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10.1: Early Ideas About Evolution • Objectives: Examine early ideas about evolution. • Identify three geological theories that influenced scientific debate over evolution. • Warm Up: Have you ever heard the expression, “survival of fittest”? What does it suggest to you? With evolution, what is it that survives? • Words to Know: Evolution, Species, Fossil, Catastrophism, Gradualism, Uniformitarianism. Early Scientists Proposed Ideas about Evolution • Evolution is the process of biological change by which descendants come to differ from their ancestors. • The concept had been discussed for more than 100 years before Darwin proposed his theory. Carolus Linnaeus (1700’s) • Swedish botanist. • Developed a classification system for all types of organisms known at the time. • Did not believe that organisms were fixed and did not change. • He proposed that they could change through hybridization. – A Species is a group of organisms so similar to one another that they can reproduce and have fertile offspring. Georges Louis Leclerc de Buffon (1700’s) • French naturalist in the 1700’s. • He proposed that species shared ancestors instead of arising separately. • He also suggested that the Earth was much older than the 6,000 years though by most. Erasmus Darwin (1700’s) • Charles Darwin’s grandfather. • Respected English doctor and poet. • Proposed all organisms evolved from a common ancestor and that more-complex forms of life arose from simpler forms of life. Jean-Baptiste Lamarck (1800’s) • • • • • • French Naturalist (1809) Proposed that all organisms evolved toward perfection and complexity. Proposed changes in an environment caused an organism’s behavior to change, leading to greater use or disuse of a structure or organ. The structure would become larger or smaller as a result. The organism could then pass these changes on to its offspring. Called the Inheritance of Acquired characteristics. • • • Ex: Giraffes had short necks They wanted to reach the leaves in the trees they stretched their necks long enough to reach the leaves over time their necks stayed long they passed these traits onto their offspring. HE WAS WRONG!!! What common ideas about organisms did these scientists share? Theories of Geologic Change Set the Stage for Darwin’s Theory The early common view was that the Earth was about 6000 years old, and that neither the Earth or the species living on it had changed in that time. Georges Cuvier (1800’s) • Believed species could become extinct. • Fossils are traces of organisms that existed in the past. • He found that fossils in deeper layers of rock looked much different from those in the top layers. • He explained is observations with the theory of Catastrophism. • Catastrophism states that natural disasters such as floods and volcanic eruptions have happened often during Earth’s long history. • These event shape landforms and caused species to become extinct. James Hutton (1700’s) • Scottish Geologist. • Proposed the idea of Gradualism which states that landforms resulted from slow changes over a long period of time. • Gradualism is a major component of evolutionary theory today. Charles Lyell (1800’s) • Published Principles of Geography in which he expanded on Hutton’s theory of gradualism into a theory of Uniformitarianism. • Uniformitarianism states that the geologic processes that shape Earth are uniform through time. • This soon replaced catastrophism as the favored theory of geologic change. • What important concepts about Earth did Hutton and Lyell agree upon? Mining for Black Opal in the Desert that used to be a Forest. 10.2: Darwin’s Observations • Objectives: Describe how Darwin arrived at his idea about species variation. • Recognize how Darwin’s discoveries supported Lyell’s ancient-Earth theory. • Warm Up: Thinking in terms of genetics, what is it about a cluster of islands that makes it a good laboratory for studying variation? What is it that the islands keep separate? • Words to Know: The Origin of Species, Variation, Adaptation Charles Darwin- the “Father of Evolution” • • He went on a voyage from 1831 – 1836 on the H.M.S. Beagle as the ships naturalist. The voyage went around the world and made a very important stop on the Galapagos Islands (a group of small islands off the west coast of South America). It was here that Darwin collected samples and observed the characteristics of many animals and plants varied noticeably among the different islands. Darwin began assembling his ideas upon his return from the voyage. However, he waited over twenty years (1859) before publishing his book On the Origin of Species. Because he was both stunned and disturbed by what he had observed/discovered as it challenged the fundamental scientific beliefs of that time (not to mention religious beliefs). Wallace, another scientist also had similar ideas. Darwin Observed Differences Among Island Species • Darwin was struck by the variation in traits he observed on his travels. • Variation is the difference in the physical traits of an individual from those of other individuals in the group to which it belong. • Ex: Different breeds of dogs. • Darwin noted that the species found on one island looked different from those on nearby islands and that many of the species looked different from those on the mainland. • The most notable differences he discovered were on the Galapagos islands, an island chain off the coast of Ecuador. Darwin Observed Differences Among Island Species • Some difference seemed well suited to the animals’ environments and diets. • Ex: Saddle-back Tortoises, which have long necks and legs, lived in areas with a lot of tall plants. • Domed tortoises, with their shorter neck and legs, lived in wet areas rich with mosses and short plants. Darwin Observed Differences Among Island Species • Ex: He noticed finches with strong, thick beaks lived in areas with a lot of large, hardshelled nuts,while those species of • finch with more delicate beaks were found where insects