Week 3 - Analogy/ Homology Blog Post
1. Homologous traits
Humans are mammals who give birth and have larger brains
than other primates. A common pet, the gecko, is a reptile that lays eggs, is
cold blooded and walks on all fours. Many may find it hard to believe that we
share any common genetic history with the gecko, but we do nevertheless. The
bones in our ears are the same bones that make up reptilian jaws and our wrists
and ankles.
The bones that make up our inner ear are the stapes, incus
and malleus. The stapes is the only bone in a gecko’s ear while the incus is equal
to a gecko’s quadrate and the malleus is equal to a gecko’s articular. The quadrate
and articular are bones that help make up the jaw of a gecko. Our wrist and
ankles help us make full contact with the entire span of our hand and foot.
This function is similar in geckos. Humans obviously don’t crawl on all four limbs
but walk on two feet using our ankles and rotate our hands using our wrists. Geckos
walk on all four limbs and can place the entire span of their feet on the
ground.
Links: Reptilian Jaw and Mammal ear, Origins of Tetrapods
2. Analogous traits
The platypus and duck species are understandably mistaken as
being related to each other despite not having common genetic history. Both the
platypus and duck species have a duck bill and webbed feet. Both these traits
are due to their respective environmental stresses and not from genetic
history. Notably, the platypus is a mammal (even though it lays eggs) while the
duck is a bird, making these two species very different from each other.
The platypus breathes through its duck-bill while
the duck uses its bill to sift food from water. The shape of it helps both the
platypus dive for prey and helps ducks dive easily into the water. Webbed feet
allow animals to swim easier. The platypus’s front feet are fully webbed,
allowing them to swim easily and navigate through mud. Ducks use their webbed
feet similarly but mainly to swim efficiently. Having a duck bill helps both
animals dive easier and webbed feet help them swim.
If we look back as far as possible to find a similar
ancestor, it would be the reptile. Both animals share this ancestor even though
the reptile doesn’t have either of theses traits. Because of this reason, we
know that the platypus and duck do not share common genetic history.
Links: Platypus , Duck adaptations
Links: Platypus , Duck adaptations
Hello Julissa,
ReplyDeleteWell I definitely learned my fact for the day! That is quite intriguing to find out that we as humans share similarities to the geko, this really helps in visualizing how closely related species are intertwined with one another. I do wonder if through science though that they will be able to use this relation to improve certain health conditions related to the ear?
In your analogous comparison of the duck and the platypus , a lot of individuals do think the two are related but they really aren't although they have some similarities the use of these traits are quite different as you had described. I am curious to know though if some of the traits that these two animals possess can have a relation to certain dog breeds, for example a dachshund, redbone coonhound, German wiredhair pointer, and new newfoundland all have webbed feet these were to help in aiding these dogs in going after their prey, seeing that most of their prey would also have webbed feet and would live in water/ muddy areas.
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ReplyDeleteGood opening descriptions of your species pairings, for both your homologous and analogous sections.
ReplyDeleteInteresting trait choices, but frankly I would have stuck with the inner ear bones. The wrist traits seem to have similar functions, so they wouldn't be homologous traits.
Back to the inner ear bones.... This is really interesting and I appreciate the description of the different functions of these bones. Any idea why these bones evolved in different ways? An image of this would have been helpful.
"Tetrapod" must means any organism with four limbs. That's too broad and it doesn't give us the information we need to confirm homology. Humans are mammals, who arose from reptiles. Since geckos are also reptiles, we know that both geckos and humans must have both shared a common reptilian ancestor. Usually, from that point, we can look to the fossil record for evidence of what the ancestral trait looked like, but I doubt that those tiny inner ear ossicles fossilize well. Regardless, we know that these inner ear bones, in various forms, are standard issue (so to speak) for hearing animals. We may not know what the ancestral form is, but we can deduce that the ancestor did have them in some form, which is what we need to know to confirm homology.
Good description of your analogous trait, but it would have been best to focus on one. Traits can have different ancestry patterns, so you really do need to look at one trait at a time for this assignment. The bills are tough structures that are more likely to fossilize, so I will focus there.
Good explanation on ancestry. We also know quite a bit about duck and platypus evolution which allows us to confirm that from an alternative set of facts.
Good images.
Hi Julissa,
ReplyDeleteGreat content. It was very informative and rather entertaining. I loved ready about the platypus and the duck especially because I decided to talk about the same two animals. I was fascinated to know that both come from a reptile ancestry, although, they look nothing like one. And isn't it crazy that both have similar structural features that work similarly for both but don't relate to the same family line at all. I actually had a hard time describing and comparing the two due to the misconceptions there are about the platypus. I tried to talk about their behavioral similarities , but tried to compare their ability to lay eggs although the platypus comes from a tree line of animals that birth instead of lay eggs. I certainly had a hard time and eventually ran out of time and couldn't complete the last two tasks so it was nice to read about they ancestry on yours. Great job.