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Evolution History Evolution Part I: Who was Darwin? The story begins here Europe United Kingdom Shropshire county Incountry the town Shrewsbury InInthe of of England livedname this famous naturalist whose was Charles Darwin Age 65 Charles Darwin 1809 - 1882 This was his home and his garden Darwin would spend much time walking in his garden thinking about his discoveries and ideas. This was his glasshouse and his study Darwin spent a lot of time in his glasshouse and study examining various plants and animals and developing his theory of natural selection. Evolution History Evolution Part II: Darwin finds his niche. As a young man, Darwin started medical studies at Edinburgh’s famous medical school, but switched over to a course in scientific inquiry, becoming a naturalist instead. Darwin’s Occupation A naturalist is a person who studies past and present plant and animal life. Naturalists spend a lot of time collecting and classifying plants and animals. Like most naturalists, Darwin used Linnaeus’ Hierarchy of Taxononmic Levels to classify organisms. Carolus Linnaeus 1707 - 1778 Domain Eukarya Kingdom Animal Phylum Chordata Class Order Mammalia Family Canidae Genus Canis Species Canis lupus Carnivora Darwin on Classifying Darwin spent eight years in his study looking through a microscope at barnacles he collected from around the world What’s a barnacle you ask? Barnacle Structure The classic barnacle is an animal with the body plan of a volcano — a cone with a crater at the top. Barnacles live in water and colonize rocks, docks, and ships’ hulls, which cause the ships to slow down. Barnacle Life Every day when the tide rolls in, each barnacle pokes out of its crater a long foot like a feather duster and gathers food. When the tide goes out, each barnacle pulls in the feather duster and clamps its crater closed with an operculum—a shelly lid. “Barnacle Bill” Darwin found so much variation in barnacle structure and function that he had great difficulty classifying them. Before Darwin’s time, most people believed that all life suddenly appeared in its present form, (Special Creation); life was immutable (unchanging); the Earth was less than 10,000 years old. Some individuals however thought the earth was much older Georges Buffon James Hutton 1707 - 1788 1726 - 1797 The earth appears to be formed by slow action on natural causes. Some proposed that evolution occurred, but lacked convincing evidence for the driving mechanism. Inheritance of Acquired Characters Came up with The behavior of the individual determines the character that its offspring inherit. Jean Babtiste Lamarck 1744 - 1829 But example, that would involveon For passing modifying thebyDNA of longer necks stretching specific order for food genes seems in reasonable. for it to be inherited. We know Lamarck’s Inheritance of Acquired Characters doesn’t work because Seeds from trained When the tails dogs are and children of of body bonzai always cut off,trees the builders are“docked” not born look is produce offspring never inherited bythat their looking like Arnold grow to normal size. puppies. Schwartznegger Evolution History Evolution Part III: Darwin sets sail on the HMS Beagle. Darwin goes sailing In 1831 Charles Darwin, a 22 year-old college graduate set sail as Captain’s companion on the HMS Beagle for a voyage around the world. The main mission of the voyage was to chart poorly known stretches of the South American coastline for the British Navy. Darwin goes sailing Darwin’s main interest was to study the geology, plants, and animals encountered on the voyage. It was a tour that would greatly affect Darwin’s thinking and eventually the thinking of others. Darwin sees the world The map below shows the route the ship followed. Darwin’s Observations Darwin spent most of his time on shore while the ship’s crew was busy surveying. There, he observed and collected thousands of specimens of South American plants and animals from diverse environments. Darwin’s Observations He studied organisms and their adaptations from places as different as -the Brazilian jungle -the grasslands of the pampas -and the frigid lands near Antarctica. Darwin’s Observations Throughout the voyage and the rest of his life, Darwin maintained extensive journals of his observations, studies, and thoughts. These journals provide a window into Darwin’s thinking. Darwin’s mindset Before the voyage Darwin felt that the concept of fixed or unchanging species best described nature. During the voyage, he began questioning this concept. Sometime after he returned to England, Darwin became convinced that species change as they adapt to their changing environments. Fixed species Of a South American flavor Darwin noticed on his voyage that the South American plants and animals were quite different from the species of Europe. Common Sloth 6 kg Even the fossils Darwin found were uniquely South American. Some of the fossils were gigantic versions of the modern animals. Extinct Giant Sloth 3000 kg The Galapagos Archipelago His observations supported the idea that species living in South America today were descended from ancestral species on that continent. For example, The camelids of South America were believed to have descended from the long extinct camelid Poebrotherium wilsoni. The Galapagos Archipelago Darwin was also intrigued by life on islands such as the Galapagos. The Galapagos are a chain of relatively young volcanic islands about 900 km off the western coast of South America. Life on the Galapagos Darwin observed that the islands had many unique organisms. For example, Galapagos iguanas are unique because they swim in the ocean to feed on algae. Life on the Galapagos He observed that even the individual islands in the chain had some different species of plants and animals from one another. For example, Galapagos is famous for these unique, long-necked giant land tortoises whose shell patterns differ from island to island. Life on the Galapagos Darwin inferred from these observations that mainland species had changed after they colonized the islands and adapted to their various new environments. Case in point: All South American cormorant species can