Speciesization in a Test Tube

We can even see the origin of new, ecologically diverse bacterial species, all within a single laboratory flask. Paul Rainey and his colleagues at Oxford University placed a strain of the bacteria Pseudomonas fluorescens in a small vessel containing nutrient broth, and simply watched it. (It’s surprising but true that such a vessel actually contains diverse environments. Oxygen concentration, for example, is highest on the top and lowest on the bottom.) Within ten days—no more than a few hundred generations—the ancestral free-floating “smooth” bacterium had evolved into two additional forms occupying different parts of the beaker. One, called “wrinkly spreader,” formed a mat on top of the broth. The other, called “fuzzy spreader,” formed a carpet on the bottom. The smooth ancestral type persisted in the liquid environment in the middle. Each of the two new forms was genetically different from the ancestor, having evolved through mutation and natural selection to reproduce best in their respective environments. Here, then, is not only evolution but speciation occurring the lab: the ancestral form produced, and coexisted with, two ecologically different descendants, and in bacteria such forms are considered distinct species. Over a very short time, natural selection on Pseudomonas yielded a small-scale “adaptive radiation,” the equivalent of how animals or plants form species when they encounter new environments on an oceanic island.


Bacteria evolve into different species in order to adapt to the different environments at the bottom and top of a test tube.

Folksonomies: evolution experiment

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Evolution (0.983734): dbpedia | freebase | opencyc
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Natural selection (0.610013): dbpedia | freebase
Biology (0.512944): dbpedia | freebase | opencyc
DNA (0.496462): website | dbpedia | freebase | yago
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 Why Evolution Is True
Books, Brochures, and Chapters>Book:  Coyne , Jerry A. (January 22, 2009), Why Evolution Is True, Penguin (Non-Classics), Retrieved on 2011-09-15
Folksonomies: evolution evidence creationism