Sorting ocean animals into groups

Science · Ocean Life · ages 7-9

Name ______________________ Date ____________

Which of these is a marine mammal?
- Tuna
- Seal
- Jellyfish
Which body part helps a fish breathe underwater?
- Lungs
- Gills
- Skin
A starfish has a backbone.
Circle one: True False
Which clue tells you an animal is a marine mammal and not a fish?
- It lives in the ocean
- It breathes air and feeds its baby milk
- It has scales
An octopus has no backbone and a soft body. Which group does it belong to?
- Fish
- Marine mammal
- Invertebrate
Which pair are both invertebrates?
- Crab and jellyfish
- Crab and tuna
- Jellyfish and seal
A dolphin breathes air, feeds milk to its baby, and stays warm in cold water. Why isn't a dolphin classified as a fish, even though it lives in water and looks similar to one?
- Because it breathes air and feeds milk, both mammal traits, not fish traits
- Because it's bigger than most fish
- Because it swims in salt water
Milo says a shark is a mammal because it is big and swims fast. What is wrong with his thinking?
- Size and speed don't decide the group; a shark has gills and scales, so it's a fish
- Sharks are actually invertebrates
- Milo is right, sharks are mammals

Answer key

For grown-ups. Fold this page away before handing over the rest.

Seal · A seal breathes air and feeds milk to its baby, just like other mammals.
Gills · Fish use gills to pull oxygen out of the water around them.
False · A starfish is an invertebrate, so it has no backbone at all.
It breathes air and feeds its baby milk · Fish and marine mammals both live in the ocean, but only marine mammals breathe air and make milk for their babies.
Invertebrate · No backbone means it's an invertebrate, along with jellyfish, crabs, and starfish.
Crab and jellyfish · Crabs and jellyfish both have no backbone, so they are invertebrates.
Because it breathes air and feeds milk, both mammal traits, not fish traits · Body features like breathing air and making milk decide the group, not size or where the animal lives.
Size and speed don't decide the group; a shark has gills and scales, so it's a fish · Sharks breathe through gills and have scales, which makes them fish, not mammals.