet they both lay eggs in a similar fashion. It's awesome to think about how nature works.
Good and thorough description of your homologous pairings. I'm not familiar with the "distalia" structure in lizards. Can you describe what that structure is?
ReplyDeleteGood research on the lobed-finned ancestor, but we don't need to go back that far to find a common ancestor. Frogs are amphibians and reptiles arose from archaic amphibians, so the common ancestor was an early amphibian. We know that the generalized amphibian limb structure includes those skeletal structures. That is all we need to know to confirm homologous status.
Good discussion of your analogous traits.
With regard to your ancestry discussion:
"I do believe the common ancestor in both could have shared this trait because otherwise, I don't think a platypus would be able to lay eggs if it is a mammal, I don't see the point to it."
Your ability to see the "point" is not evidence that the common ancestor possessed the trait! Besides, remember that for analogous traits, we need to demonstrate that the trait in question did NOT arise from common descent. So if the common ancestor possessed the trait, how does that help support the argument that the egg laying trait is analogous?
Interestingly enough, you actually state the fact that supports the case. Mammals in general don't lay eggs. It is not the generalized trait of mammals. It is a uniquely derived trait of the platypus, a trait that evolved in the platypus line alone. That means it evolved independently from egg laying in birds (and their reptilian ancestor). That makes this an analogous trait.
Good images.