| Why whales cannot breathe in water?|
|Question Date: 2013-08-19|
Whales can’t breathe in water for the same
reason we can’t. We have lungs and not gills.
Lungs work fine on land because there is a lot of
oxygen in air. About 20% of air is oxygen. Water
has a lot less oxygen in it. The amount depends
on things like water temperature, depth, and
salinity (the amount of salt in the water).
Oxygen moves from the environment into the
animal over surfaces on gills or in lungs. The
lower the oxygen concentration, the more surface
area the animal needs. Imagine that you needed to
catch fish. If the fish were all close together,
you could use a small net. If they were spread
way out, you would need a bigger net. Animals
that breathe water need a big “oxygen net.”
If you had a really big net and a small space to
store it, what would you do? You would probably
fold it up. Gills are big oxygen-catching
membranes that are folded up, but the folds can’t
be squashed onto each other. They have to be
touching the water so that they can catch the
oxygen out of the water. Fish gills have tiny
folds, which are folded into small folds, which
are folded into larger folds. You can see gill
gills. This gives them a big surface area for
catching oxygen that fits into a small space.
Gills don’t work in air because all of these
folds collapse into each other when they are not
floating in water. Amphibians like frogs usually
lay their eggs in water. Young frogs are called
tadpoles or pollywogs. They live in water and
have gills. As they grow up, they grow legs and
lungs and they lose their gills. When other
amphibians evolved into land animals hundreds of
millions of years ago, they developed lungs.
Lungs have little air pockets that don’t collapse
in air. These pockets are called alveoli and you
can see pictures here:
here to see.
Reptiles, birds, and mammals have lungs with
alveoli. Whales are mammals, so they have lungs.
If they tried to breathe in water, the low-oxygen
water would just fill the little air pockets,
blocking the high-oxygen air from getting in. The
whale would drown.
Why do you think whales have blowholes? Do you
know that they are just nostrils on the top of
Thanks for asking.
Whales cannot breathe underwater because they
do not have the appropriate respiratory system to
do so. To breathe underwater, they would require
gills, which exchange the carbon dioxide and
oxygen dissolved in water.
Great question! Whales can't breathe underwater
for the same reason that you and I can't breathe
underwater. Whales and people are mammals. The
earliest mammals lived on land, and therefore used
lungs for breathing (as do reptiles and
amphibians). Over time, however, some mammals,
including whales, transitioned to living in water.
Other mammals that underwent similar shifts to
living in water include seals and manatees. Since
the ancestors of these aquatic mammals had lungs,
that's the breathing system they're "stuck"
with--that is, no animal that we know about has
been able to "re-evolve" gills--which is how
sharks, tunas, goldfish, etc. breathe. Animals
with backbones lost their gills and developed
lungs when they moved onto land. Those back-boned
animals that returned, millions of years later, to
living in water, maintain the breathing system
(lungs) of their land-living cousins.
Whales cannot breathe underwater because they
are mammals and not fish. This means that their
breathing organs are lungs, rather than gills. So,
like humans, whales need to come to the surface to
take a deep breath of fresh air and when they are
underwater they hold their breath.
A previous ScienceLine answer explained why
whales are able to hold their breath for
especially long times compared to humans:
here to read
Fish also need oxygen to breathe. Fortunately,
there is always a small amount of oxygen mixed
into water. Fish gills separate the oxygen from
the water very efficiently and pass the oxygen
into the blood of the fish. This is how a fish
That´s a terrific question! Whales are mammals
just like you are (they have hair, feed their
offspring milk, and maintain their body
temperature). Whales cannot breathe in water
because they need to get oxygen from the air, so
they have to come up to the surface to breathe.
You may know that fish also need oxygen, but they
get their oxygen out of the water directly, in the
form of dissolved oxygen. Why can´t whales also
get their oxygen directly from the water? It
turns out that whales are descended from other
mammals that evolved on land, and these land
mammal ancestors were breathing oxygen from the
air using their lungs (like us). Whales and other
marine mammals have kept this trait, even though
they now live in the sea.
In case curious, fish breathe dissolved oxygen
in this way: water passes over the fish gill
system through extremely fine membranes. These
gill membranes are made up of very small blood
vessels that can take up the dissolved oxygen as
the water moves past them. That´s why fish (unlike
whales) cannot breathe outside of water - they
need the water to move over their gills to absorb
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