Background
What does a teacher need to know in order to teach this unit? Here are four areas of information to give you background knowledge: the legacy of Carl Linnaeus, classification, evolutionary theory up to 1800, and Darwin's concept of evolution and its effect.
Carl Linnaeus or Carl Von Linne, and Binomial Nomenclature
Carl Linnaeus (also known as Carl Von Linne) was a Swedish botanist who is credited with developing this first system to order and classify living things. He lived from 1707 to 1778, and his ideas were aligned with Creationism. As a boy, he enjoyed working in the garden with his father. He continually asked his father the names of plants, and forgot them as quickly. His irritated father told him he would be given no more names unless he remembered them. Perhaps this sparked his interest in naming plants that would be his life's work. 2 He began studying Latin at age seven, and apprenticed to a doctor at a young age. He was taught botany and medicine (the two subjects were considered to be practically one and the same), and that the sexual structure of plants is comparable to that of human beings.
By age 24, he had published four books on plants, and went in 1732 on an expedition to Lapland for five months to study and catalogue plants. He had a good friend named Pehr Artedi, who was an expert on fish, reptiles, and amphibians. The two worked together for seven years and developed a way of calling plants and animals: binomial (by two names) nomenclature (naming). Artedi drowned in an Amsterdam canal in 1735, and Linnaeus continued his work alone. Linnaeus did not invent the use of two names to describe plants. The Romans, for example, would have described two different kinds of wheat as triticum Africam, and triticum Alexandrinum. The naturalist John Ray also called plants by two, three, or four word names, which began with the genus and species, and then described the plant with a short phrase. Linnaeus simplified the names, often combining the vernacular name with the Latin name. The first name is genus (beginning with an upper case letter) and the second name is species (beginning with a lower case letter), although Linnaeus' full rank system included five levels: kingdom, class, order, genus, and species. The second name often incorporates the name of a person related to the species or the species' common name. Linnaeus often named plants after people. For example a Magnolia tree is named after the French botanist Pierre Magnol, whom he admired, and the genus Sigesbeckia, a small weed that grows in the mud was named after his main critic, Johann Siegesbeck. His system became generally adopted by botanists and zoologists in the second half of the 18 th century due to the comprehensive volumes that he published, which soon became indispensable to naturalists. His system of binomial names is still used today.
Classification
The Systema Natura, was published in 1735, using Latin, the language of science at that time. This book was very well received and he rose in fame and fortune quickly. Linnaeus' classification of plants relied primarily upon the sexual system of plants. He counted the number of stamens (the male organ) to determine the class, and the number of pistils (the female organ) to determine the order. Victorian botanists were outraged that he used sexual systems to classify plants, finding this revolting and disgusting, and wondering how ladies would ever be able to count the sexual parts of plants. However, this system ensured that botanists were talking about the same plant, and reduced confusion in classifying plants and animals, facilitating the study of botany and zoology. 3 In a similar way, Linnaeus developed a system to sort animals based upon the morphology of their structures, into different varieties. There have been a few changes to his categories, however, we still basically use the system that he introduced: Kingdom, Phylum, Class, Order, Family, Genus, and Specie. Here is an example of how a domestic dog would be listed using Scientific classification: Kingdom: Animalia, Phylum: Chordata, Class: Mammalia, Order: Carnivora, Family: Canidae, Genus: Canis, Species: C. lupus.
These categories are based on common physical characteristics, which move from general to specific and narrow. Most of the animals that First Grade students will research are vertebrates or Chordata. However, there are eight other phylum: Porifa, Cnidara, Platyhleminthes, and Nematoda – these four take their place closest down to the base of the tree of Animalia, or Animals, followed by a two more branches. On one branch are three more phyla: Mollusca (marine animals with shells), Arthropoda (animals with jointed legs and an exoskeleton, such as insects, arachnids, crustaceans, millipedes, centipedes), and Annelida (worms). Finally on the other branch there are two phyla: Echinoderm (animals such as a star fish) and Chordate (animals with a backbone, or Vertebrates). When small children think of animals, they are usually thinking of this last group, Vertebrates, which make up only five per cent of all animals. Vertebrates are then separated into the five classes: Mammalia (Mammals), Reptilia (Reptiles), Aves (Birds), Amphibia (Amphibians), and Ichthyetes (Fish). There are three kinds of Mammals: monotremes, marsupials, and placental mammals. Reptiles are ectothermal, and cannot regulate their inner body temperature. Birds have feathers and lay eggs. Amphibians have two different life stages. And finally there are three types of Fish: cartilaginous (like sharks), ray finned, and lobe finned.
