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Explore the underwater world and how marine life survives in salt water.
Imagine you are a tiny fish swimming in a giant bowl of salty soup! How do you breathe underwater without a snorkel, and where do you go to take a nap?
The ocean is a massive habitat. A habitat is a natural home for plants and animals. Unlike the water you drink from a tap, ocean water is saltwater. It has lots of salt mixed in! Most ocean animals need this salt to stay healthy. If you took a tiny sip of the ocean, it would taste very, very salty. Because the ocean is so big, it is home to millions of different living things, from the smallest shrimp to the biggest blue whale.
Quick Check
What is the main difference between ocean water and the water in your bathtub?
Answer
Ocean water is saltwater, which means it has a lot of salt in it.
Fish have amazing bodies that help them live under the waves. Instead of lungs like you, they have gills. Gills are special slits on the side of their heads that take oxygen out of the water so they can breathe. To move around, they use fins. Fins act like oars on a boat, helping the fish push, turn, and stop. A fish might have tail fin and or more side fins to help it steer through the deep blue sea!
Let's look at a goldfish to see how it works: 1. Look at the slits behind its eyes; those are the gills for breathing. 2. Watch the flaps on its back and sides; those are the fins for balance. 3. Watch the big fin at the back; that is the tail used for speed.
Quick Check
Which part of a fish works like a human's lungs?
Answer
The gills.
Just like you have a house, fish need a place to stay safe. Seaweed is a tall plant that grows in the water. It looks like an underwater forest where fish can hide from bigger animals. Coral looks like colorful rocks, but it is actually made by tiny animals! Coral reefs are like busy underwater cities. They have lots of little holes and cracks where fish can sleep and stay protected from the wind and waves above.
Imagine a small yellow fish is being chased by a bigger fish. 1. The yellow fish sees a patch of tall, wavy seaweed. 2. It swims inside the leaves where it is hard to see. 3. The big fish swims past because the seaweed hid the little fish perfectly!
A coral reef is a very crowded place. If a reef has small holes and fish are already sleeping inside, how many holes are left for new fish?
There are spots left in the coral 'apartment'!
What do fish use to breathe oxygen from the water?
Which of these is a 'saltwater' habitat?
Coral reefs are made by tiny animals and provide homes for fish.
Review Tomorrow
Tomorrow, try to explain to a friend how a fish uses its fins and gills to move and breathe.
Practice Activity
Draw a picture of an ocean habitat. Include at least one fish with fins, a patch of seaweed, and a piece of coral.