If the cell membrane were not selectively permeable, then unwanted substances would transfer through instead of being blocked out. Think of it like this: you have a sifter with various sizes of spice in it. You only want the finer grains of spice in your food, so when you shake the sifter, the larger pieces of spice don't fit through the small holes that only allow fine grains. Then you are left with the small spices in your food and the large ones stuck in the sifter.
Hopefully this helps and I wasn't too confusing :)
Answer:
Fossils are formed in a number of different ways, but most are formed when a plant or animal dies in a watery environment and is buried in mud and silt. Soft tissues quickly decompose leaving the hard bones or shells behind.
Explanation:
Hi there!
With humanity's constant burning of fossil fuels, large amounts of carbon dioxide get pumped into the atmosphere.
Under normal circumstances (without humans), greenhouse gases are good, as they help keep heat energy in, much like a blanket.
Now, with such large amounts of carbon dioxide, too much heat is being kept inside of this blanket. Our ice caps are melting, threatening the survival of many species of animals. Along with their melting, sea levels are rising (and will keep rising).
With our increasing population, the last thing we can afford is to lose land as well.
Hope this helps.
:)
The same mass of molecules takes up more space when frozen, ice is less dense than liquid water. For this same reason, water below 4° Celsius becomes increasingly less dense as it gets colder.