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Unit 5- Evolution Write your definition of Evolution. Scientist’s Comments What is Evolution? • Common descent • Organisms are descended from a common ancestor. • All organisms are related to a common ancestor. • Common descent of living forms • With common descent things change common ancestor and that more complex forms of life descended from less complex forms. 4. Jean-Baptiste Lamarck – Proposed that changes in the environment caused an organism’s behavior to change and that these changes would pass on to their offspring. He called this the inheritance of acquired characteristics. Early views of earth • Before Darwin, it was believed that the earth and its environment was the same now as in the beginning. • Change over time • Evolution is the change in various characteristics of organisms • Read pages 298 – 301 in your Biology Textbook • What beliefs influenced men’s opinions of the origin of life on earth before Darwin came up with his Theory of Evolution? • What 4 scientists made contributions to our knowledge of evolution before Darwin? • What theory of geologic change set the stage for Darwin’s theory? Early Ideas Before The Theory of Evolution: Early Views • Man’s early views were influenced by teachings from the Bible. • The Age of the Earth was a key issue in early debates concerning evolution. • The age of the earth was believed to be 6,000 years. Darwin was not the first person to come up with ideas about evolution. Four scientists in particular were important: 1. Carolus Linnaeus – Proposed that plants changed through hybridization. 2. Georges Leclerc – Proposed that species shared ancestors. Also rejected the idea that the earth was only 6000 years old. 3. Erasmus Darwin – Darwin’s grandfather Proposed that all living things descended from a • Man’s views of early earth was based upon 3 concepts: 1. Theory of Catastrophism –Natural catastrophic events such as volcanoes, floods and earthquakes were responsible for mass extinctions. 2. Gradualism – –Changes on earth occurred by small steps over a long period of time. 3. Uniformitarianism – Rock strata ( layers ) demonstrate that geologic processes add up over long periods of time to cause great changes in the earth’s crust. Pre-learning questions…. What does evolution mean? A) When a monkey changes into a human B) Caterpillar changes to a butterfly C) Change in a species over time D) When bacteria turn into viruses Video Questions Origins of Earth • Answer these questions after reading the textbook pages 368-371 1. Describe the scientific explanation for the origin of earth. •2. Describe the conditions present during the time earth was forming. Evolution Evolution -A change in species over time Father of Evolution -Charles Darwin -traveled to Galapagos Islands in 1800s to study plants & animals -He observed unique species and interesting changes in their structure STOP THINK AND REVIEW… Name one organism that Darwin saw in the Galapagos that had never been seen before Examine the pictures in the slide presentation 1) What do you see? 2) What is this an example of? 3) How might the appearance of this insect help it to survive? How did Darwin justify his Theory of Evolution? • Darwin began his voyage thinking that species could not change. • He knew that man had “forced” change through artificial selection or what we call selective breeding. b) Sea iguanas Darwin said nature “selected” those organisms who would survive to reproduce and make offspring better suited to survive their environments. This was how Darwin proposed that organisms evolve. c) Turtles Natural Selection a) Peacocks d) Duck billed platypus Darwin’s Book -Data gathered from journey led him to write a book in 1859 -“Origin of Species By Means of Natural Selection”-most famous science book ever written -it was extremely controversial because it was proposing the idea that species evolve, which contradicted the Bible Scopes Trial • In 1925, a school teacher – John Scopes was prosecuted for teaching Darwin’s theory of evolution to his students • Nick named “The Monkey Trial” • William Jennings Bryan vs Clarence Darrow • Scopes lost and was found guilty. Ordered to pay $100 fine. • Organisms well suited to their environment survive longer and reproduce in greater numbers than those less suited. In other words… • Individuals that have inherited beneficial adaptations produce more offspring on average that other individuals. Which of the following would be an example of an organism being well suited to its environment? a) Bird with wings that can’t fly b) Lizard blending in with the leaves c) Brightly colored moth on a tree d) Animals with extra fur in the summer • 5 Factors that make Natural Selection Work STOP THINK AND REVIEW… 1. Variation- all species have genetic differences What made Darwin’s book so controversial? 