Iv got something that challanges evolution a little bit

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Im sure someone else has brought this up. Iv been thinking this through every once in a while for a year or so. Lakes are isolated from other lakes, am I right? Then why are there the same species of fish in other lakes? I know, a lot of fish are stocked into lakes but Im talking about naturally before man stocked them. Ya, mull that around in your head.

Ever heard of Lake Vostok? o_o

I think it has to do with the landscape changing...like how they find similar fossils where Africa and South America were theoretically together. I'm not sure though.

What about it? And if its about it has unique organisms I really dont care. Explain that about all the other lakes then.

I'm no geologist but some continents move at different rates... that could be a cause.. Antarctica hasn't moved in quite a while...

How so? How does that make fish of the same species appear in multiple lakes?

I don't know about other parts of the world, but in the Midwestern US, very few lakes are truly landlocked. Most have streams or rivers or creeks connecting them to other bodies of water. Wetlands were also much more widespread than they are today, if you read the early settlers accounts of the Great Lakes regions you will find numerous references to swamps. So there may have been passages for fish to use that have since dried up or otherwise disappeared.

Take my appifany and destroy it.......damn

Water levels change very frequently (over long periods of time), just as continents and islands become separated by water. The same species may be found on two separate continents or in two separate bodies of water. A one point the two landmasses or lakes would likely have been joined so that one species could populate them, they would have only become separated later.

Short answer: I have no idea.

Long answswer: I don't make the rules, kid.

This is quite interesting, and I've read a few things you may wish to find out more about. Firstly, the distribution of fish species across northern Europe from mainland europe, to England to Ireland. The indigenous diversity of species decreases in that order and is related to the retreat of the ice sheet at the end of the last glaciation and the sea covering landbridges (with associated freshwater migration routes) between those land masses. Unglaciated mainland Europe provided what was basically the reservoir of diversity that restocked the UK waters after the ice had gone. So how did the fish get into what are now landlocked waters? Some mechanisms have been mentioned, including rivers that used to be fed from the melting ice no longer flowing, or changing course. As ice sheets retreated crustal isostatic rebound would have changed gradients, even reversing them, causing rivers to flow along different routes, feeding certain lakes for a period, then abandoning them to flow along another route. Another important one is that the eggs of certain fish species will stick to the legs of water birds, who then fly to other waters. Several UK species have this characteristic. Also, in the case of brown trout, I think the sea-going seatrout is actually considered the same species, so it's possible for seatrout to enter a lake isolated from others but with a river connecting it to the sea and then to take up fulltime residence as what we know as brown trout. I think the same can be said of N American Rainbows/steelheads, and less commonly Atlantic salmon.

Don't underestimate how far back humans have been tampering with things, either. For example, carp were introduced to UK waters from the continent as long ago as 1000 years. I think brown trout were introduced to S America several hundred years ago. I'm sure local populations of humans were moving fish between lakes for thousands of years prior to that.

More specifically regarding evolution, I think certain lakes in Africa that for various reasons are particularly isolated, and have not been subject to glaciation, have been used for research. Indeed, I also recall reading that within very large lakes its possible for one species of fish to evolve differentally in separate parts of the lake.

Water fowl travel between lakes, and even with an extremely low rate of a fish egg sticking to feet or feathers, you get transport between lakes. Remember that many water fowl would actively look for fish eggs, and when eating, a few eggs can get stuck between feathers. If a duck raids a stickleback's nest, it's going to be a bit messy, with fish eggs going everywhere.

If you want to estimate the rate at which this would happen, find or make a lake without fish. Count all the ducks, geese, gulls and so on that ever put their feet in water until you see the first fish of a species. You need to estimate how good you are at detecting fish, then go back to the likely time of first introduction. Look in your records how many water fowl visited until that moment, and you have a rough estimate how frequently eggs would need to stick to birds to explain the frequency and speed of introduction.

Birds are also likely to be what brought to isolated Pacific islands land snails that would not survive salt water exposure on driftwood.

You have identified an important area of biological research, biogeography and how new habitats are settled. There has been research on the subject, so if you want to know more, I'm sure you can find it.

This is interesting stuff. Now I have another word to search: biogeography.

Also, any lake without an outlet will eventually be unable to sustain life because of mineral loading of the waters. A fish can swim up an outlet.

at least you would be willing to admit you may be wrong*. it's more than most people who challenge the idea of evolution.




*i think this is an admirable trait and something that is severely lacking from society..

Same thing with islands - they are the topological equivalent of isolated lakes. Island biogeography is an interesting discipline - if the islands are truly isolated for long periods, then differences appear and speciation occurs.