Thursday, February 16, 2012

A invenção da agricultura

Meet Dicty the amoeba – the world’s smallest farmer, no Not Exactly Rocket Science:

Meet the world’s smallest farmer – a “social amoeba” that seeds new land with bacteria, which it then eats. Just as human farmers carry seeds and livestock when they move to new areas, the amoeba can prepare for harsh conditions by bringing a ready food supply with it. It joins ants, termites and humans on the list of creatures that practice agriculture. (...)

Scientists pieced together Dicty’s life cycle decades ago, but it still carries surprises. Debra Brock from Rice University captured 35 wild amoebas from Virginia and Minnesota and found that a third of them carried bacteria in their slugs and spores. The bacteria hail from a number of different species, and half of these are found on Dicty’s menu. When the spores land in new locations, their bacterial cargo start to multiply, which provides the amoebae with food.

When Brock scattered spores in a sterile dish, she found that the “farmers” fared better. By seeding the dish with their bacterial cargo, they had a ready source of food. If the spores didn’t have any bacteria, the amoebae hatched to find a famine awaiting them. Very few completed their life cycle. Sterile soils may be rare in nature, but Brock found that the farmers kept their advantage when they landed in soil that had the wrong kind of bacteria. Dicty is a fussy eater, so it pays for it to carry around its preferred morsels.

This is a more passive style of farming than ants, termites or humans. Dicty doesn’t actually do anything to grow its bacteria, short of taking it to the right place. By contrast, ants and termites grow fungi by keeping it in just the right conditions, feeding it with leaves, and pruning away weed. Humans do the same for the crops that they farm.

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