Examples of Homologous and Analogous Traits
1.
A. Starting with a leg of a dog and pectoral fins of a dolphin, both
are used very similarly. They both propel the animals forward, and are
both constructed of bones. A dog’s leg provides it the ability to both
jump and move them forward. Much like the human skeletal structure,
dogs also have the large thigh bone femur which links to the fibula and
tibia. A dolphin on the other hand uses it’s tail and fin to swim while
providing directional control. The dolphins pectoral fins, like a
dog’s leg are connected by a series of bones.
B.
However, the traits both animals possess are distinctly different.
The dog can use this limb to jump, leap, run, and walk while the
dolphin is limited to using the fin to guide itself and swim by pushing
water back. Clearly, the traits must be different due to their
environments. The swimming back and forth motion a dolphin is limited
to would be nearly useless for the dog, who lives on land. Meanwhile,
the ability to push off the ground with little surface area would prove
meaningless for a dolphin, which requires fins, that can push back large
portions of water which pushes them forward.
C.
Possible ancestors to both the dolphin and a dog may have been mammals
that lived on land with a branch of the species hunting for food in
water while another needed faster legs with jumping capability. The
need to move quickly in order to feed is a clear similarity the
ancestor, dog, and dolphin all share.
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2.
A + B. Dragonflies and vultures both have sets of wings. However,
dragonflies and vultures have wing structures completely independent
from each other and operate differently. The dragonfly have incredibly
powerful wings allowing them to reach speeds up to a record 60 miles per
hour. Meanwhile, the vulture has large boned wings which are used to
help control it’s altitude. Dragonfly use their wings are their only
means of transportation because despite having 6 legs, they can only use
their legs to land and crawl at very slow speed. The vulture uses it’s
wings to fly high and scavenge for food, fly in circles around a
potential meal, and stabilize itself when landing. The wings of both
the dragonfly and vulture are both used to fly, showing that the general
purpose of the trait was similar. The two sets of wings were developed
over long periods of time to help fulfill their needs.
C.
Although all life share 1 common ancestor, the trait seems to have
been adapted due to environmental stress. The dragonfly for example,
does have 6 legs, it is likely the dragonfly used the legs as primary
means of travel before it had wings.
I had no idea that dragonflies had six legs, interesting! I agree with you on the idea that dragonflies and vultures inherited the trait due to environmental stress. It seems to me as time went on and the species began to separate into two distinct species natural selection took place but because of their shared ancestor the trait just continued to evolve in both species.
ReplyDeleteGreat discussion and explanation on your homologous traits. Good outline on the ancestry of both and how this support the classification of the forelimbs as homologous traits.
ReplyDeleteVery good background description of your analogous traits and their organisms. With regard to ancestry, yes, they do have a common ancestor if you go back far enough but do you need to even consider this to know that they are analogs? When did the wings in birds evolved? Did they arise independently from their ancestry with insects (some hundreds of millions of years ago)? Answering these questions will give you a clearer answer that supports these traits as analogous.
Other than this point, good post.
David,
ReplyDeleteThis was very insightful. I was surprised to find that dogs and dolphins had anything in common. It is interesting to see what certain bones evolve into depending on their environment. Im curious to know what common ancestor the dragonfly and vultures share.
-Vionne Pilas
Thank you all for the feedback. I now realize that my analogous portion of my research was a little lacking, resulting in many questions. The ancestors to a Dragonfly can possibly be some sort of mollusk or jellyfish, which both propel themselves through water by squeezing water through the body, the same way Dragonfly larva do while in the early stages of it's life. The vulture on the other hand had hawk and eagle ancestry using their strong eyesight to catch prey. It seems possible that in order to increase it's speed that both separate species grew wings.
DeleteHello David, the examples you gave very very interesting. just think it is crazy how species are able to change due to the environment. I like the example of the dog and the dolphin, and how they use their legs in a similar way. Dogs use them to move forward and dolphins use their fins to move forward as well. In my post i did the wrong species because i was not understanding, but your post and another persons post was of great help to get a better view. I was comparing the wrong animals! great post!
DeleteHello David,
ReplyDeleteI find your post interesting, as it easy to forget that fairly large vulture and a tiny insect have something in common. I had dragonflies in my backyard often and noticed they had two sets of wings, not just one. I looked up why that is and the website telegraph.uk.com states that they are used to fly faster and that each wing can be operated independently. Thank you for bringing up a creature that I would have never looked into.The website states there is evidence to insects 300 million years ago apparent in the dragonfly. Who knew? Interesting post and a great post to trigger interest to look up this insect. Also, I love the images of the dog and the dolphin.
Great post.
Best,
Andrea
Hello David!
ReplyDeleteI find it really amazing that dragonflies and vultures were able to develop wings from environmental stress. I found the same thing to be true about butterflies as well. What interests me the most about your post is how the wings of each species are used. From your posts I was able to clearly understand the need for these species to evolve. In order for a vulture to fly at a high altitude it would need strong and heavy wings. While the dragonfly would instead need wings that are quicker and more lightweight. The second thing that interested me is how you were able to find your homologous trait between a dog and a dolphin. Although both are intelligent species it didn't occur to me that they shared a similar trait.
Wonderful Post! I also enjoyed the picture of the dolphin.
-Marina