Classifying Ocean Animals
Classify ocean animals into major groups: fish (breathe through gills, have scales), marine mammals (breathe air, warm-blooded, feed milk), and invertebrates (no backbone — jellyfish, octopuses, crabs, starfish)
What a learner can do afterwards
- Sort ocean animals into fish, marine mammals, and invertebrates
- Give defining features of each group (gills vs lungs, backbone vs none)
- Correctly classify at least two animals in each group
The lesson
Every ocean animal fits into a group of animals with the same kind of body. Three big groups are fish, marine mammals, and invertebrates. Some ocean animals belong to smaller groups, like the reptiles. A sea turtle is an ocean reptile. To find the right group, look at how the animal breathes and whether it has a backbone.
A tuna is a fish. Fish breathe through gills, slits on the side of their head that pull oxygen out of the water. Fish also have scales, small hard plates that cover their skin. Sharks and clownfish are fish too.
A seal is a marine mammal, just like the whales and dolphins you already learned about. Marine mammals breathe air through lungs, so they swim up to the surface again and again. Their bodies stay warm even in cold water, and mother marine mammals feed their babies milk.
A jellyfish is an invertebrate. Invertebrates have no backbone at all. Octopuses, crabs, and starfish are invertebrates too. Some have a soft body and some have a hard shell, but none of them have bones inside their bodies.
Ask two questions to sort the animals in these three big groups. Does it breathe air or water? Does it have a backbone? Air and a backbone means marine mammal. Water and a backbone means fish. No backbone at all means invertebrate.
Fish have gills and scales, marine mammals breathe air and feed their babies milk, and invertebrates have no backbone at all.
Watch it
Where it sits
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Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.