A) The two species for the homologous trait are modern man and chimpanzees. Both species are very similar in almost every aspect. Man and chimps have two arms two legs each with five digits. The skull and all the features like eyes, ears, mouth and nose are all arranged the same with similar proportions. Muscle groups and bones and all major organs are also arranged in a very similar fashion.
B) The homologous trait is hands with four digits and an opposing thumb. The hands of a man and a chimp are almost exactly the same structurally with four digits and an opposing thumb on each hand. Both species use hands to grab things and pick things up although humans are able to do much more delicate actions. Chimps seem to have much larger hands in proportion to their bodies with much longer fingers. Chimps not only use their hands to grab things but also to swing among the tree top branches. When it comes to the feet, the differences are much more noticeable between the two species. While human feet are made for standing and walking, chimp feet are built more like a second pair of hands that can also be used to swing and hang on to tree branches.
C) The common ancestor of man and chimps is still a missing link but was most likely an ancient ape like creature. It is most likely that this common ancestor did posses this homologous trait of hands with four digits and an opposing thumb because it was passed on to both chimps and men.
2) Analogous Traits
A) The two species for the analogous trait are dolphins and sharks. These two species look very similar and live in the same environment but are two completely different animals. They both have similarly shaped bodies with fins and tails to swim through the ocean, but dolphins have a skeletal structure made up of bones while sharks have only cartilage. Dolphins also have lungs and need to breathe air through a blow-hole, while sharks use gills to extract oxygen from the water. Also, dolphins are mammals while sharks are a type of fish called selachimorpha. Sharks have even been around for about 420 million years when dolphins have only been around for about 10 million years.
B) The analogous trait in dolphins and sharks is fins. They both have three fins and a tail (or fluke for dolphins and caudal fins for sharks) which helps propel them through the water. Yet, sharks use their tail in a side to side motion while dolphins move their tails up and down. In general it seems they use their fins in exactly the same way to propel themselves through the ocean waters, although they are completely different animals and species.
C) To find the common ancestor for sharks and dolphins we would probably have to go back to an ancient early reptile or amphibian that lived on land or even an earlier sea dwelling creature. It might be possible that the shark’s ancestors never left the ocean while the dolphin’s ancestors did move to land and then returned to the sea as a mammal. It would be hard to find the common ancestor due to the difference of 410 million years of the existence of sharks and dolphins. Yet, I would still guess that common ancestor did have fins, because these two species have such a similar analogous trait.
Great until the last sentence:
ReplyDelete"Yet, I would still guess that common ancestor did have fins, because these two species have such a similar analogous trait."
Why would the common ancestor necessarily have fins if we are comparing analogous traits?
In all likelihood, yes, the common ancestor (who was probably a cartilagenous fish) did have fins. But that isn't where the dolphin acquired its fins. They arose independently.
Otherwise, good post.
The examples that you used for part 1 (Homologous Traits) gives a clear picture of the differences and similarities between humans and chimps.
ReplyDeleteI also compared sharks with dolphins (Analogous Traits) and before I did my research I would have never imagined that Shark and Dolphins are completely different animals and species. It is interesting to see two animals who are so similar, yet they each have a different ancestor.
To Dr. Rodriguez
ReplyDeleteQuestion 2c asks – “All pairs of organisms share some common ancestor if you go back far enough in time. Did the common ancestor of these two species posses the analogous trait? Why or why not?”
I do not see where it is asked for me to decide where the dolphin got his fins exactly. I only answered the question, which I decided was yes, using the information that I included my blog.
You ask “Why would the common ancestor necessarily have fins if we are comparing analogous traits?”
The reason for my answer was the fact that sharks have been around for 420 million years and dolphins have only been around for 10 million years, the common ancestor may have had fins because I imagine sharks never left the ocean. I stated the 410 million year difference in age between sharks and dolphins in my blog along with the possibility of the shark’s ancestors never leaving the ocean. I also stated the possibility of dolphins evolving from land mammals, which would in turn allow them to evolve fins independently.
So if you agree that the common ancestor probably was a cartilaginous fish, I am not sure how the last sentence of my blog was incorrect. I used critical thinking, which you say you support, and the ideas stated in the body of my blog to come up with my final answer.
I know opinions do not belong in science, but I was asked my opinion in the question.
I hope this explains my answer better.