or fruit were widely available. • What he noticed was adaptations. • An Adaptation is a feature that allows an organism to better survive in its environment. • Adaptations can lead to genetic change in a population over time. • What adaptations did Darwin see in the finches of the Galapagos islands? Darwin Observed Fossil and Geologic Evidence Supporting an Ancient Earth. • Darwin found fossil evidence of species changing over time. • He found large fossils in Argentina that looked like a larger version of current animals. • He concluded that it must have taken a large amount of time in order for those changes to occur. • Earth had to be more than 6000 years old. • He also found marine fossils in the Andes mountains. • He experienced an earthquake that showed him first hand how land underwater was forced above sea level. • What could account for fossils of marine organisms being found on top of modern-day mountain ranges? 10.3: Theory of Natural Selection • Objectives: Compare artificial selection to natural selection. • Examine the factors Darwin considered in forming his theory of natural selection. • Summarize the four principles of natural selection. • Warm Up: Why would Darwin turn to animal and plant breeders as a source of information in studying variation? • Words to Know: Artificial Selection, Heritability, Natural Selection, List 4 Main Principles to the Theory of Natural Selection, Fitness Artificial Selection • • • • • • • • Artificial selection is the process by which humans change a species by breeding it for certain traits. Humans then determine which traits are favorable and then breed individuals that show those traits. Heritability is the ability of a trait to be passed down from one generation to the next. Darwin compared what he learned about breeding to his ideas on adaptation. He concluded that those traits that were not beneficial could be selected out. Darwin applied his views to the “Theory of Natural Selection”. Natural Selection is a mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals. In nature, the environment is the selecting agent. Struggle for Survival • • • • • • Thomas Malthus proposed that resources such as food, water, and shelter were natural limits to population growth. That is, human populations would grow geometrically if resources were unlimited. Instead disease and a limited food supply kept the population smaller. Darwin reasoned a similar situation took place in nature. Darwin proposed that these adaptations arose over many generations and called this process of evolution “descent with modification”. How did Malthus’s economic theory influence Darwin? Natural Selection Explains how Evolution Can Occur • There are 4 main principles to the theory of natural selection: 1. Variation • The heritable differences that exist in every population are the basis for natural selection. • The differences among individuals result from differences in the genetic material of the organisms, whether inherited from a parent or resulting from a genetic mutation. Natural Selection Explains how Evolution Can Occur 2. Over-reproduction • While having many offspring raises the chance that some will survive, it also result in competition between offspring for resources. Natural Selection Explains how Evolution Can Occur 3. Adaptation • • Certain variations allow some individuals to survive better than others. More successful individuals are “naturally selected” to live longer and to produce more offspring that share those adaptations for the environment. Natural Selection Explains how Evolution Can Occur 4. Descent with Modification • • • • • • • • Over time, natural selection will result in species with adaptations that re well suited for survival and reproduction in an environment. More individuals will have the trait in every following generation, as long as the environmental conditions stay the same. Examples: Jaguars 11,000 years ago, many species faced extinction. Jaguars faced a shortage of food due to climate change. Mammals were less available, but reptiles were numerous. Jaguars with larger jaws and teeth were better able to survive and thus pass those traits onto their offspring. In Biology, the term Fitness is a measure of the ability to survive and produce more offspring relative to together member of the population in a given environment. What are the similarities and differences between natural selection and artificial selection? Changing Environments • Ecologists observed an example of natural selection acting on existing traits within a population of medium ground finches on one of the Galapagos Islands. • A drought in 1977 suddenly reduced the amount of small, soft seeds that the finches preferred. • However there were still plenty of large, tough-shelled seeds. • Because the large-beaked finches in the population were able to crack the large, tough seeds, they did not starve. • The next year, they noticed a big increase in they number of largebeak hatchlings and most of the smaller beaked birds died. Adaptations as Compromises • Not all adaptations result in individuals that are perfectly suited to their surroundings. • Ex: Pandas have a structure in their wrist that acts like a thumb. The thumb is actually an enlarged wrist bone that they use to help hold bamboo. It is not considered a true thumb though. • Why is the panda’s “thumb” considered an adaptive compromise? 