Posts tagged ‘Oxygen’

How can fish breathe in water?

Fish breathe with gills, which are inside the fish’s head on each side of its throat.  The gills are made of a thin material that allows the fish’s blood to come close to the surface of the gills.  Water contains large amounts of oxygen.

When a fish breathes, it takes a mouthful of water, and then closes its mouth.  This forces the water pass the gills.  The oxygen in the water is absorbed through the think surfaces of the gills, and into the fish’s blood.  The water then leaves the fish’s body through narrow gill slits on each side of its heard.–Dick Rogers

Can fish drown?

Fish can drown under certain conditions.  It is not the water that keeps fish alive, but the oxygen in the water.  Fish breathe oxygen, just as we do.  The water contains oxygen that comes from the air or is given off by water plants.

A fish takes the oxygen out of the water by means of its gills.  When a fish is placed in a small tank of water, however, it may soon use up all the oxygen that is in the water.

If this happens, the fish suffocates.  This is why, if you keep pet fish, you must change the water frequently in order to give them a fresh supply of oxygen.–Dick Rogers

Why fish don’t sink?


A fish, with its bones and scales, is heavier than the water it displaces. Under normal circumstances, it would tend to sink.  But most bony fishes have a balloon-like sac inside their bodies called an “air bladder” that acts as a float to keep them from sinking.  The air bladder fills up with some of the oxygen dissolved in the fish’s blood.

Some fish, such as pike and catfish gulp air at the surface of the water to fill their air bladders.  A shark has no air bladder to buoy it up.  It must constantly be swimming in order to keep from sinking. – Dick Rogers

How do frogs stay under water so long?

When under water, a frog takes in oxygen through its skin.  When a frog dives under water, he does not come to the  surface as quickly as you have to when you dive.  Why not?

Frog swimming underwater

The frog, of course, cannot breathe under water, as it did when it was a tadpole.  When a frog is on the bank or pond, it breathes with its lungs, which are somewhat like your lungs.

There is always some air mixed with water in the pond.  When the frog is under water, it can take a little of the air it needs through its skin.

This explains why the frog can stay under water all winter.

If you live where the winters are cold, you’ve probably noticed that the frogs seem to disappear when cold weather comes.

Many frogs dive into ponds and bury themselves in the muddy bottom, and quickly fall asleep.  Sleeping all winter is called “hibernation.”

While the frog is sleeping, its body keeps so still that it can get along without any fresh air until it wakes in the spring.  During its winter sleep, the frog lives on the food stored in its fat body.  – Dick Rogers

How does a firefly make its light?


A firefly’s light comes from a special organ on its body.  Luminescent cells within the organ produce chemicals which join with oxygen to make the light.

On a summer evening, you may see the bright, little flashes of a firefly’s light.

The firefly is not really a fly:  it is a beetle.  Its blinking yellow light comes from a special luminescent organ which is usually located at the end of its body.

To flash its light, the firefly admits air into its luminescent organ through tiny openings.  Inside the organ are light-making chemicals.  When oxygen in the air joins with the chemicals, energy is released in the form of light.

A firefly doesn’t burn in your hand if you catch it.

Fireflies find their mates by flashing their lights.  As he flies about at night, the male flashes his light.  The female seldom files, but parches on a blade of grass near the ground.  When she sees the male’s blinking signal she flashes her own light.

The fireflies flash their lights until they finally meet. – Dick Rogers