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- Scientists have discovered that every plant species alive
on land today shares a single common ancestor, at least 450 million years
old.
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- The finding, by the 200 scientists of the Green Plant
Phylogeny Research Co-ordination Group, was disclosed at the 1999 meeting
of the International Botanical Congress in St Louis, Missouri, US.
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- The group, drawn from 12 countries, has spent five years
reconstructing the evolutionary relationships among all of the Earth's
green plants.
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- It says it has now developed the most complete "tree
of life" of any group of living things.
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- Blurring the boundaries
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- One team member is Brent Mishler, professor of integrative
biology at the University of California, Berkeley.
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- He said: "Better understanding of this 'tree of
life' will allow scientists to better predict the biological properties
of plants".
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- The team has clarified the plant "kingdoms"
and their relationships to animals.
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- They say there are five main trunks, or lineages, of
complex, "nucleated" organisms on the Earth's genealogical tree,
four of them classified as plants.
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- These are the green plants, the red ones (mostly seaweeds),
the brown plants, and the fungi, which themselves revealed a surprise.
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- Professor Mishler said: "We can't really think of
life on Earth in terms of only the 'animal kingdom' and the 'plant kingdom'
any more".
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- "The fungi are more related to animals than to plants
meaning that the mushrooms you eat are more related to you than to the
tree on which they are growing."
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- The original seed
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- The group also says that the green conquest of the land
was not led by seawater plants, but by freshwater ones, a reversal of traditional
scientific understanding.
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- And they say that only one plant was responsible for
the wealth of species alive today.
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- "Plants came out onto land probably many times,
but only one lineage actually made it", said Professor Mishler.
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- "This indicates there's an Eve - a common ancestor
- in the primordial soup of green plants."
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- The group's research shows as well that all the plants
and animals together form only a small part of the mass of living things.
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- The rest of it consists of mostly single-celled and poorly-known
organisms.
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- The researchers think the impact of this finding could
parallel the discovery centuries ago that the Sun is merely one star in
the whole universe.
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- They say their findings could shatter preconceptions
about life on Earth by showing that all the familiar biodiversity (including
human life) represents only one small twig on the tree of life.
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- Scientists have identified about 1.4 million species
of organisms. Estimates of the numbers still to be found range from 10
m to more than 100 m.
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