Analogy/Homology of Different Species
1. a) Human hands and the hands of a chimpanzee are homologous. This means that humans and chimpanzee's shared a common ancestor about seven million years ago. As to some background, Chimpanzee's are a species of ape and bonobo closely related to humans. Chimps historically inhabit tropical forests and savannas. Humans were said to have much of their evolution occur on the continent of Africa and some of the earliest fossils come from 6 million years ago of which come entirely from Africa. Some additional descriptional background information of the Chimpanzee: they are covered in a coat of hair (usually brown), The diet is also primarily vegetarian, this diet consists of berries, seeds, and insects. Additional Human background information: homo sapiens emerged around 300 to 200 thousand years ago.
b) The major function of the hand in all vertebrates except humans is locomotion. Chimpanzees and the other vertebrates use their hands to help do things suck as balance themselves, pick up objects, and to move up trees. Humans however, although the uses listed also apply, also use their hands to communicate using hand signals and to draw or study with. These are distinctly difference usages for these two homologous traits. Human hands are also free rather as humans are upright they are not needed for support. These homologous traits are different between the two species because of the environmental difference and needs that were needed. Humans started using more tools and started walking upright, and this may account for some of the structure differences seen in these two homologus species. We humans have relativley long thumbs which make it easy for us to touch our thumb to any finger, this is a contrasting difference to the chimpanzee hand. This is related to the function of the two hands. The functions were stated previously as humans use more tools and signaling/hand gestures and chimpanzees have shorter thumbs perfect for swinging.
c) Chimpanzees are genetically the closest to humans since we share about 98.6% of our DNA with them. With that said the last common ancestor is generally regarded to the an extinct hominine Sahelanthropus tchandensis (I think this may be too specific but I was hesitant to leave it too general). The fossils of this species has been analysed and it was confirmed to be a direct ancestor of Homo and Pan because of the anatomical similarities seem to hominins. Since there seems to be similarities within the anatomical features and there is also a direct correspondence to Homo and Pan it is likely the homologous trait of hands were passed down. In clarification, similar anatomical features do not directly correlate to homology, but as states, it is the fossil data and the direct correspondence to Homo and Pan which supports my claim of homology.
d)
2. a) The flippers of a dolphin and the fins of a shark are two analogous traits possessed by these two difference species. Both of these aquatic species have evolved to swim after their food with their streamline bodies and similar structures. Sharks have pectoral fins and dorsal fins that allow them to glide through the water. The dolphin had flippers and a torpedo-shaped body which is contrasting from the sharks body. The dolphin flipper is also made of bones while the shark pectoral fins are made of cartilage. Some additional descriptions of the shark: they do not nurse their young, they do not have hair and they use gills to get oxygen from the water. Dolphins do nurse their young and also do have hair. They cannot breathe underwater as they do not have gills. Rather, Dolphins have blowholes so they must swim to the surface every so often.
b) The flippers of a dolphin and the fins of a shark are similar in structure because it has similar shape and it allows them to be efficient and move around when swimming through water. Both are aquatic creatures so it makes sense as to why the flipper and fin structures have much similarities. The aquatic nature of the environment made it so that a well developed/shaped fin or flipper would be advantages to the shark or dolphin. This was the driving factor is having this convergent evolution since the two species didn't come from the same ancestor.
c) Sharks and Dolphins don't actually share a common ancestor or at least it isn't known. We know that "sharks were swimming through oceans long before dolphins had descended from land dwelling mammals" (Berkeley). This is how we know that the traits are not genetically linked from common descendants and therefore are analogous.
d)
(Berkeley)
References:
https://evolution.berkeley.edu/evolibrary/article/0_0_0/similarity_hs_09
https://evolution.berkeley.edu/evolibrary/article/0_0_0/similarity_hs_11
https://www.khanacademy.org/science/in-in-class-10-biology/in-in-heredity-and-evolution/in-in-evolution-classification/v/homologous-analogous-structures-heredity-evolution-biology-khan-academy
https://evolution.berkeley.edu/evolibrary/article/analogy_04
b) The major function of the hand in all vertebrates except humans is locomotion. Chimpanzees and the other vertebrates use their hands to help do things suck as balance themselves, pick up objects, and to move up trees. Humans however, although the uses listed also apply, also use their hands to communicate using hand signals and to draw or study with. These are distinctly difference usages for these two homologous traits. Human hands are also free rather as humans are upright they are not needed for support. These homologous traits are different between the two species because of the environmental difference and needs that were needed. Humans started using more tools and started walking upright, and this may account for some of the structure differences seen in these two homologus species. We humans have relativley long thumbs which make it easy for us to touch our thumb to any finger, this is a contrasting difference to the chimpanzee hand. This is related to the function of the two hands. The functions were stated previously as humans use more tools and signaling/hand gestures and chimpanzees have shorter thumbs perfect for swinging.