2. Struggle for Existence -All species compete for survival a) It proposed that organisms change over time b) It went against the common belief in God and creationism c) It contradicted the Bible d) All of these 3. Only some survive -some survive life’s challenges better than others 4. Genetic change -offspring are the result of successful parents. 5. Adaptation- some organisms can make changes to be bette suited to their environment. Ex: camouflage, thicker fur, burrowing in the desert Evidences of Evolution • Fossil Records - Preserved or mineralized remains or imprint of an organism that lived long ago. (formed by time, heat, pressure) • Fossils show change in body structure over time. Vestigial Structures -Organs that no longer serve a useful purpose or function. -EX: Wisdom Teeth, Tail bone Pelvic bone in Whale Homologous Structures The more similar an organisms _____, the more closely they are related. a) DNA b) Limbs c) Bones d) Head structure A structure that no longer serves a useful purpose or function is called: a) Homologous b) Fossil c) Vestigial d) Embryonic An example of a structure that no longer serves a purpose would be: • Parts that are similar in structure – show possible common ancestry a) Tailbone • EX: arm of human, wing of a bird, fin of a dolphin c) Pelvic bone on a whale b) Wisdom teeth d) All of these DNA Similarity • Scientists look at DNA to see evolutionary relationships (similarities) Homologous structures (parts that are similar in structure but different in function) may show… a) Incorrect fossil records • More similar the DNA, the more closely they are related Embryo Studies -embryos with similarities show possible common ancestry -EX: humans, chickens, fish all have gill slits & tails b) 2 organisms may have come from a common ancestor c) Similar function in organisms d) That organisms are unrelated Left Side Output Create a “Tree Map” Evidence for Evolution STOP THINK AND REVIEW Draw a picture to represent each one Scientist can analyze these to see how body structures have changed over time: Other Mechanisms of Evolution Translation: What are some other causes of Evolution? A) Vestigial structures B) Homologous structures C) Fossils D) Limb structure 1. Gene Flow • the movement of alleles between populations. • occurs when individuals join new populations and reproduce. • keeps neighboring populations similar. • Low gene flow increases the chance that two populations will evolve into different species. 2. Gene Drift • a change in allele frequencies due to chance. • causes a loss of genetic diversity. • most common in small populations. • Causes of Genetic Drift • A population bottleneck event. – occurs when an event drastically reduces population size. • The founding of a small population – occurs when a few individuals start a new population – Genetic drift has negative effects on a population • • less likely to have some individuals that can adapt harmful alleles can become more common due to chance 3. Sexual Selection • What would you use to measure the changes if they were taking place? The Hardy-Weinberg Model • 2 scientists ( Hardy & Weinberg ) developed an ideal model to use to compare with any population. • Their model showed that: 1. genotype frequencies ( how often a trait occurs ) in a population stay the same over time as long as certain conditions are met. 2. Future genotypic frequencies could be predicted. • The model identified the 5 conditions needed for a population to remain at equilibrium.( to stay the same ) • HWB Criteria • It must be a large population • It must be a large population • No immigration or emigration • No mutations • Must have Random Mating –( no sexual selection ) • No Natural Selection occurring Summation of Evolution Summation of Evolution • occurs when certain traits increase mating success. • There are 5 factors that lead to evolution… • occurs due to higher cost of reproduction for females. 1. Genetic Drift Changing gene frequencies due to chance. 2. Gene Flow Two types of sexual selection. –intrasexual selection: competition among males –intersexual selection: males display certain traits to females Hardy-Weinberg Equilibrium Think about it… • If you were studying a population of animals to see if they were evolving… • How would you know how they were changing? Movement of alleles from one population to another. 3. Mutation New alleles form due to mutations in the DNA. 4. Sexual Selection Certain traits may improve mating success. 5. Natural Selection Certain traits may be an advantage for survival.