Jean Baptiste Lamarck was responsible for organizing animals into the two major groups of vertebrates and invertebrates. He was the Chair of Botany at the Jardin du Roi in Paris, France from 1788 to 1793. After the French Revolution, this became the Musee National d'Histoire Naturelle (The National Natural History Museum). At age 49, he was given the role of 'Professor of Worms', which was a subject he knew little about. He spent the rest of his life categorizing invertebrates, a term that he coined. In 1803, he published on the groups Crustacea, Arachnida, Annelida, Insecta, and Mollusca, which he had named and defined.
Taxonomy is now the domain of an organization called the International Code of Zoological Nomenclature (ICZN), which names animals, and another called the International Code of Nomenclature for algae, fungi, and plants. The difference between classifying and taxonomy is that taxonomy is the science of identifying and naming species and organizing them into systems of classification. Taxonomy includes both classification and nomenclature. Classification deals with figuring out which species a specimen belongs in. Today, scientists look at DNA directly to sequence genetic code. 4
It is interesting to note that Linnaeus added humans to the "Great Chain of Being", a popular concept from the middle ages, which ordered minerals, plants, and animals in an ascending hierarchy, placing humans at the top of the staircase of life, in the group of animals called primates, which includes humans, other apes, and monkeys. He gave us our name Homo sapiens, or wise man. Linnaeus' system alluded to the relationship between the members of the same genus, but did not assert that organisms are related. Reaction to his works sparked interest in natural history during the 18 th century.
Evolutionary Theory (or the lack thereof) up to 1800
Until the publication of Darwin's On The Origin of Species, common belief among educated Westerners was that the account in Genesis, the first book of the Bible, was literally true, that the earth was thousands, and not billions of years old. It was believed that God created all species on Earth in the Garden of Eden, Adam named them, and they were in their original state, waiting to be discovered by explorers. God was thought of as a benevolent Creator, who had made all the plants and animals for human beings to enjoy. In Europe, as explorers returned to Europe with new specimens that were unknown, it became difficult to justify the diversity being encountered within the Biblical paradigm. Essays were being published (The Edinburgh Review) about the new life forms being discovered on oceanic islands, but they were published anonymously for fear of persecution for heresy. 5
In 1654, James Ussher, an Irish Archbishop, determined that the Earth was created in 4004 BC, by counting generations in the Bible. Up until late the 1800's, it was thought that the earth was thousands, and not billions, of years old. Likewise the idea that fossils represent extinct species had not yet been introduced. Fossilized shells found in high mountain areas and mines far from the sea were explained as having been brought there by Noah's flood. Fossils of animals that seemed to be extinct were thought to still be alive, undiscovered, somewhere on earth. However the works of Jean Baptiste Lamarck and Charles Lyell greatly influenced Darwin's wonderings about a different explanation. They put forth ideas about the Earth's dramatic past, along with Georges-Louis Leclerc (The Comte de Buffon), John Ray, James Hutton, William Smith, and the Baron George Cuvier. Jean Baptiste Lamarck posited that living things can change in reaction to their environments and acquire characteristics, and was a great influence on Charles Darwin. Charles Lyell, a British lawyer and geologist who published The Principles of Geology in three volumes between 1830 and 1833. Lyell estimated the age of the earth to be hundreds of millions of years old. His main idea in Volume 1 was his doctrine of Unifomitarianism -the assumption that what we see now here on Earth can describe the story of the Earth's past. Charles Darwin built upon Lyell's ideas, and became a close friend of Lyell in his later life. Lyell's work was the single greatest influence upon Darwin's thinking. It is unlikely that he could have put forth his theory of Evolution without it. Lyell remained a Creationist until late in his life.
Charles Darwin
Life from 1809-1831
Charles Darwin was a British naturalist who was born in 1809, the son of a physician, and the grandson of Erasmus Darwin, a physician and biologist. He loved collecting rocks and insects, and studying birds as a young boy. He enjoyed helping his older brother in conducting chemistry experiments in the tool house, and went in 1825 with the same brother to study medicine at Edinburgh University (in Scotland). The reluctant medical student began studying natural history, and was introduced to the ideas of Jean Baptiste Lamarck, whose Philosophie Zoologique (1809) stated that species had the ability to acquire characteristics in response to their environment, and pass those characteristics on to their offspring. Charles' Grandfather, Erasmus Darwin, who published Zoonomia: or the Laws of Organic Life in 1796, shared this view. Although Charles never met his grandfather, who died before he was born, ideas about evolution were discussed in Charles' free thinking family's home, and certainly influenced young Charles. He began to study Marine Biology, attending the Royal Society of Edinburgh, which met to discuss and debate Scientific Research. Charles then spent three years at Cambridge, ostensibly to study Theology; however, Darwin described these as wasted years. 6 He developed a friendship with Prof. Henslow, a geologist, and accompanied him on several outings to look for fossils in North Wales.
