TYPES OF PLANTS KINGDOMS OR CLASSIFICATION
Biology: Scientists Reclassify Plants
into Three Separate Kingdoms
into Three Separate Kingdoms
Plants should
actually be classified as belonging to three distinct kingdoms rather than to
just one, according to the conclusions of a five-year project that involved 200
scientists from 12 countries.
actually be classified as belonging to three distinct kingdoms rather than to
just one, according to the conclusions of a five-year project that involved 200
scientists from 12 countries.
The conclusions were
presented on August 4, 1999, to the XVI International Botanical Congress in St.
Louis, Missouri. The analysis is widely considered the most comprehensive
outline of how plant life evolved. But scientists involved in constructing the
new outline noted that their findings were still preliminary and that the new
picture of plant evolution was likely to change with the collection of fresh
data.
presented on August 4, 1999, to the XVI International Botanical Congress in St.
Louis, Missouri. The analysis is widely considered the most comprehensive
outline of how plant life evolved. But scientists involved in constructing the
new outline noted that their findings were still preliminary and that the new
picture of plant evolution was likely to change with the collection of fresh
data.
According to the
research team, there are at least five major kingdoms, or branches, of
multicellular life: animals, fungi, green plants, red plants, and brown plants.
In the past, all known varieties of plants were typically grouped within a
single plant kingdom. Team leaders said their work also confirmed earlier
research suggesting that fungi—including mushrooms and yeast—belonged in a
separate kingdom.
research team, there are at least five major kingdoms, or branches, of
multicellular life: animals, fungi, green plants, red plants, and brown plants.
In the past, all known varieties of plants were typically grouped within a
single plant kingdom. Team leaders said their work also confirmed earlier
research suggesting that fungi—including mushrooms and yeast—belonged in a
separate kingdom.
Among the team's
major findings was that plants now growing on the land evolved from freshwater
plants. This challenges the long-accepted view that land plants originally
evolved from plants living in the sea. The team also traced all living land
plants to a common ancestor, a primitive type of green plant. In addition, the
researchers said they have identified the closest living relative of the
world's first flowering plant—a single species found only on the island of New
Caledonia in the South Pacific Ocean.
major findings was that plants now growing on the land evolved from freshwater
plants. This challenges the long-accepted view that land plants originally
evolved from plants living in the sea. The team also traced all living land
plants to a common ancestor, a primitive type of green plant. In addition, the
researchers said they have identified the closest living relative of the
world's first flowering plant—a single species found only on the island of New
Caledonia in the South Pacific Ocean.
The new analysis is
based largely on a classification approach known as cladistics. Unlike the
classical approach, in which organisms are grouped according to shared physical
characteristics, cladistics classifies organisms according to evolutionary
characteristics shared with a common ancestor. Using the fossil record, genetic
analysis, and other tools, cladists (scientists who specialize in
cladistics) create a family tree, or cladogram, to indicate when and where
different branches split off from the common ancestral line. Cladistics has
grown increasingly sophisticated in recent years, as advances in genomics,
a field that identifies evolutionary changes in the structure of genetic
material, have allowed researchers to quickly identify relationships among
living things.
based largely on a classification approach known as cladistics. Unlike the
classical approach, in which organisms are grouped according to shared physical
characteristics, cladistics classifies organisms according to evolutionary
characteristics shared with a common ancestor. Using the fossil record, genetic
analysis, and other tools, cladists (scientists who specialize in
cladistics) create a family tree, or cladogram, to indicate when and where
different branches split off from the common ancestral line. Cladistics has
grown increasingly sophisticated in recent years, as advances in genomics,
a field that identifies evolutionary changes in the structure of genetic
material, have allowed researchers to quickly identify relationships among
living things.
