Life started in the oceans and from the first simple organisms, many creatures evolved. They all had to face the challenges of an environment with little oxygen, lots of salt and, in the depths, lots of pressure.
If you are salty inside and your surroundings are as salty as you, you are fine. But if the water around you has much more or much less salt than you, you have to work hard to prevent water from following the salt, as it does.
To visualize this, we stripped an egg of its shell (with vinegar!) Ouch! said the egg.
Then we put a few poor naked eggs in cups with different amounts of salt. This is what happened to them.
The one in the middle is our original naked egg. Isn't it pretty?
On the left is an egg left overnight in distilled water--no salt. Since the inside of the egg is saltier than the water outside it, the water rushes in (remember osmosis?) and makes it bloat.
And what about the poor thing on the right? When you place an egg in extremely salty water (or in corn syrup), the water inside the egg moves out, through osmosis again, making the egg look like a dry prune.
This gives you an idea of what organisms have to deal with when living in the water.
How do they do it? We talked about that at length and we found pretty interesting strategies out there!
Did you know there's nothing like playing with a naked egg? Try it yourself.
Enough of playing with naked eggs!
Aquatic animals also have to deal with buoyancy. They want to control when they sink to the bottom or float to the surface. And some do! With a swim bladder. How do you study a swim bladder? You make your own glass-bottle bladders.
Glass-bottle bladders at work!
And don't forget that the deeper you go in the ocean, the heavier the weight of the column of water above you. That can be a lot of pressure. The cup on the right was exposed to that kind of pressure... in a pressure cooker.
That's it for this week. Stay tuned for more!