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[trinityvixen]

Good article for those not up on their taxonomy.

I love disabusing human prejudice in the sciences. We're prone to giving so much attention to animals, and, within all of Animalia, mammals. The truth is that animals are so ridiculously outnumbered, species-wise, compared to bacteria. Hell, they can hardly compete in numbers with archaeobacteria.

I once saw this truly awesome graphic in a class where the phylums under the sub-domain Animalia were represented in size. There was a tiny kangaroo for the mammals and a beetle about thirty times the size of all the rest combined. One in five species of animal is a beetle, folks--not in terms of numbers of animals, but in terms of numbers of species. For every five animal species, one is a beetle. It just lets you know, then, how many out of five are insects. Now imagine how many orders of magnitude more bacteria species there are. Aiyah. Awesome.

Comments

[trinityvixen.livejournal.com]

Of course, isn't the underlying reason for the much greater variation in bacteria versus plants or animals just the fact that they've been around so much longer?

Some of it, yes. It definitely accounts for how there are more extinct species of bacteria than there have EVER been of animals. But there are other factors. You mentioned the ability to of plasmid (yes, they're real things, I use them all the time) DNA uptake. That, technically, would make a certain bacteria a "strain" not a "species" if the plasmid weren't integrated into the bacterial DNA (plasmids exist in the cytoplasm as separate, replicating strands). If it is integrated, you can make a better case for speciation.

Eukaryotes, on the other hand, are very difficult to mutate and change, and they have such specifically structured organelles and systems that it is very easy it destroy them if something is altered. The bacterium's lack of complexity saves it. Bacteria can live and even thrive with much of their DNA removed.