fly, but the Galapagos cormorant is flightless. Galapagos S. America Evolution History Evolution Part IV: Darwin begins to change his world view. Catching up on some reading During the Beagle’s long sails between ports, Darwin managed to do a lot of reading. The writings of the geologist Charles Lyell had a particular influence on Darwin. Lyle proposed that gradual and observable geologic processes such as erosion could explain the physical features of today’s Earth. Charles Lyell 1797 - 1875 Erosion and Earthquakes For instance, the gradual erosion of a riverbed over thousands or millions of years can result in a deep, river-carved canyon. A mighty mountain range can be thrust up centimeter by centimeter by earthquakes occurring over millions of years. All that was required for an understanding of these changes was an Earth far older than previously thought. Rising land Darwin personally experienced an earthquake while doing field studies in the Andes Mountains of Chile. In a harbor, he observed a block of land that had been underwater move upward above the water level as a result of the quake. Seashells on high He also collected fossils of ocean organisms high in the Andes. Applying Lyell’s ideas, Darwin reasoned that earthquakes gradually lifted the rock bearing those marine fossils from the sea floor. Drawing conclusions The geologic evidence presented by Lyell and others pointed to two conclusions. 1. The slow processes of mountain building and erosion suggested an Earth that must be very old. 2. The slow and gradual processes occurring over vast spans of time could cause enormous change on Earth. Darwin would eventually apply this idea of gradual change to the evolution of Earth’s life forms. Darwin’s Collection When Darwin and the Beagle returned to England after five years, he analyzed his collection and became convinced that Earth was ancient and species can change through time. The evolution of the horse is an example of how species can change over time. Eohippus Front foot = 4 toes Hind foot = 3 toes Darwin learned there were larger and smaller versions of animals living today that lived in the past. Selective Breeding Darwin then visited many farms and learned how farmers used selective breeding to bring about new varieties or species of plants, like those that come from a common wild mustard. Selective Breeding Darwin also learned how farmers used selective breeding to produce new varieties of dog, sheep, pig, horse and cattle. Darwin wondered if nature, like a farmer, could cause a selective breeding-like effect too. Selective Breeding Of course, there are some things that selective breeding and evolutionary changes cannot make. Pigeon Fancier Darwin tried his hand as a pigeon fancier. He was amazed to occasionally find that when he crossed purebred pigeons (like white fantails) he would occasionally get distinct rock pigeon markings in the F2 generation. x Darwin believed that despite the great differences between breeds, all pigeons were descended from the rock pigeon, or common pigeon. Common pigeon Pigeon Fancier Darwin also noted that domestic “fancy” pigeons, when released as breeding pairs into the wild, do not fair well and produce no successful future generations. Darwin inferred that the rock pigeon is successful in the wild because it adapts well to environmental demands. Evolution History Evolution Part V: Darwin develops his theory of natural selection. Population Studies In 1838, as Darwin continued to think about the question of how species change, he read an essay on human populations written a few decades earlier by Thomas Malthus. Thomas Malthus 1766 - 1834 Feast and Famine Malthus contended that much of human suffering, such as disease, famine and homelessness, was due to the human population’s potential to grow. That is, populations can grow much faster than the rate at which supplies of food and other resources can be produced. Struggle for existence Darwin recognized that Malthus’ ideas applied to all species. Numbers are kept in check by disease and the fight for space. Some die from a lack of water. Some die from lack of food. Struggle for existence Some die when they end up as someone else’s food. The production of more individuals than the environment can support leads to a struggle for existence. Struggle for existence To prove his point, Darwin counted the seeds from a single orchid plant. There were 24,080 seeds. That was 24,078 more offspring than were needed to replace the two parents. If each of these seeds grew into a plant and if all of these plants had 24,080 seeds, the whole world would be knee-deep in orchids. Struggle for existence But this is not the case. Some seeds are eaten by bugs. Some land on poor soil. Seedlings become sick or are crowded out by other plants. These are the losers in the struggle for existence. Natural Selection This concept helped Darwin to propose a mechanism of evolutionary change. He called it: NATURAL SELECTION Putting it all together In 1844, Darwin wrote a 200 page essay that outlined his idea, but he didn’t release it to the public. He told only a few of his closest colleagues about his theory, who encouraged him to publish his work before someone else came to the same conclusions. Darwin’s “Bulldog” Thomas Huxley 1825 - 1895 Another source In 1858, another British naturalist, Alfred Wallace, presented similar evidence and inferences. Within a month, Darwin and Wallace submitted joint papers to the public. Alfred Wallace 1823 - 1913 Evolution History A year later, Darwin published his book, The Origin of Species. “It is not the strongest of the species that survive, nor the most intelligent, but the one most responsive to change.” Charles Darwin Darwin’s main points 1. Decent with modification Species of organisms living on Earth today descended from ancestral species. These descendents spread into various habitats over millions of years. In these habitats, they accumulated different modifications, or adaptations, to diverse ways of life. Darwin’s main points 2. Natural Selection The process by which individuals with inherited characteristics well-suited to the environment leave more offspring on average than do other individuals. Evolution Timeline