How do Fish Breathe? Video Lecture | Science Class 7

Squeaks and I are adopting a pet goldfish!
He lives in a fish tank, and he’s a great
swimmer!
In fact, this little guy’s whole body is
really suited to life in the water.
He has great fins to help him swim, and eyes
that can stay open in the water.
These special body parts help him to live
in his underwater home, so we call them adaptations.
There’s one adaptation that’s really important
for our new fish friend to survive in a fish
tank or pond.
He needs to be able to breathe underwater.
People can’t breathe underwater because
there’s no air.
We have to hold our breath, or use special
equipment like scuba gear to get air.
But our goldfish isn’t holding his breath,
and he didn’t bring scuba gear!
Instead of breathing air, he actually breathes
water.
Humans, fish, and all kinds of other animals
have to breathe for the same reason: we all
need something called oxygen.
Even though air might not seem like it's made
of anything, it's actually made up of lots
of tiny things called molecules that are way
too small for you to see.
Oxygen is one of the ingredients in air, and
it's really important: it helps your body
make energy!
You need oxygen to break down your food, move
your muscles, and even just to think with
your brain.
There's oxygen in air, but you need it to
get into and all around your whole body!
So, you have special organs called lungs to
help get that oxygen.
When you breathe in, you can feel your lungs
expand full of air, just like a balloon.
Once they’re full of air, your lungs pull
the oxygen that you need out of the air before
you breathe out.
That oxygen goes into your blood and travels
all throughout your body.
There’s air all around us, so as long as
you we breathe, you can get oxygen.
Land animals can have all different shapes
and sizes of lungs, but animals that live
underwater, like fish, need oxygen, too!
Fish don’t have lungs, and there isn’t
any air around them.
Animals like our goldfish need to use another
way to get their oxygen.
And guess what?
Water is full of oxygen, just like the air
is!
So fish can get their oxygen straight from
the water they live in.
They just need an adaptation to get the oxygen
out of the water.
Instead of lungs, most underwater creatures
have another special body part that allows
them to pull oxygen straight out of the water,
called their gills.
Gills look like little slits on either side
of a fish’s face.
A fish’s gills work a lot like our lungs.
When a fish pulls in water through its mouth,
the water goes back out through its gills.
As the water runs through the gills, it goes
right past the fish’s blood.
The oxygen in the water flows into the fish’s
blood, and now the fish can use the oxygen
all over its body!
The fish is basically breathing water with
gills, instead of air with lungs.
Other types of animals besides fish use gills,
too.
Crabs, lobsters, snails, and even some bugs
use gills to breathe!
So, even though we both have very different
ways of getting it, our goldfish needs oxygen
just like I do.
Isn’t that right, little fish?
What do you think we should name our new fish?
Ask a grown-up to help you leave a comment
below, or you can send us an email at kids@scishow.com
Thanks, and we'll see you next time here at
the Fort!