An example of a homologous animals would be crabs and spiders. Both of these animals came from the Arthropoda. This would in turn split off and evolve into Crustaceas, i.e crabs and lobsters, and Arachnida, i.e spiders and scorpions. While crabs are sea creatures that have lived underwater for hundreds of millions of years they have, like the spider, developed a hard exoskeleton made of chiton, they molt, and have jointed legs. Crabs are creatures that troll seabeds, they are omnivores that typically eat algae, and are referred to in some circles as ‘sea bugs’. Crabs are found all over the ocean, rivers, and even on land (though still nearby water). Spiders on the other hand are land based creatures that form webs as a way to capture their prey, they have 8 legs and tend to be in small, isolated spaces. Spiders can also be found around the globe and it’s thought the widespread of spiders have been helped by the international shipment of produce. Both of these creatures, crabs and spiders, use their exoskeleton as protection from the outside world, they both molt this skeleton as a way to physically grow (it can also repair damaged limbs), and they both use their jointed limps to more easily maneuver in loose substrate, sand or dirty, and also better maneuver over obstacles, rocks and branches or whichever else might be in their way. These two split off from a common ancestor, one became land based while the other stayed water based, and developed along similar lines of evolution.
An example of Analogies would be the fins of sharks and dolphins. Sharks are Cartilaginous and dolphins are Mammals. Sharks are among the oldest living animals, they date back 450 million years, they are predators that typically eat other sea life, they are cartilaginous which means they’re made of cartilage (I.e their ‘bones’), and as a fun fact they have to constantly keep moving so they can filter water through their gills and receive oxygen. They are found all over the world from deep to open seas, from warm water to under arctic ice, they also can be seen migrating for food and breeding. Despite popular theory, they don’t typically go after humans specifically. Most shark attacks are because a human got too close or the shark mistook the human for a seal, or other food animal. Dolphins on the other hand are mammals which means they do have hair (typically born with it on their ‘nose’), they also eat fish and squid, and they are some of the smartest animals (below humans) and they have been seen using tools such as sponges and mud. They travel in packs called Pods and are very social animals. They are also found around the globe from oceans to rivers. Both of these animals are water based animals, though dolphins breathe through their blowholes while sharks filter oxygen through their gills, and so both of these creatures use their fins as a way to swim faster. Even though the sharks are made of cartilage and the dolphins are made of bone, they both use these fins as ways to propel themselves. Despite them being from two entirely different classes, mammalian and Cartilaginous, they both developed fins that can be used to propel themselves quickly through the ocean. Both animals needed a way to travel faster, to catch prey or avoid predators, and thus both evolved independently of each other due to the same environmental factors.
Whoa, I did not realize that sharks and dolphins were so different! I also did not expect someone to use those two species for an analogous trait comparison. So these creatures are completely different yet there fins work in the exact same way, thats crazy.
ReplyDeleteMy kingdom for a paragraph break! :-) Seriously, though, these are blogs but they should still be treated as papers, complete with correct formatting and breaking topics/prompts into separate paragraphs. It is very difficult to parse out where you address the different questions. Don't make it hard for me to grade your work.
ReplyDeleteJust an opening clarification with regard to this statement:
"An example of a homologous animals would be crabs and spiders. "
Animals cannot be homologous! We can only compare their *traits* to see if they are homoloogus, analogous, or just common inherited traits. Understand that important distinction.
Homology:
1. (5/5) - Good description of your two species.
2. (2/5) - I'm unclear which trait you are comparing here. You offer a broad description of both species but don't focus on one trait in particular and don't explain how the structural differences result from functional/environmental differences, which was the focus of this section and the way to explore homologous traits. Instead you seem to focus on *similarities* in traits (and they do have quite a few).
So can you identify a trait that these two organisms share that express differences that can be explained by their environmental differences? I'm afraid these organisms are outside of my wheelhouse of specialties, so I'm not sure if I can figure out a homologous example with them
Another student used crabs in their homologous section but compared them to lobsters, specifically the differences in their front set of limbs and their claws. These are distinctly different and allow you to understand why those differences exist in terms of function and environmental pressures. Recognize that the emphasis here is studying the DIFFERENCES in structures between to species who share traits that arise from common ancestry, instead of comparing structural similarities.
3. (3/5) - "These two split off from a common ancestor, one became land based while the other stayed water based, and developed along similar lines of evolution.
Yes, and you are correctly identifying their different environments but you never explain their structural differences due to these environmental differences.
And recognize the goal for this prompt was to explain how the specific traits in question arose from that common ancestry even though they exhibit differences in structure due to divergent evolutionary pressures. You never focus on one set of traits and you focus on similarities, not differences.
4. (5/5) - Good images, though recognize that the crab is a cooked one. :-) Their shells only become red when you boil them. Check out the link below:
https://sabrinacurrie.com/wp-content/uploads/2023/04/1-8.jpg
Analogy:
1. (5/5) - Good description.
2. (5/5) - Very good and these ARE an example of analogous traits arising from convergent evolution.
3. (3/5) - You don't really draw this connection here, using ancestry to confirm that these traits are the product of convergent evolution and not common ancestry. Let's walk through this a bit. The common ancestor of the dolphin and shark is an archaic fish, who did possess these fin structures and also passed that trait onto extant shark species. So the question is, did the dolphin also inherit it's fin from that common ancestor? Dolphins "fins" evolved after dolphins split off from terrestrial mammals, i.e., long after the split with ancient fish. This provides us with the evidence we need to confirm that this trait did evolve independently in at least one of these organisms, making these traits analogous.
4. (5/5) - Good images.
You have some confusion over these concepts, particularly the homologous traits. I recommend reviewing a few student posts to get clarification on this. In particular, I recommend reviewing posts by Ishan, Matt and Spencer. Just make sure to read my comments on their posts for any clarifications and corrections.