The researchers'
analysis showed that green plants, red plants, and brown plants evolved from
three different varieties of one-celled, plantlike organisms and should
therefore be grouped into separate kingdoms. Green plants comprise the largest
of the plant kingdoms and include shrubs, trees, grasses, ferns, mosses, and
flowering plants—about 500,000 species in all. Brown and red plants have
survived mostly as species of seaweed and microscopic algae known as diatoms.
analysis showed that green plants, red plants, and brown plants evolved from
three different varieties of one-celled, plantlike organisms and should
therefore be grouped into separate kingdoms. Green plants comprise the largest
of the plant kingdoms and include shrubs, trees, grasses, ferns, mosses, and
flowering plants—about 500,000 species in all. Brown and red plants have
survived mostly as species of seaweed and microscopic algae known as diatoms.
The team's work
points to a new understanding of how plant life emerged from an aquatic
environment and then exploded over the Earth's lands. Rather than invade the
land directly from the sea, where all plantlike organisms first evolved,
single-celled green plants first migrated to fresh water, where they developed
into multicellular organisms. To survive on land, green plants had to adapt,
developing new ways to remain moist and to reproduce. The researchers said
their evidence suggested these adaptations occurred more than 450 million years
ago.
points to a new understanding of how plant life emerged from an aquatic
environment and then exploded over the Earth's lands. Rather than invade the
land directly from the sea, where all plantlike organisms first evolved,
single-celled green plants first migrated to fresh water, where they developed
into multicellular organisms. To survive on land, green plants had to adapt,
developing new ways to remain moist and to reproduce. The researchers said
their evidence suggested these adaptations occurred more than 450 million years
ago.
Brent Mishler, a
biologist from the University of California at Berkeley and one of the team
leaders, noted that green plants had likely invaded the land at many different
times. However, the team's analysis suggested that only one plant lineage
survived and eventually diversified into all known land plants. This finding
challenges a common view among biologists that land plants evolved from several
distinct ancestors, including for example one for mosses and another for
flowering plants. The new work “indicates there's an Eve, a common ancestor, in
the primordial soup of green plants,” Mishler said. The team's data indicated
that the common ancestor was probably closely related to tiny green plants
known as coleochaetes, which still live in some of the world's pristine fresh
waters.
biologist from the University of California at Berkeley and one of the team
leaders, noted that green plants had likely invaded the land at many different
times. However, the team's analysis suggested that only one plant lineage
survived and eventually diversified into all known land plants. This finding
challenges a common view among biologists that land plants evolved from several
distinct ancestors, including for example one for mosses and another for
flowering plants. The new work “indicates there's an Eve, a common ancestor, in
the primordial soup of green plants,” Mishler said. The team's data indicated
that the common ancestor was probably closely related to tiny green plants
known as coleochaetes, which still live in some of the world's pristine fresh
waters.
The study also shed
light on the evolution of flowering plants, which first developed about 130
million years ago, team leaders said. Previous research suggested that
magnolias, or possibly water lilies, which have simple unspecialized flowers,
were the most primitive flowering plants still alive. The researchers, however,
identified a species called Amborella, which grows only in New Caledonia
and produces small, cream-colored flowers, as closest to the earliest flowering
plants.
light on the evolution of flowering plants, which first developed about 130
million years ago, team leaders said. Previous research suggested that
magnolias, or possibly water lilies, which have simple unspecialized flowers,
were the most primitive flowering plants still alive. The researchers, however,
identified a species called Amborella, which grows only in New Caledonia
and produces small, cream-colored flowers, as closest to the earliest flowering
plants.
Scientists said the
new classifications were important for understanding how plants evolved and
could also have practical benefits. Researchers searching for plants with
medicinal value, for example, might more easily identify close relatives of
plants now used medicinally, experts said. Other experts noted that knowledge
about where plants fit on the evolutionary tree could help weed-control
specialists devise more effective attacks against invasive plant species by
employing techniques that have proved effective against close relatives of the
pests.
new classifications were important for understanding how plants evolved and
could also have practical benefits. Researchers searching for plants with
medicinal value, for example, might more easily identify close relatives of
plants now used medicinally, experts said. Other experts noted that knowledge
about where plants fit on the evolutionary tree could help weed-control
specialists devise more effective attacks against invasive plant species by
employing techniques that have proved effective against close relatives of the
pests.
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