Module 2: Reflection Prompt

My favorite prediction from Darwin's idea of Descent with Modification is that species are not independent but are connected by descent from common ancestors. This can be seen in something like homology where part of an organism has a similarity in its function or form to another species due to a shared ancestor. 


An example of this would be the human appendix. The human appendix is a vestigial structure meaning that it is in a decreased sized due to low usage in the human body today. The human appendix is homologous to the caecum in animals like a rat who need a large one to produce cellulase in order to digest the cellulose in the plant cell walls that they eat. However since the human diet has evolved to include a wide variety of foods beyond plant material the size of this has shrunk drastically and the caecum is now not as large of a section in the large intestine and includes the extra piece of appendix. The appendix is still functional in the human immune system but does not harm the human if it is removed.



This image shows how a human appendix and caecum (right) is all consistently about the same size. While a rat has an enlarged caecum in relation to the rest of its large intestine. The bottom picture is a drawn comparison of both side-by-side. 



Sources:

https://www.merriam-webster.com/dictionary/homology

https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(Boundless)/18%3A_Evolution_and_the_Origin_of_Species/18.5%3A_Evidence_of_Evolution/18.5H%3A_Vestigial_Structures

https://med.libretexts.org/Bookshelves/Veterinary_Medicine/Book%3A_Anatomy_and_Physiology_of_Animals_(Lawson)/11%3A_The_Gut_and_Digestion/11.13%3A_Functional_Caecum

https://www.genome.gov/11511308/2004-release-scientists-compare-rat-genome

https://www.pathwayz.org/Tree/Plain/LARGE+INTESTINE

http://scienceline.ucsb.edu/getkey.php?key=3246 


Photo Sources:

https://www.google.com/search?q=darwin&sxsrf=AOaemvJgb4icyN1Svw17Xb3gQBjdXHWelg:1631061566263&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjTvo3qke7yAhUEk2oFHcQ_AegQ_AUoAXoECAEQAw#imgrc=mbtZNOngTQdlaM 



Comments

  1. Bryce KidwellSeptember 9, 2021 at 10:21 PM

    Hi Kate, I think you picked a good prediction of Darwin's because I think homology and vestigial organs are all really interesting. It is really interesting how evolution can modify, adapt, or just decide not to use certain organs or body parts. I also think it was smart of you to use pictures when you were talking about the similarities between the caecum and the appendix to help show the similarities.

    ReplyDelete
  2. Hannah NineSeptember 10, 2021 at 9:17 PM

    Hi Kate! I enjoyed reading about the evidence you found for your favorite prediction of Darwin's idea. I did not previously know what the function of the appendix was and you did a really good job explaining it! Thanks for learning me something new!

    ReplyDelete

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