Analogy and Homology Blog Post
Homologous Traits:
Analogous Traits:
In nature, there are animals that possess similarities in the structure of their appendages but differences in how they use those appendages. Homologous traits show a common genetic relationship between two animals from their ancestry.
Dolphins are aquatic mammals that are social, possess rubbery skin, and glide through water while being propelled by their large fins. Humans are terrestrial mammals that are also very social, can swim, have a lot of hair for protection against the sun, and enjoy a nice cup of coffee on a cold winter day. The animals I have chose for this blog post are the common, well known, Homosapien and dolphins. You may be wondering, “How could a dolphin and a human have similarities?” Well, both dolphins and humans have an appendage that they use for every day functions that are similar in structure: the arm of a human and the flipper of a dolphin.
The homologous trait shared between dolphins and humans are their arms/flippers. The upper extremity of the human arm consists of 64 different bones while on a dolphin their flipper consists of roughly 34 bones. The similarities are in what bones are inside their flippers. Dolphins have an Ulna, a radius, a humerus, carpals and phalanges just like humans do. These Homologous traits are different because they are formed and fused differently than a human arm. Dolphins have a radius and an ulna that is super close together and tightly packed while humans have a radius and ulna that are slightly gapped. The flipper of a dolphin is also much larger and has much bigger bones than the tiny carpals and metacarpals of a human being, which is why they have less bones. They use these structures as their main source of mobility because they don’t have legs like humans do. They tread water with the size of their large flippers and use their appendages completely different than humans do. Humans can also tread water, but aren’t as well adapted as dolphins due to dolphins having flippers regardless of their similar bone structure. Having these homologous traits shows similarities between the two species because both species have interactions with water and both use their extremities for other purposes instead of strictly using them for mobility. The link between the two is their ability to tread water and use their flippers to function.
The common ancestor of humans and dolphins would be any kind of Artiodactyla like Hippopotamus and Whales. They are common ancestors because hippopotamus possess multiple bones in the tip of their feet and whales possess multiple bones or similar bone structure in their flippers. Dolphins and humans have not had a true common ancestor in 95 million years, but they still share similarities because they most likely originated for one common ancestor.
Analogous traits are traits that are not passed on by an ancestor, but instead are evolved in a species due to natural or environmental pressures. The animals I chose for the Analogous traits are a rat and a common household cat. A rat is a small rodent that has four paws, a long tail, and really big ears. A common household cat is small feline that has sharp teeth and claws but doesn’t need to hunt for food, though they can hunt for mice around the house.
The analogous trait of both of these animals are their tails. A cat has a long tail to help them balance on all types of things like furniture, fences, and even the ceiling fan somehow. Rats on the other hand have a tail that can help them with balance, fighting other rats, or as a distraction. They are both made up of many tiny bones and muscles that can help them articulate their movements. These two species both have long tails, in proportion to their bodies, because they both need to be able to balance themselves well. They are both similar because of the environmental pressure they are under. Cats and rats both like to hide in places where balance is key, especially when a rat is in the sewer, they need their tail in order to run along long beams without falling. A cat's tail and a rats tail acts like a counterbalance for their offset footing.
I feel like the common ancestor of these two could have possessed this common trait because it was most likely some sort of reptile with a tail. Balance is important in the animal kingdom because those who don’t have balance can’t hunt properly. I know these traits are analogous and not genetically related from common descent because a rat is classified as a rodent and a house cat is a feline. They are two different genetic makeups that both evolved to adapt to environmental pressures like reaching high places and maintaining balance.
Homology:
ReplyDeleteGreat opening description.
For the most part, good discussion on your homology, but with a curious omission. You describe structural differences thoroughly, but when it comes comes to function, you get stuck in an aquatic environment, explaining how the dolphin fin is adapted to movement in water, but then you don't explain what human limbs actually are adapted to, such as manipulation of our environment. You only told half the story here.
The hippopotomous and whale are modern species and could not be ancestors of other modern species. But do we need to be this specific to answer this question on ancestry? Both humans and dolphins are mammals, so we know that the common ancestor would be an archaic mammal. We also know from the fossil record that early mammals possessed that generalized mammalian limb structure and passed that onto these two descendant species, with changes concurring over time due to differences in the environment (aquatic vs. terrestrial). That is what we need to know to confirm common genetic origin and confirm homology.
Analogy:
Good opening description.
The tail trait is actually homologous, not analogous. We know this because they are both mammals, and the general trait for all mammals (humans/apes have derived different forms) is to have a tail. Both the cat and the rat arose from an archaic mammals, which we know from the fossil record possessed a tail. That means that these traits CANNOT be analogous. They were inherited via common descent.
Your description of these traits are good but you are misreading the ancestry issue here.
"I feel like the common ancestor of these two could have possessed this common trait because it was most likely some sort of reptile with a tail. "
An archaic mammal, actually, but shouldn't this have been an indicator to you that this is NOT an analogous trait? To be analogous, the trait needed to arise independently in at least one of the species. Both inherited from the common ancestor, so this doesn't support your claim of analogy.
Check some other student posts for examples of analogies and email me with any questions.
Good images.
Homologous Traits:
ReplyDeleteI found it very interesting how you compared the human structure with dolphins. You really went in depth with the number of bones inside the body parts and the same types that we share with the dolphin. You compared the differences of how we operate and use our body parts but you also showed the relationship between the two. You explained how the dolphin has less bones inside but it has many more uses and it stronger than our human arms. The stronger bones allow for better mobility in the water as the dolphins do not need the use of legs. I did not know of the shared common ancestor between the two so it was news to me reading your post.
Analogous Traits:
The cat and rat comparison of the analogous traits were interesting. They both share the trait of having a tail but they both use it for separate reasons which was intriguing. Although both of the species use their tail for balance purposes, they were both put under different environmental pressures which caused them to evolve differently. Introducing the trait of balance for hunting being important in the animal kingdom was substantial because many of the previous ancestors would have implemented these techniques in the past. Overall, good blog post.
I love how many people are doing their comparisons on humans compared to other species. In my opinion I think dolphins in a way are almost as smart as humans. I think it is interesting on how you explained about the dolphins bone functions compared of that of a human bone structure. It is crazy to think that evolution is true but its obvious that it is evident in our environment.
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