Encyclopedia of Evolution.pdf - Online Reading Center

• Orders that evolved most recently from a common ancestor,
and are therefore most similar to one another, are
members of the same class. Carnivores, along with all other
mammals, are members of the Class Mammalia. The orders
within the mammal class share common features such as
the production of hair and milk.
• Classes of animals or protists that evolved most recently
from a common ancestor, and are therefore most similar
to one another, are members of the same phylum (plural
phyla). In plants, fungi, and bacteria, this category has traditionally
been called a division. Mammals, along with all
other vertebrates (which possess a backbone), and those
other animals that have a flexible rod instead of a backbone,
are members of the Phylum Chordata.
• Phyla or classes of organisms that evolved most recently
from a common ancestor, and are therefore most similar
to one another, are members of the same kingdom. Most
biologists recognize five kingdoms of organisms.
In recent years, biologists have clustered kingdoms into
three domains. Two of the domains, often placed into the
Kingdom Monera, consist of single-celled organisms commonly
called bacteria:
• The archaebacteria (Domain Archaea) live in environments
such as deep ocean volcanic vents and salt slush that, while
they seem extremely inhospitable to humans, are similar to
the conditions found on the early Earth (see archaebacteria).
• The eubacteria are mostly the bacteria that live in soils and
water, and on or in larger organisms, on the Earth’s surface.
Some of them are green and make food energy from
sunlight by photosynthesis (see bacteria, evolution of).
The other three kingdoms consist of organisms that
either are, or are constructed from, a more complex form of
cell called eukaryotic and make up the Domain Eucarya (see
eukaryotes, evolution of):
• The protists are either single-celled or, if multicellular, are
not organized into fully integrated bodies.
• The fungi secrete digestive enzymes, then absorb the digested
food molecules individually from the environment.
• Plants make food from small molecules in the environment,
using energy from the Sun.
• Animals consume food as particles or chunks rather than
as individual molecules.
The protists do not all have a common ancestor that differs
from the common ancestor of fungi, plants, and animals;
therefore it is not a monophyletic group. Many biologists no
longer recognize Kingdom Protista as a formal category.
Early in the 20th century, some biologists applied the
Linnaean system at least roughly to communities, particularly
of the plants that dominated the landscape. Therefore,
to ecologists such as Frederick Clements, a forest of pines
(genus Pinus) was quite literally a Pinetum, and an oak forest
(genus Quercus) was a Quercetum. By the middle of the
20th century, however, biologists realized that each species of
organism had its own geographical range and set of habitat
Linnaeus, Carolus
preferences. A pine forest was not a coherent entity but rather
a collection of interacting species that happened to be in the
same place.
Further Reading
Kastner, Joseph. “An Adam and his apostle.” Chap. 2 in A Species of
Eternity. New York: Dutton, 1977.
Linnaeus, Carolus (1707–1778) Swedish Botanist Carolus
Linnaeus was the Swedish botanist who invented modern
taxonomic classification using Latin names (see Linnaean
system); he changed his own name, Karl Linné, into Latin.
Linné was born May 23, 1707. Like many other important
intellectuals in world history, Linnaeus showed little
promise as a student. His father apprenticed him to a cobbler,
which inspired Karl to go back to school and improve his
grades. He studied medicine, but his passion, starting in his
twenties, was to catalog all the known species of organisms.
Linnaeus was passionate about two other things as well.
First, he was passionate about his own greatness. He wanted
Princeps Botanicorum (prince of botanists) on his tombstone
and considered his method of classification to be “the greatest
achievement in the realm of science.” Second, he was
passionate about sex. He used a sexual system, based upon
anthers and pistils, to classify plants. But he went further.
His terms for the anatomy of mollusks included vulva, labia,
pubes, anus, hymen, even though the structures he described
had no relation to the corresponding parts of human anatomy.
Among the names he gave plants were Clitoria, Fornicata,
and Vulva. His descriptions of plant reproduction were
very florid. He described the parts of the flower, correctly, as
sexual organs but went further: “The flowers’ leaves serve as
a bridal bed … the bridegroom with his bride might there celebrate
their nuptials … then it is time for the bridegroom to
embrace his beloved bride and surrender himself to her.” Predictably,
some scholars disliked Linnaeus’s sexual classification
system. A professor in St. Petersburg, Johann Siegesbeck,
wrote that God would not have created the natural world
based on this “loathsome harlotry.” Linnaeus’s response was
to name a small, ugly weed Siegesbeckia (now Sigesbeckia) in
his honor. In his personal life, Linnaeus was very conservative,
despite his florid writings.
The order that Linnaeus brought into biology by this
system, however, inspired nearly all scientists. In particular, a
number of young men were his disciples and explored all over
the world, at great personal risk, to find new species of plants
to classify with the Linnaean system. Peter Kalm explored
Canada during the height of the tensions between France and
England; Frederik Hasselquist explored Egypt; Peter Osbeck
went to China; Pehr Löfling went to Spain; and Lars Montin
went to Lapland, all spending their own fortunes to collect
plants and send them back to Linnaeus. Though not a disciple
of Linnaeus, botanist John Bartram went into the wilderness
of the American southeast looking for plants and was
one of the first white visitors to the Cherokee tribe.
Another reason that Linnaeus’s system caused a flurry
of botanical exploration is that it allowed naturalists to
name plants after themselves or other naturalists whom they