Swedish botanist Carl or Carolus Linnaeus is, by some measures, the most influential person ever to have lived. He is famous for devising new systems for naming and grouping all living organisms, as well as naming thousands of species. He studied medicine and science at the University of Lund and Uppsala University. At this time, botany was an important part of medical training, as doctors had to be familiar with many types of plant and their medicinal properties in order to treat their patients.
But memorising scientific plant names was extremely difficult — each one was known by a long description in Latin. One way to depict these relationships is via a diagram called a phylogenetic tree or tree of life. In these diagrams, groups of organisms are arranged by how closely related they are thought to be.
In early phylogenetic trees, the relatedness of organisms was inferred by their visible similarities, such as the presence or absence of hair or the number of limbs. Now, the analysis is more complicated. Today, phylogenic analyses include genetic, biochemical, and embryological comparisons, as will be discussed later in this chapter.
In , Ernst Haeckel, a German biologist, philosopher, and physician, proposed another kingdom, Protista, for unicellular organisms Figure 2. He later proposed a fourth kingdom, Monera, for unicellular organisms whose cells lack nuclei, like bacteria. Figure 2. He later added a fourth kingdom, Monera, for unicellular organisms lacking a nucleus.
Nearly years later, in , American ecologist Robert Whittaker — proposed adding another kingdom—Fungi—in his tree of life. Empire Prokaryota contained just the Kingdom Monera.
Figure 3 shows how the tree of life has changed over time. Note that viruses are not found in any of these trees. That is because they are not made up of cells and thus it is difficult to determine where they would fit into a tree of life.
Figure 3. This timeline shows how the shape of the tree of life has changed over the centuries. Even today, the taxonomy of living organisms is continually being reevaluated and refined with advances in technology. Antibiotic drugs are specifically designed to kill or inhibit the growth of bacteria. But after a couple of days on antibiotics, Cora shows no signs of improvement. Also, her CSF cultures came back from the lab negative. Viral meningitis is still a possibility. However, Cora now reports some troubling new symptoms.
She is starting to have difficulty walking. Her muscle stiffness has spread from her neck to the rest of her body, and her limbs sometimes jerk involuntarily. But the advent of molecular genetics in the late 20th century revealed other ways to organize phylogenetic trees. Genetic methods allow for a standardized way to compare all living organisms without relying on observable characteristics that can often be subjective. Modern taxonomy relies heavily on comparing the nucleic acids deoxyribonucleic acid [DNA] or ribonucleic acid [RNA] or proteins from different organisms.
The more similar the nucleic acids and proteins are between two organisms, the more closely related they are considered to be. Linnaeus set out alone on horseback from Uppsala the day before his 25th birthday, equipped with little more than a plant press, a gun, a hand lens and a change of clothes. His aim was not just to collect specimens from Sweden's land of the midnight sun but to learn how the "happy Lapps"—indigenous Sami people—and Swedish and Finnish homesteaders made use of them.
It was arguably the world's first ethnobotanical expedition. To stretch the limited funds he had been given by the Swedish Royal Society of Science to make the journey, Linnaeus adopted the local lifestyle, including eating reindeer tongues. He admired the Lapps' resourcefulness. They baked bread from fir bark, pine needles, dried fish, moss and seaweed. They had 18 ways of using milk, including "fresh boiled and coagulated with beer" and "mixed with sorrel leaves and preserved till winter in the stomach of a reindeer.
His diary is filled with a young man's ebullience. Charmed by the sight of bog rosemary in full bloom, its blossoms the color of "a fine female complexion," he thinks of Andromeda chained to her watery rock, and decides to give the plant genus that name.
On learning that Sami bachelors carry about pieces of sweet-smelling fungus as a kind of cologne- cum -aphrodisiac, he exclaims, "O whimsical Venus!
In other parts of the world you must be wooed with coffee and chocolate, preserves and sweets, wines and dainties, jewels and pearl As he traveled and collected—discovering and eventually naming over new species—his thoughts turned to the floristic differences between Lapland and the rest of Sweden, and to the benefits that would accrue if species could be swapped between the two regions.
But why stop at botanical rearrangement within the country, Linnaeus wondered; why not borrow from "God's endless larder" elsewhere in the world? Other nations had overseas colonies that supplied them with goods they couldn't produce at home; Sweden could go one better by cultivating the crops of the world within its own territory. Linnaeus believed that acclimatization, the process by which organisms become habituated to a new environment, could be the engine of economic growth for his "dearest Fatherland.
Back in Uppsala, fired by patriotic zeal and a naive confidence in the adaptability of nature, he became obsessed with the idea of cinnamon groves and tea plantations flourishing under a Baltic sun.
Unswerving in his belief that any plant could be "tamed" to withstand a more rigorous climate, he looked to a day when fashionable Europeans would wear Swedish silk, drink Swedish coffee and eat Swedish rice.
Ultimately, Linnaeus was mistaken in his view that plants are globally interchangeable—a conclusion he reluctantly came to accept after most of his horticultural transplants failed. A notable exception was rhubarb, a native of Asia, whose introduction to Sweden was an achievement he took pride in. Linnaeus was also wildly wrong about the number of living species.
He thought there might be around 40, all told; estimates today range from 10 million to million, most of which are microscopic. Many of his ideas now seem ludicrous. He believed epilepsy could be caused by washing one's hair, and leprosy caught by eating herring worms. He persisted in the archaic belief that swallows wintered at the bottom of lakes. Others were quaint: he devised a clock based on the opening and closing times of various flowers.
But many of his other views were surprisingly modern. Scientists are debating which species are most closely related and why. Currently in New Zealand, there are projects to sequence kiwi and tuatara DNA that may revolutionise the way we think about these species and their closest living relatives.
However, DNA technology is still expensive and time-consuming, so the first step in any classification continues to rely on a comparison of morphological features, similar to the process that Linnaeus undertook in the s. Your students can learn more about how the Linnaean classification system works with this activity, Insect mihi.
Classification is not a field that stays still and this means scientists and taxonomists sometimes have to reassess classifications. Learn more in Leon Perrie 's thought provoking blog, Why do scientific names change?
Learn more about the five kingdoms on the Biology Online website. Add to collection. Nature of science Improved technologies have altered our understanding of the world. Activity idea Your students can learn more about how the Linnaean classification system works with this activity, Insect mihi.
Find out more Classification is not a field that stays still and this means scientists and taxonomists sometimes have to reassess classifications.
Useful link Learn more about the five kingdoms on the Biology Online website. Go to full glossary Add 0 items to collection.
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