Tuesday, July 23, 2013

Things aren't always as they seem

Just apon first glance, it is easy to differentiate between a horse and a human with simple yet obvious anatomical differences. But would you ever think that humans and horses, as well as other mammals, all share similar anatomy? Darwin himself struggled to think that finger bones could be used for holding in a human and fins in a whale. Horses and humans are not too different as well. The horses hove has overtime developed with hard, protective coverings that aided in their locomotion with speed and stability. Of course, this limited horses to use their limbs for only those purposes. Humans, on the other hand, have retained the five digit (that is, fingers and toes) that enable them to manipulate objects.


source: google images.


Horses are members of the order, Perissodactyla, and humans belong to the order, Primates. Both orders are part of the subclass Eutheria, placental mammals, and also part of the smaller group Epitheria. So the last common ancestor of horses and humans is "eomaia scansoria".

source: google images


Some animals, such as birds and bats, can appear to be related because of similar characteristics they posses. However, these similarities do not mean that they are related or belong in the same group, it just means that both species were pressured into similar morphology for better survival. Another great example of this would be the camera eye in vertebrates (particularity fish) and the octopus.


Common octopus Cephalopod-vertebrate eye
source: mapoflife.org                         Source: mapoflife.org

Both the eyes of cephalopods and fish are hard and nearly circular with transparent crystalline proteins. Both have developed these eyes independently for speed, resolution, and sensitivity. In particular, cephalopods are fast moving predators that need precision eyes to aid in hunting their prey.


Sources:

http://www.biolbull.org/content/210/3/308.full
http://www.hwdsb.on.ca/hillpark/Departments/Science/Watts/SBI3U/Assigned_Work/Evolution/Homologous_and_Analogous_Vestigial_and_Competition.pdf
http://www.mapoflife.org/topics/topic_7_Camera-eyes-of-cephalopods/
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4 comments:

  1. L RodriguezJuly 23, 2013 at 10:07 PM

    Great discussion on the forelimb of the horse and humans. Your image was perfect for showing the relationship.

    No argument that these two organisms had a common ancestor and that it was a placental mammal. But did that ancestor possess this similar forelimb anatomy and pass it onto these two descendent species? That is what makes it a homolog.

    Good description on your analog and the similarity in structure. Good explanation on why it is analogous. Missing the ancestry section? Images on this section didn't come through either. Make sure you check your post after you publish to see if pictures post correctly so you can make adjustments as needed.

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  2. UnknownJuly 24, 2013 at 6:11 PM

    Wow! You really nailed this post! Very well written and you have great information. I thought it was so interesting how you chose the horse and human for homologous trait. I never would of thought of them being homologous with one another. Your information and explanation was super helpful though and very good! Nice job Daniella!

    -Danni Thompson

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  3. UnknownJuly 24, 2013 at 9:51 PM

    Daniella,

    I think your choice to compare a human hand to a horse was very intriguing. I never would have thought teh structure of our hands were homologous to a horse! Overall, great post and very interesting read. I also appreciate how you included sources.

    Anne Tereska

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  4. UnknownJuly 25, 2013 at 6:25 PM

    Daniella,
    I really enjoyed reading this post! It was very informative and I love your comparison, it was very different. I like all your pictures and think its great how many sources you have. I also love your comparison of the camera eye in vertebrates and the octopus, it was very interesting to read. Great job!

    Lissette Salas

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