The Voyage of the Beagle 1831 to 1836
Professor Henslow recommended Darwin as a naturalist to the captain of the Beagle, a ship that was setting out on a mapping and exploring mission. Darwin described the voyage of the Beagle as the most important event in his life. In 1831, the Beagle set out on the journey that was meant to last two years. In fact it lasted five years. Darwin's own account of the trip implies that he began with a strong hunch about evolution, and it grew stronger with observations that led to the distillation of the principle of natural selection and the law of divergence. 7 Darwin recorded his experiences on this trip in his journal, The Voyage of HMS Beagle. The Beagle made its voyage down the eastern side of South America, around Tierra Del Fuego, and up the western side of South America, with an important stop at the Galapagos Islands. It also traveled to Tahiti, New Zealand, and Australia. Darwin made extensive observations of geology, plant life, and animals along the way, and collected specimens. Here are a few of his key findings: he discovered a fossil of a giant extinct armadillo-like animal (glyptodon) that shared the body armor and shape of extant armadillo species. Darwin described the phenomenon of species changing only moderately (usually becoming smaller) than their extinct prototypes, calling it a "law of the succession of types". This had also been described by Lyell, who had commented on finding extinct marsupials in caves of Australia. Darwin also noticed that as he travelled down the east side of South America he saw similar, or "closely allied animals replace one another in proceeding southwards" 8. The paleontological and geographic variation gave him evidence of the ability of species to change over time. Darwin wrote of "becoming a zealous disciple of Mr. Lyell's book", and proclaimed himself to be a uniformitarian. He described, in a letter to his sister (April 1835), collecting shells at an elevation of 12,000 feet in the Andes, and how he hopes they will "give an approximate age to these mountains." 9
Darwin is usually associated with the Galapagos Islands, an archipelago with many endemic species located 600 miles off the coast of South America near Ecuador. The islands are named for the Spanish word, tortoise, because of the giant tortoises which sailors found so tasty. The Beagle stopped here for five weeks, of which Darwin spent three on shore. The islands had been a stop for pirates and whalers, and only recently, on Charles Island, a small settlement of two or three hundred Ecuadoran people who were banished for different crimes had been established. The islands are about 50 or 60 miles from each other, some being lush and forested, others arid and barren of vegetation. The sea is very deep between them, so there is no evidence that the islands were ever united, but rather formed volcanically. Here, Darwin found evidence that species variation can occur within a geographic area. Darwin found finches with different beaks on each different island, perfectly adapted to their island's food sources. He believed that all the varieties of finches originally came from one variety of mainland finches. He also found tortoises from each island having distinctions. Some tortoises had shells that turned up in the front "like an English saddle", while others had rounder, blacker shells, and were tastier to eat. Darwin observed marine iguanas, unique to the Galapagos, that swim in the sea to feed on seaweed. Darwin also found plenty of variety among insects and plants of the Galapagos. Now, in addition to seeing how variation could occur over wide geographic areas of across great distances of time, was evidence that within the same geographic area, variation in isolation could occur.
The Long Delay 1836-1859
There was a twenty-three year delay between Darwin's return from his trip on the Beagle in 1836, to the publication in the year 1859. Both Erasmus Darwin (Charles' grandfather) and Jean Baptiste Lamarck had presented the heretical idea that species are derived from, and descend from, common ancestors, rather than being specially created. The work of Erasmus Darwin (Zoonomia in 1796), and Lamarck (Zoological Philosophy in 1809) had been met with a hostile reaction from the church, and Erasmus Darwin's publisher had been jailed. In the eyes of the Church, to discredit the Bible meant removing human beings from the center of the universe, and detaching man from God. During this time, Darwin refined his ideas and gathered more information to support his theories. He published his journal of the trip on the Beagle in 1839, which was well received and established him as a popular author. His friend Henslow, who had set him up with the trip, had shared some of his letters written from the Beagle with other biologists at the Philosophical Society of Cambridge, and Darwin found himself welcomed into the world of Scientists. In 1839 he married his cousin, Emma Wedgewood, and they started a family. He became a geologist alongside of Lyell, and studied Coral Reefs, publishing on that subject in 1842. At some point during his trip, Darwin had contracted a parasitic disease (probably Chagas' disease) that he struggled with for the rest of his life. Because he was so often confined to his home, he became a prolific letter writer, corresponding with other biologists, gardeners, gamekeepers, animal and plant breeders, and people he had met in different parts of the world. These letters have been great source of information. He also became an expert on barnacles, and spent eight years deeply involved in barnacle research.
