I’m writing up a list of misconceptions that people (particularly high schoolers) have about classifying animals. I would love to hear what animals you think people often confuse or misplace (e.g., “A dolphin is a fish!”). Give me your best confusing organisms! (Plants are good too).
Here is my list so far. Please correct me if you see any mistakes, and I would love to hear any additions!
Invertebrates:
Jellyfish: this is a cnidarian. Most students think it is a fish because it contains the word “fish.” Remind students that fish are way more complex. Fish have a head, brain, bilateral symmetry, digestive system, blood, endoskeleton, and vertebra. A jellyfish has none of these things.
Starfish: this is an echinoderm. Most students think it is a fish.
Scorpion: this is an arachnid. Some students think it is a reptile, because it lives in the desert with lizards and snakes.
Harvestmen: this is an arachnid. Students often call it a “Daddy long legs,” but it is not to be confused with spiders, which are a different category of arachnids.
Vertebrates:
Seahorse: this is a fish, and most students understand this. A few students think that it is in a different category than “fish” because of it’s unusual appearance.
Shark: this is a fish, and most students understand this. A few think it is a mammal because it is similar to a dolphin. This is a good way to bring up convergent evolution and analogous structures.
Salamander and newts: these are amphibians. A newt is a type of salamander. Many people think there are separate categories, but a newt is a subcategory of a salamander. People often think salamanders and newts are reptiles because of their lizard-like appearance. However, they are amphibians because they lay soft-shelled eggs in the water, go through metamorphosis, are cold-blooded, and do not have claws.
Frogs vs toads: these are amphibians. Many people think they are separate taxonomical categories, but actually a toad is a subcategory of frog. Toads tend to have drier skin and shorter legs than other types of frogs.
Turtles and tortoises: this is an aquatic reptile. Many students classify it as an amphibian because it is sometimes green and it lives in the water. They also forget that turtles have scales, and they think it has smooth skin like a frog.
Students may also not know the difference between a tortoise and a turtle. Many people think they are separate categories, but a tortoise is actually a subcategory of turtle. “Turtles” are an order, while “tortoises” are a family belonging to that order.
The order of turtles have a defining characteristic of a shell, which forms from its ribs. Other reptiles do not have a shell.
A tortoise is a type of turtle that only lives on land. Typically, tortoise shells are rounder than other species of turtles. Other turtles typically have flatter shells that streamline it for swimming**.**
Ichthyosaurs: this is an unusual category of extinct marine reptile. When students see it, they often think it is a fish (like a shark) or a mammal (like a dolphin). It is confusing since they gave live birth (like a mammal) and they have flippers (like a fish). It is not a fish because it did not have gills—instead, it came up to the surface to breathe, like reptiles or mammals. It is not a mammal because there was no fur, hair, or mammary glands present.
Crocodile and alligators: this is a reptile (specifically, an archosaur with a gizzard and 4-chambered heart, which are traits that make it a little more complex than turtles and lizards). Some students would accidentally classify it as an amphibian because they see it both in the water and on land. Sometimes they classify it as a mammal because of its large size.
Pterodactyl: this is a flying reptile (specifically, an archosaur). Many students classify this as a bird because it flies.
Students sometimes think that birds evolved from pterodactyls, but birds would’ve evolved from theropods (which includes T-Rex, velociraptor, oviraptor, etc.) Wings start a good discussion on convergent evolution and analogous structures.
T-Rex: this is a reptile (specifically, an archosaur). Because dinosaurs are extinct, students often don’t put them in the same schema or mental category as living creatures. They might say, “Dinosaurs are extinct and in their own category, they don’t belong to reptiles.”
Because some students have heard that birds evolved from dinosaurs, some students would put T-Rex into a “bird” category. However, a bird would be a subcategory of dinosaur, but a dinosaur would not be a subcategory of bird.
Manatee: This is a mammal. Many students have never heard of a manatee, sea cow, or dugong. It’s a good idea to include a picture of a manatee when discussing it. Because it is aquatic, some students are tempted to classify it as a type of large fish.
Dolphin: this is a mammal, which most students understand. A few would classify this as a fish, similar to sharks.