Analogy/Homology


1.   
    a.  A cat and a whale appear very different on the outside. Cats have four legs and dislike water so they spend their time on land. Whales on the other hand are the opposite; they do not walk on four limbs like a cat. They spend their time swimming in the ocean, propelled by fins.

b.      The homologous trait that these two animals possess is actually the forelimb structure of their bones. There are actually many species that share some type of forelimb structure.  The cat uses its front legs to walk, run and climb. They use the power of the forelimbs for speed and power. The whale uses its fins for swimming. The trait exhibits differences in the two species because they are influenced by the environment they live in, water versus land. This is why the cat has limbs and the whale has fins.

c.       Given that both a cat and a whale are mammals; their common ancestor that possessed this trait and passed it down must be a mammal. A good example to support this is humans also share the same forelimb structure. We are also mammals which gives more support to this ancestral claim being a genetic trait.

d.       



2.   
    a.  Birds and butterflies both have wings that allow them to fly. Birds are warm-blooded vertebrates that can pretty much live in any habitat given the right conditions.  Butterflies are cold-blooded insects that live in warm, tropical climates.

b. The wings in both of these animals possess similarities in structure on the surface and function by allowing both of these organisms to fly. They both have adapted to life in the air by evolving wings.

c.  While the bird and the butterfly might share a common ancestor, in order for the trait to be analogous, it needs to have arose independently in one of the species.  They are not related through direct ancestry. There are many differences in these traits under the surface of appearance.  Insects have two sets of wings while birds only have one pair. Butterfly wings do not have bones in them which are what makes them so light, compared to a bird that does. In fact, the birds bone structure (forelimb) is homologous to humans.

d.




Comments

  1. Aunt Throw 101February 27, 2020 at 7:35 PM

    Hello,

    I really liked the comparison you did between a cat and a whale, it was very interesting and fun to read. It's hard to imagine the two sharing a common ancestor. Also, very informative. It was also very interesting to read the differences between the wings of birds and butterflies. You supplied a lot of great information and made it very easy to understand. Very well done.

    Thank you,
    Jodi

    ReplyDelete
  2. L RodriguezFebruary 28, 2020 at 11:04 AM

    Homology: Okay on opening section but there is a lot more information that could have been offered here to help your readers understand the different evolutionary pressures involved here.

    You do a good job of explaining the differences in function for the forelimbs of these two creatures but you don't connect that with differences in function. You've provided an image of the skeletal structure here. It would have been good to use that image to describe the differences in structure resulting from the differences in function.

    On the right track in your ancestry section, but needed one additional piece of information. All organisms share a common ancestor... that doesn't automatically mean their traits are all homologous. We need to know that that common ancestor possessed that trait and passed it onto these extant species, and we know that from fossil evidence (as well as phylogenetic evidence).

    Analogy: Okay on opening description, but again, more could have been offered here.

    Yes, wings help with flight, but why is flight an advantageous form of locomotion? What evolutionary pressure drove the development of flight in these two species? Perhaps avoidance of predation?

    You started off correctly in your ancestry section, but here...

    "They are not related through direct ancestry. "

    You wander off a bit into trouble. *Traits* may not be related through direct ancestry, but *species* are. This needed to be distinguished. I don't disagree with the rest of your statement, but how does this confirm analogy beyond superficial observations? How do we provide evidence that these traits are indeed analogous?

    It is difficult to guess at what the common ancestor of the bird and butterfly looked like some 100's of millions of years ago... it may have possessed wings or it may not have, but fortunately, we don't need to know that to confirm that these traits are analogous. While it is possible that the butterfly inherited its wings from that common ancestor, what about the bird? We know quite a bit about bird and bird-wing evolution. Birds evolved wings as they split from reptiles, and this occurred long, long after the split with that common ancestor with the butterfly. This means bird wing evolution occurred independently from that common ancestor with the butterfly. That is sufficient to confirm that these are not the product of common descent and are indeed analogous.

    Good images.

    ReplyDelete
    Replies
    1. L RodriguezFebruary 28, 2020 at 11:06 AM

      First sentence in the second paragraph should read:

      "You do a good job of explaining the differences in function for the forelimbs of these two creatures but you don't connect that with differences in structure. "

      Delete
    2. darrenlafFebruary 28, 2020 at 9:08 PM

      Hi Am-

      Good choice on the whale and the cat. I've actually seen a couple of posts that used whales with other animals and it's amazing to see how many seemingly completely different animals share homologous traits. It made me think for a second that all must be that completely different but then I saw more similar animals, like frogs and lizards, that are more associated with relating to each other that also share these types of traits.

      Delete

Post a Comment

Popular posts from this blog

Piltdown Hoax

In 1912, an amateur archaeologist by the name of Charles Dawson claimed to have found an ancient piece of a human skull digging in a gravel pit in the small town of Piltdown. He started working with Arthur Smith Woodward, England's leading geologist of the Natural History Museum. Up to this point scientists had found remains of primitive humans in France, Germany and Asia, but none in England. Charles Dawson dug up a jawbone thought to have been part of the same skull, it was a major surprise because it looked more like an ape, but the teeth were worn flat much like a human. With this discovery, they thought they had found a common ancestor of a human and an ape. In December of 1912 at a meeting for the Royal Geological Society, scientists could now see that England had found fossil remains and their ancestors could actually be the oldest of them all. They called the discovery "Piltdown Man." After finding  more fossil remains, it had silenced those who were critics. Howe...
Read more

Historical Influences on Darwin

I believe Thomas Malthus had the most influence over Charles Darwin’s development of his theory of Natural Selection. According to Brittanica.com he actually anonymously published, An Essay on the Principle of Population which many took notice to. “He pointed out that in nature, there is a tendency for animal populations to increase in size, but the amount of resources remains relatively the same. Therefore population size is held in check by resource availability” (Jurmain et al., 2014, p. 32). Based on the main arguments held in Darwin’s theory, it seems Thomas Malthus touched on a major one; that resources are limited. No matter what has happened in the many generations that Earth and the population have changed, there has always been a struggle for resources. The saying my mom used to always tell me is that there will always be someone with more than you and someone with much less whenever I happened to seem ungrateful for something. She is not wrong, it is a harsh reality that so...
Read more