Why are sharks fish?
In: Biology
Shrimps and crabs belong to a group called crustaceans. They have hard external skeletons and jointed legs, while fish have internal skeletons and fins. Crustaceans breathe with gills under their shells, whereas fish have gills on the sides of their heads. Crustaceans walk or crawl using their legs, while fish swim with their fins. Lastly, shrimps and crabs are arthropods (like insects and spiders), while fish are vertebrates, meaning they have backbones.
Fish are vertebrates with gills, fins, and skulls, but no limbs. That’s how we(science) chose to define the taxonomic category of “fishes.”
Crabs and Shrimps are invertebrates. Therefore, they are not Fish.
Why are you not a fish, OP?
Vertebrate vs invertebrate is strongly used as a distinction in taxonomy. Fish have backbones. So do sharks. So sharks can be ‘fish’.
Shrimp and crabs have no backbone, so they are not considered ‘fish’.
Sharks are closely related to other fish in evolutionary terms and biology, while crabs and shrimp are not.
Its pretty similar to why Frogs and Salamanders are both amphibians, even though they can look very different from each other.
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