Analogy & Homology

Analogy and Homology in Water Species 

Great White Shark

Humpback Whale

Bottlenose Dolphin

When perceiving at these three sea animals, you can notice that all three of them have fins, dorsal, tail, and flippers. Despite these similarities only two of these species are ancestral similarities. 

Homologous Traits

Bottlenose Dolphin 

The Bottlenose Dolphin is a sea mammal who swim in schools and hunt their food by corralling the fish in large swirls of fish herds. They swim in schools together and are intelligent animals who are generally friendly with humans. They throw their fish into the air and catch them as they fall into their mouths. This is done repeatedly until the school has had their share. 

Humpback Whale

The Humpback Whale is the largest known mammal in the world who swims across the ocean in pods, not schools, and stay with each other till death. Despite their size, that is their only defense when it comes to predators. They are not equipped to hunt or attack of any predators, not like they have any, but this changes the way they hunt. They are carnivores, but if they cannot hunt they simply allow the krill they eat to enter their mouths for them to consume as they swim across the ocean. 

Teeth

Humpback Whale

The Humpback Whale is a sea mammal that is also considered a carnivore just like the Great Whiteshark, but their teeth are ultimately extremely different. You see, they don't really have teeth but something called baleen. These rows of baleen are used to capture and trap thousands of krill and shrimp they come across. They do not hunt, but instead simply capture. The baleen are hairy likes teeth akin to finger nail material that ensnare the krill and traps them so that they cannot escape.  

Bottlenosed Dolphin

The Bottlenosed Dolphin is also a carnivore, but their teeth are more closely related to the sharks rather than the whale's baleen. Dolphins only use their teeth to chew their prey, and use other methods to hunt fish. And since they can hunt, Dolphins do not have Baleen like Whales. 

Common (General) Ancestor

The Whale and The Dolphin both have the common ancestor of the terrestrial Cetartiodactyla that stem from the artiodactyl family. These mammals were even toed carnivorous artiodactyl, but the fact that they were carnivores is the point here. That being that generally, the artiodactyl are herbivores and deer-like, so the classify the whale and the dolphin in this group would be close, but not cigar. However, the teeth of the dolphin and the whale do come from this family, the way the Humpback Whale's baleen developed is due to other changes and not their ancestor. The Whale's Baleen is the only species on earth that is known to have this filter system, so where they got this from isn't entirely known by biologists. 

Cetartiodactyla

Analogous Traits

Great White Shark

The Great White Shark is a Carnivorous Fish who hunts large fatty mammals such as penguins, seals, large tuna, and such. They are predators that attack and swim in small schools, but they hunt them as if they are similar to that of predators on land such as large cats. They stalk and hunt their prey before eventually attacking. They swim in the ocean at high speeds and are aerodynamic in structure. 

Bottlenose Dolphin 

The Bottlenose Dolphin is another sea animal who swims in the ocean with a similar aerodynamic structure to a Great White Shark. They need to swim through the ocean to get where they need and to swim after prey. The main reason for their shape is to allow them to swim freely in the ocean. 

Anatomy 

Great White Shark

The Great White Shark is a large predator who swims in schools and is dynamic in structure, they have dorsals, fins, flippers, and a tail. Their skeletons are made completely of cartilage to allow for more smooth swimming and flexibility when traveling in the ocean. They are also not mammals, so they have gills to take in oxygen rather than lungs. 

Bottlenosed Dolphin

Structurally the teeth of the dolphin and shark seem similar, but are very different. Dolphins' bones are made up of bones and not cartilage like sharks. They however do have dorsals, fins, flippers, and a tail in a similar shape to that of the shark. These structural similarities are solely because of analogous pressure of living and evolving in the ocean. They are needed to successfully populate in their current environment.

Differences

Under their exterior are their bone structures. The shape of their exterior limbs may looks the same, but as stated before their bone anatomy plays are large role in the reason as to why the similarities are analogous. Sharks are made of cartilage and Dolphins are mammals, so they are made up of bones. However, because they are mammals the bone structure (not just material) are also different. The bones of a dolphin show signs of being descended of mammals, as the sharks are quite obviously descended from fish. 

Shark (top) - Dolphin (bottom)

Common (General) Ancestor

If you go back far enough the closest ancestor you may find that a dolphin and a shark share is the lobe-finned fish. This fish is considered to be the ancestor for nearly every single type of species from millions of years ago. This however does not mean they are similar from genetic descent because the evolutionary line for these two split off where the dolphins ancestors head to land and the shark stays in water. The lobe-finned fish developed into an amphibian like creature who then went on to be a mammal, bird, reptile etc. This is the most common ancestor there is to them, but even then this may not even be the case, because the lobe-finned fish is the ancestor for mammals, birds and reptiles, not fish. The Ray Finned fish is more genetically similar to the shark than the lobe finned fish structurally, so the similarities between the Great White Shark and the Bottlenosed Dolphin is analogous and not genetic.