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I'm sure this is already out there but I was watching the History channel and they were talking about how 650 million years ago the Earth was one big ice ball then it began to break up due to volcanic activity. Well cells need like 85% water inside and outside in order to develop, salt water fish have evolved to cope with that same with Fresh Water, so my biology teacher was saying that life had to have been made at the mouth of a river and evolved its seperate ways.


Well we know that Volcanic activity can create Amino Acids which are the building blocks for life. IF Volcanos broke up Snowball Earth it would have deluted the world as the ice melted. Thus you have the solution needed for the birth of life and those original amino acids and boom your explosion of life which happened 600 million years ago.

What do you guys think? Plausable?

I like it! Look into it for us.

Hmmm... interesting, and plausible. However, if saltwater organisms could have evolved from freshwater ones, why couldn't that osmotic gradient evolve the other way as well? Either way, they're not compatible in the final product - I don't see why the osmotic ability of a cell membrane couldn't develop either way with equal likelihood.

Gary Roberts needed a place to play hockey... so he created the Earth and put life on it. Doesn't anyone know wanything?

It's plausible, but unlikely. Mikey pretty much hit the nail on the head there.

The earliest known life is a bit older than 600 million years.

http://en.wikipedia.org/wiki/Fossil_rec ... rous_sites

Plus, the earliest known life more resembled a mdoern cell component - a mitochondria - than a modern cell itself. The content may or may not be approx. 85% water.

Seriously, Monroe - if you get a chance, ask your teacher why he presented the idea that the osmotic ability of cell membranes could only develop in one direction. I'm not being a smartass - I'd really like to know if there is a reason.

Mikey wrote:Plus, the earliest known life more resembled a mdoern cell component - a mitochondria - than a modern cell itself. The content may or may not be approx. 85% water.

Seriously, Monroe - if you get a chance, ask your teacher why he presented the idea that the osmotic ability of cell membranes could only develop in one direction. I'm not being a smartass - I'd really like to know if there is a reason.

*digs up notes*

In osmosis the cell is trying to keep the hypotonic saline solution. My notes say that the fresh water dellutes cells. This is why Fresh Water fish have great kidneys.

In a hypertonic saline solution the cells have too much salt outside so they want to keep what they have inside.

Isotonic (that's the word I was looking for) is the right equilibrium cells want. Since osmosis is probably an evolved trait early life would have had to have developed in an Isotonic Saline Solution. This you'd get from the delluted world oceans as the huge ice age of 650 million BC melted.

If the relative salinity of cells never changed, then yes. My questions is, if cells have evolved that have an osmotic gradient based on a hypotonic environment - fresh water - why couldn't they have evolved to have the osmotic gradient in the other direction?

Fresh water is NOT isotonic for modern life. There is far more salinity in a living multicelleular organism than there is in non-saline water.

Well, that arises from the very definition of osmosis. Osmosis is the spontaneous movement of water across a semipermeable membrane from a region of low solute concentration to a solution with a high solute concentration down a solute concentration gradient. The movement of the solvent is always from the less-concentrated (hypotonic) to the more-concentrated (hypertonic) solution. My classmistress was a professor of biology and a very strict one; I have to know this "in the middle of the day and in the middle of the night" as we say it in Croatia.

hmm, well I talked to my bio teacher and he said it was a possibility. He for one thinks life was around much older than that but was wiped out and then reevolved. He's been teaching for 35 years whereas I'm only in bio101 So I'm sure I screwed up on the properties of hypo and hypertonics. I was under the impression that cells that are hypo or hyper want to become Isotonic so it makes the most sense for cells to have evolved in an isotonic state.

cells that are hypo or hyper want to become Isotonic

generally, yes.

so it makes the most sense for cells to have evolved in an isotonic state.

Unfortunately, there is really no such place for a multi-systemed creature. We can't live in an over-saline environment, because of the negative effects on circulation, excretion, endocrine action, etc.; but we are by nature hypertonic to our environments because of the presence of things like electrolytes, neurotransmitters, hormones, enzymes, etc. Remember that if a compound is neither acid nor basic, it's most likely a salt.