c) Chimpanzees are genetically the closest to humans since we share about 98.6% of our DNA with them. With that said the last common ancestor is generally regarded to the an extinct hominine Sahelanthropus tchandensis (I think this may be too specific but I was hesitant to leave it too general). The fossils of this species has been analysed and it was confirmed to be a direct ancestor of Homo and Pan because of the anatomical similarities seem to hominins. Since there seems to be similarities within the anatomical features and there is also a direct correspondence to Homo and Pan it is likely the homologous trait of hands were passed down. In clarification, similar anatomical features do not directly correlate to homology, but as states, it is the fossil data and the direct correspondence to Homo and Pan which supports my claim of homology.
d)
2. a) The flippers of a dolphin and the fins of a shark are two analogous traits possessed by these two difference species. Both of these aquatic species have evolved to swim after their food with their streamline bodies and similar structures. Sharks have pectoral fins and dorsal fins that allow them to glide through the water. The dolphin had flippers and a torpedo-shaped body which is contrasting from the sharks body. The dolphin flipper is also made of bones while the shark pectoral fins are made of cartilage. Some additional descriptions of the shark: they do not nurse their young, they do not have hair and they use gills to get oxygen from the water. Dolphins do nurse their young and also do have hair. They cannot breathe underwater as they do not have gills. Rather, Dolphins have blowholes so they must swim to the surface every so often.
b) The flippers of a dolphin and the fins of a shark are similar in structure because it has similar shape and it allows them to be efficient and move around when swimming through water. Both are aquatic creatures so it makes sense as to why the flipper and fin structures have much similarities. The aquatic nature of the environment made it so that a well developed/shaped fin or flipper would be advantages to the shark or dolphin. This was the driving factor is having this convergent evolution since the two species didn't come from the same ancestor.
c) Sharks and Dolphins don't actually share a common ancestor or at least it isn't known. We know that "sharks were swimming through oceans long before dolphins had descended from land dwelling mammals" (Berkeley). This is how we know that the traits are not genetically linked from common descendants and therefore are analogous.
d)
(Berkeley)References:
https://evolution.berkeley.edu/evolibrary/article/0_0_0/similarity_hs_09
https://evolution.berkeley.edu/evolibrary/article/0_0_0/similarity_hs_11
https://www.khanacademy.org/science/in-in-class-10-biology/in-in-heredity-and-evolution/in-in-evolution-classification/v/homologous-analogous-structures-heredity-evolution-biology-khan-academy
https://evolution.berkeley.edu/evolibrary/article/analogy_04
I think you did an excellent job detailing the common ancestry between humans and chimps. You began with some good points on the evolution of humans and chimps from a common ancestor and then focus on the homologous trait of the hand and how there are distinct differences in how humans utilize their hands as opposed to other vertebrates. The example of explaining how humans became upright does a good job of showing divergent evolution in the use of hands between humans and chimps. I can recall hearing and reading in many different forums about the similarities between humans and chimps , and your reference to 98.6% of DNA drives that point home.
ReplyDeleteHomology:
ReplyDelete"Human hands and the hands of a chimpanzee are homologous. This means that humans and chimpanzee's shared a common ancestor about seven million years ago."
You have the causal relationship backwards. The hands of humans and apes are homologous *because* they inherited it from a common ancestor some 7 million years ago.
Good opening description.
You discuss the differences in function very clearly but you don't offer a lot in terms of how those differences in function translate to differences in structure, which is the actual trait you need to be comparing here. You briefly mention the length of the human thumb but you don't describe the chimpanzee hand at all. How do these hand structures differ? And how do you explain these differences in structure in terms of their differences in function in their given environment?
You first sentence was closer to what you needed in terms of ancestry to confirm homology. Both humans and chimpanzees are primates, so we know that the common ancestor would be an archaic primate. We also know from the fossil record that early primates possessed that generalized primate hand structure and passed that onto these two descendant species, with changes concurring over time due to differences in the environment (manipulative vs. arboreal). That is what we need to know to confirm common genetic origin and confirm homology.
Analogy: Good description and good discussion of the traits you are comparing.
"Sharks and Dolphins don't actually share a common ancestor or at least it isn't known."
We may not know the exact common ancestor, but we have general idea and can use that information to confirm that these traits are analogous. Assuming that there is no common ancestor is not sufficient to assume analogy, because science doesn't permit unsupported assumptions. So how do we confirm analogy?
Dolphins are mammals, who arose from reptiles, who arose from amphibians, who arose from archaic fish. Sharks are fish, so that means both share a common fishy ancestor... but since fish possess the fins in question, does that mean these traits ARE the product of a common genetic origin? No, because we know that dolphin fins evolved after their mammalian land ancestors moved back into the aquatic environment (and we have the fossil evidence to support this). Yes, the shark inherited its fins from that common ancestor, but as long as the trait arose independently in at least one of this paired species, that is sufficient to confirm that the traits are analogous, not genetically related.
Good images.