Last week we mentioned Swedish botanist Carl Linnaeus’
role in crafting the binomial system of nomenclature, giving every plant a two-word
scientific name. In 1753 he published the results of his attempt to classify all known
plants in his monumental work Species Plantarum. Linnaeus based his classification
on various plant characteristics, usually focusing on the plant’s reproductive
structures. He grouped plants according to the knowledge available at the time—freely
admitting that his system was not comprehensive and would certainly be modified as more
knowledge was acquired. The general thinking during this time period was that every
individual plant and animal species had been created independently, and that individual
species were immutable—incapable of changing their form. As a result, any perceived
relationships between plants were based on appearance, not on historical or biological
connection.About 50 years after the publication of
Linnaeus’ work, French biologist Jean Baptiste de Lamarck put forward the first
theory of evolution. He suggested that certain features of animals evolved based on the
use—or disuse—of these parts. For example, a giraffe has a long neck because it
uses it so much. His theory received relatively little attention and support.
Fifty years later—about 100 years after the
publication of Linnaeus’ work—Charles Darwin challenged the still popular
theories of special creation with the publication of his revolutionary work On the
Origin of Species. In this manuscript, published in 1859, Darwin postulated that
individual species were the result of the process he termed natural selection—a process by which the
healthiest, strongest, and most well-adapted organisms flourished and went on to
reproduce.
Darwin further theorized that the diversity of species
could be attributed to the adaptations of organisms to environmental factors. These
adaptations are based on mutations, which are
random genetic changes that are passed on to offspring. Some mutations cause harm to the
organism; other mutations result in changes that are beneficial to the survival of the
organism in that particular environment. Organisms with these novel features outcompete
other species members, or survive where others perish. Over time, the surviving organisms
reproduce and perpetuate these new characteristics.
Keep in mind that evolution isn’t over—it
continues, but usually at a very slow pace. Perhaps the best example of evolution and
adaptation in our everyday lives occurs in the fields of medicine and pest management.
Occasionally, news of penicillin-resistant strains of bacteria or pesticide-resistant
insects makes the headlines. Small organisms with short life cycles are usually the
quickest to adapt to environmental change, because with each generation comes the
opportunity for genetic mutations that may lead to increased ability to withstand
stresses—including antibiotics and pesticides.
With this background information in mind, let’s
survey some of the ways plants have evolved to fill their basic needs and protect
themselves from predators.
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What a mouthful!
The full title of Darwin’s famous treatise is On the Origin
of Species by Means of Natural Selection, or the Preservation of Favoured Races in the
Struggle for Life.
Also, to give credit where it’s due, a young naturalist- explorer named
Alfred Russel Wallace proposed his own ideas on evolution by natural selection around the
same time as Darwin. |
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