The first tentative moves that got life out of the water and onto the land eons ago were apparently made by slimy green algae, scientists say, and coming ashore wasn't easy.
According to paleobotanist Russell Chapman of Louisiana State University, the first algae that managed to gain residence on terra firmafinally kick-starting the evolution of land plantsmust have come out of fresh water, not the sea.
And, Chapman said, even though four distinct types of algae managed to come ashore, only one of them evolved enough complexity to eventually cover the land with vegetation, what we now call trees, shrubs, flowers, and grass. Nonetheless, all four species of pioneering algae can still be found on land, he said.
The ancient history of land plants is becoming evident because of recent advances in techniques for genetic analysis. It's now possible to look at individual genes in algal cells and higher plants and calculate their similarity. Clues to the history of such organisms lie within the chemical "spelling"the sequence similarityof the organisms' genes. The closer they resemble each other, the closer they are related.
"The evolutionary history of various genes can be studied within the lineage of green algae," Chapman said, and that is what offers vital clues to how the algal genes eventually evolved to produce plants. Today's green plants are enormously varied, from the giant redwood trees to the tiniest weedseverything that blooms, including our crops.
All Plants Rose From Single Type of Algae
Chapman was speaking earlier this year during a symposium on the genetics and evolution of green plants at the annual meeting of the American Association for the Advancement of Science in San Francisco. He and several colleagues made it clear that today's multicellular plants, such as corn, cabbages and all the other greenery, arose from a single type of algae.
As noted by plant geneticist Brent Mishler of the University of California at Berkeley, the genetic evidence now being uncovered shows that "the multicellular land plants are all of one lineage. The fossil evidence suggests that others (types of algae) tried," but they failed to evolve the needed complexity. In other words, the three other algae that managed to wade ashore didn't evolve beyond the single-cell stage, so they remain what they were, algae.
The discoveries and the ideas of how land plants arose "reminds people of our humble origins," Chapman added. "This reminds people of how important algae are in general, since without that one escape from water and subsequent evolution, the half million species of plants that are so important to life on Earth might not exist. There would be no crops, no flowers, no fibers or foods. Also no us, of course."
(C) 2001 Charleston Daily Mail