On The Origin of Species
In 1844, Darwin finished his first draft of On The Origin of Species. He still didn't feel compelled to publish, but rather seemed content to continue his daily research. Ironically, after a long wait, Darwin rushed to finish his opus at the end of 1858. His friend and colleague, Alfred Russel Wallace, was simultaneously working on a similar theory, and had written to him for advice. Wallace and Darwin wrote a joint paper in June of 1858 entitled The Tendency of Species to form Varieties; and on the perpetuation of Varieties and Species by Means of Selection, which was presented, to the Linnaean Society. The paper did not get much attention, however Darwin hurriedly got his book published 18 months later in order to establish public claim. Darwin was the first to use empirical data, argument upon argument, and simple logic to prove his idea that the reason we see biodiversity was not because each species was individually created, as previously thought, but because each species are lineal descendants of other species. This is the idea that the fastest, strongest, or best able to withstand hardships and successfully reproduce, will be the species that we see before us.
Natural Selection
Darwin used the example of how man has domesticated wild plants by choosing the best ones to propagate, allowing for better quality fruits than one would find in the wild. Likewise, domesticated animals are bred to improve certain qualities. Darwin became very familiar with pigeon breeders, and learned how breeds are improved when breeders notice small differences among their animals. These same individual differences occur in nature. Flowers with the most attractive blossoms get more bee visits and have greater pollination. He noted that some plants and animals evolved together, such as the red clover and the 'humble-bees' corolla and proboscis that encouraged the maximum amount of pollen to get on the bees head during visits to the clover. These adaptations, or traits, that helps an organism to function and meet its needs, are evident in all animals and plants:
"How have all those exquisite adaptations of one part of the organization to another part and to the conditions of life and of one distinct organic being to another being been perfected? We see these beautiful co-adaptations most plainly in the woodpecker and mistletoe; and only a little less plainly in the humblest parasite which clings to the hairs of a quadruped or feathers of a bird; in the structure of the beetle which dives through the water; in the plumed seed which is wafted by the gentlest breeze; in short, we see beautiful adaptations everywhere and in every part of the organic world." 10
The Struggle for Existence
Upon returning home from his trip, Darwin read the work of Thomas Robert Malthus, an English scholar who wrote about the effect that the Industrial Revolution had upon human populations. He observed that two factors that work upon population growth are famine and disease. At some point, he wrote, "The power of population is indefinitely greater than the power in the earth to produce subsistence for man." 11 To Darwin, this meant that as a group of animals became more numerous, at some point the limit of resources available to those animals would put pressure on the group. Darwin stated, "It at once struck me that under these circumstances favorable variations would tend to be preserved, and unfavorable ones destroyed. The results of this would be the formation of new species. Here, then, I had at last got a theory by which to work." 12 Darwin noted many other issues that cause a group to struggle. Some animals have to endure very harsh climates. Their ability to live in very cold or very hot places determines their success (for example, the Emperor Penguin or the Desert Tortoise). Other species face the attacks of predators or the challenge of catching prey. Although a frog may lay hundreds of eggs, only one or two will survive to adulthood and breed. The ability to run the fastest, hide, or attack and catch enough prey determines their success. Still others compete with similar species struggling over the same district for food, or surviving drought or severe storms.
Inheritance
Darwin stated that the individuals with traits that helped them survive were most likely to survive and reproduce. In turn, the offspring of these animals would inherit those traits that had made their parents the fittest. The phrase 'survival of the fittest' came from Darwin's friend Herbert Spencer. He emphasized that a fit individual was one of the species that reproduced. Individuals with those traits that had handicapped them would be less likely to reach maturity, and would find it more difficult to find a mate and reproduce. As a result, those traits would slowly disappear form the population. Over many generations, the species would transform. Darwin called this process Natural Selection.
The Effect of the Origin
On The Origin of Species was published in 1859, and over 90 publications reviewed it. There was, as expected, a tremendous amount of hostile reaction to it from the Church. Anglican clergymen (11,000) made a declaration stating that the Bible must be read literally. Many scientists, however, received it with enthusiasm. There was a famous debate in June of 1860, between Henry Huxley, a biologist known as Darwin's bulldog for his defense of Darwin, and Bishop Wilberforce. Most believe Huxley to have won the debate, and within a decade, most educated people believed his theory of Evolution, and not Creationism, to be the reason why biodiversity occurs.
Charles Darwin continued his work, publishing The Descent of Man in 1871. Asa Gray spread his work to the United States, and Ernst Haeckel spread his work to Germany. Darwin died in 1882, and was buried in Westminster Abbey next to Lyell. In the United States, evolution teaching was challenged in 1925 during the Scopes trial. This led to the Butler Act, which banned the teaching of evolution. However, in 1967 the Butler Act was repealed, and in 1968, the U.S. Supreme Court prevented any State from banning evolutionary teaching to promote religion.
Darwin's ideas have influenced the fields of virology and bacteriology and how doctors use anti-viral and antibiotic drugs to fight infections, as they have to consider antibiotic resistance to drugs. Darwin's ideas have led to animal welfare laws, and the outlawing of research on primates, whereas before Darwin, animals were seen as having been created for man's pleasure and benefit. His ideas have changed the way we think about our natural world, and how we affect it.
Comments: