a) Human beings are bipedal mammals meaning they stand on two feet and have an erect posture. Humans are omnivores and are innately social creatures. These two traits are major contributors towards the versatility of human beings as a species. The ability to adapt to any environment and being able to alter their environment to cater to their needs is the reason why homo sapiens is the apex predator of the global food chain. Cats are carnivorous mammals that have been domesticated through years of selective breeding. Their bodies are adapted towards killing small prey, i.e rodents and serve a predatory niche in the wild (feral cats).
b) The human arm and a cat's legs are homologous. Humans use their limbs for a variety of activities, they're used for defense, nurturing, building, climbing and a lot of other things. The versatility of human limbs comes from the evolutionary advantage of opposable thumbs which opened a wide variety of opportunities for humans to take advantage of their environment. Cats on the other hand (no pun intended) have much more specified roles for their limbs. Movement is probably the biggest deciding factor regarding the differences of limb structure between humans and felines. Cats are incredibly nimble and flexible creatures. Despite having similar bone content (humures, ulna, are thicker), structurally they are different due to the fact that the anatomy of a cat's limbs are specialized. A cat's "arm" is essentially a spring loaded mechanism that can; withstand falls from certain heights, be used for pouncing on prey (birds and rodents), jumping etc. Thus
c) Through some research I discovered that the common ancestor of these two mammals is a particular placental mammal. I know this ancestor possessed these homologous traits because it is the only possible explanation as to how homology exists between these two very different species.
d)
2.
a) Butterflies are colorful flying insects, some species pollinate plants and some serve as carnivorous predators who feed on smaller insects They belong to the same group as moths from an evolutionary and taxonomical standpoint. Birds are considered to be the last living dinosaurs on earth as indicated by fossil records. Birds have reptilian evolutionary origins and a large majority have the ability to fly. They serve a variety of different roles amongst a myriad of niches. Some are predatory (birds of prey), some are nocturnal, some are herbivores, and some are carnivorous.
b) The wings of a bird capable of flight and a butterflies are quite similar in function. Despite not sharing a common ancestor, they both developed the ability to fly thanks to convergent evolution (living within the same environment). Flight is a major evolutionary advantage, the development of wings between these two species largely contributed to their survival. Most notably the bird, as previously stated, they are the remnants of dinosaurs and it is heavily theorized that dinosaurs capable of flight were the ones who managed to survive numerous mass extinction events.
c) In the butterflies' case, yes, their common ancestor possessed the ability to fly (caddis flies) and through changes in their environment the butterfly we know today was conceived through years of gradual evolution. It is largely speculated by the scientific community that the common ancestor of birds were theropods (think of raptors), who clearly lacked the ability to fly. This fact alone is proof that the traits of these two species are analogous. Birds developed wings through evolution as it was an imperative tool for their survival within their environments.
d)
My post involved the similarities between human and bat arms, much like your post involves the similarities between human and cat limbs. Comparing these two posts, plus another post by a classmate which involved human and mouse limbs, I've drawn the conclusion that humans, cats, mice, and bats all share a common ancestor as they all have similarly structured limbs.
ReplyDeleteVery good choice of homologous trait, and good opening description on your homologous species. Well done explaining the different functions/environments that produced the different structures in these traits through divergent evolution.
ReplyDeleteYou go astray a bit in the section on ancestry.
"I know this ancestor possessed these homologous traits because it is the only possible explanation as to how homology exists between these two very different species."
Circular logic. I know it must be homologous because that is the only way to explain homology. :-/ And there is another explanation... the similarities might be due to similar selection pressures... i.e., analogy. We need to demonstrate homology, not just circle around and assume that must be the answer.
What we do know is that since both humans and cats are mammals, that means their common ancestor was also an archaic mammal. From fossil evidence, we know that early mammals also possessed this primitive limb structure and passed it onto these two extant species, with changes happening as the result of divergent evolution. That is the ancestral information we need to know to confirm that these are homologous.
Good description on your analogous species pairing.
"Despite not sharing a common ancestor..."
As explained in the guidelines, all organisms possess a common ancestor if you go back far enough in time, and these species are no exception. Otherwise, you do a good job of explaining the similar selection pressures that produced these similar structures.
Well done on the issue of ancestry. You don't directly address the issue of the common ancestor, but you do explain that we know that at least one of these species evolved wings independently of that common ancestor. That is what we need to know to confirm analogy.
Good images.