10.4: Evidence of Evolution • Objectives: Recognize the major sources of evidence for evolution. • Examine the pattern of features that reveal the history of a species. • Warm Up: Why are the larger fossil organisms so different from the animals on Earth today? • Words to Know: List all 9 Evidence of Evolution with definitions. Evidence of Evolution: 1. Fossils • In the late 1700’s geologists wondered why certain types of fossils were found in some layers of rock and not others. • Later studies suggested that the fossil organisms in the bottom, or older, layers were more primitive than those in the upper or newer layers. Evidence of Evolution: 2. Biogeography • Recall that Darwin saw that island plants and animals looked like, but were not identical to, species on the South American continent... • He hypothesized that at some point in the past, some individuals from the South American mainland had migrated to the islands. • Different ecosystems favored different traits and there speciation occurred. • Biogeography is the study of the distribution of organisms around the world. Evidence of Evolution: 3. Comparative Embryology • A study proposing a relationship between crabs, which can walk, and barnacles, which are fixed in one place as adults, fascinated Darwin. • He noticed that immature crabs and barnacles looked similar, but the adults were different. • Comparative embryology now studies those similarities between organisms. • Another example: pharyngeal pouches and “tails” as embryos in a variety of chordates. Evidence of Evolution: 4. Homologous Structures • Homologous structures are features that are similar in structure but appear in different organisms and have different functions. • Ex: forelimbs of tetrapod vertebrates (human hand, bat wing and mole foot). • The limbs look very similar even though they have different functions. Evidence of Evolution: 5. Analogous Structures • Analagous Structures are structures that perform a similar function but are not similar in origin. • Ex: Bat wings and insect wings are both used for flight, but are NOT similar in structure. • Using the terms homologous and analogous, identify which group of structures provides evidence for a common ancestor? Explain. Evidence of Evolution: 6. Vestigial Structures Structural Patterns are Clues to the History of a Species • • • • • Some organisms have structures or organs that seem to lack any useful function, or at least are no longer used for their original purpose. Vestigial Structures are remnants of organs or structures that had a function in an early ancestor. Ex: Snakes share a common ancestor with lizards and dogs. The tiny pelvic bones and hind limbs in many snakes are vestigial structures. Ex: The appendix in humans. It is a remnant of part of the large intestine and was used to help digest cellulose. What are vestigial structures, and how do they demonstrate common ancestry? Evidence of Evolution: 7. Comparative Biochemistry • Comparative Biochemistry: Study of an organism on a biochemical level – for example: the similarities of amino acids in hemoglobin of the blood of various vertebrates. Evidence of Evolution: 8. Genetic Evidence and 9. Direct Observations • Genetic Evidence: for example: DNA similarities between people in certain parts of the world compared to people in other parts of the world. • Direct Observations: observations of evolutionary changes that occur rapidly – for example: penicillinresistant bacteria 10.5: Evolutionary Biology Today • Objectives: Summarize different types of evidence that support evolution. • Recognize the importance of evolution I unifying all branches of biological study. • Warm Up: What was Darwin’s mechanism for explaining the diversity of life? Mendel’s mechanism? • Words to Know: Paleontology Fossils Provide a Record of Evolution • Paleontology is the study of fossils or extinct organisms. • The fossil record is not complete because most living things do not become fossils after they die. • NO fossil evidence has ever contradicted evolution. • Many transitional fossils have been discovered since Darwin’s work to help support his theories. • Why are fossils such as Basilosaurus isis considered transitional fossils? Transitional Fossil Evidence http://www.nature.com/nature/vide oarchive/ancientwhale/ Transitional Fossil Evidence • What has the head of a crocodile and the gills of a fish? • Tiktaalik of course, this 375 million year old fossil splashed across headlines as soon as its discovery was announced in April of 2006. • It is technically a fish, complete with scales and gills — but it has the flattened head of a crocodile and unusual fins. • It has a combination of features that show the evolutionary transition between swimming fish and their descendents, the four-legged vertebrates — a clade which includes amphibians, dinosaurs, birds, mammals, and of course, humans. Molecular and Genetic Evidence • Because all living things have DNA, they share the same genetic code and make most of the same proteins from the same 20 amino acids. • DNA or protein sequence comparisons can be used to show probable evolutionary relationships between species. DNA Sequence Analysis • The sequences of nucleotides in a gene change over time due to mutations. • DNA sequence analysis depends on the fact that the more related two organisms are, the more similar their DNA will be. • Pseudogenes • Sequences of DNA nucleotides known as pseudogenes also provide evidence of evolution. • Pseudogenes are like vestigial structures. • They no longer function but still are carried with functional DNA. Homeobox Genes • Homeobox genes control the development of specific structures. • These sequences are found in everything from fruit flies to humans. • Protein Comparisons • Similarities among cell types across organisms can be revealed by comparing their proteins, a technique called molecular fingerprinting. • Cells from different species that have the same proteins most likely come from a common ancestor. • Ex: light-sensitive cells from an ancient marine worm were found to closely resemble those of cells in the vertebrate eye. • How have protein comparisons helped determine ancestral relationships between organisms? Evolution Unites ALL Fields of Biology • Scientists are still actively studying evolution. • The theory of evolution combined with genetics is sometimes called the Modern Synthesis of Evolutionary Theory. • The field of evolutionary biology is growing fast. • The basic principles of evolution are used in fields such as medicine, geology, geography, chemistry, and ecology. • How can the idea of a common ancestor help us understand new diseases?