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Theory of Evolution In your own words, describe what YOU think the theory of evolution means… Charles Darwin Darwin’s Theory of Evolution Evolution, or change over time, is the process by which modern organisms have descended from ancient organisms. A scientific theory is a well-supported testable explanation of phenomena that have occurred in the natural world. How do you think Darwin came up with his theory? Voyage of the Beagle Voyage of Beagle Dates: February 12th, 1831 Captain: Charles Darwin Ship: H.M.S. Beagle Destination: Voyage around the world. Findings: evidence to propose a revolutionary hypothesis about how life changes over time Patterns of Diversity Darwin visited Argentina and Australia which had similar grassland ecosystems. those grasslands were inhabited by very different animals. neither Argentina nor Australia was home to the sorts of animals that lived in European grasslands. Patterns of Diversity Darwin posed challenging questions. Why were there no rabbits in Australia, despite the presence of habitats that seemed perfect for them? Why were there no kangaroos in England? Living Organisms and Fossils Darwin collected the preserved remains of ancient organisms, called fossils. Some of those fossils resembled organisms that were still alive today. Living Organisms and Fossils Others looked completely unlike any creature he had ever seen. As Darwin studied fossils, new questions arose. Why had so many of these species disappeared? How were they related to living species? Fossils The Galapagos Island The smallest, lowest islands were hot, dry, and nearly barren-Hood Island-sparse vegetation The higher islands had greater rainfall and a different assortment of plants and animals-Isabela- Island had rich vegetation. The Galapagos Island Darwin was fascinated in particular by the land tortoises and marine iguanas in the Galápagos. Giant tortoises varied in predictable ways from one island to another. The shape of a tortoise's shell could be used to identify which island a particular tortoise inhabited. There are finches on the mainland and on all the islands The finches are very similar except for their beaks The beaks differ from island to island The beaks are always a match to the food source. Darwin reasoned the finches began as a single species in Equator As competition for space & food increases, some finches fly to one of the islands. The food source on that island is slightly different, finches lucky enough to have the ‘right’ beak for the new food – eat, grow, develop, reproduce & pass on that “beak” trait. Over time, more & more of the finches have the ‘new’ beak A new species of finch begins. Repeat to other islands What did Darwin find out? How did Darwin interpret his observations? Observation Inference Very similar birds All finches Lots of variation Lots of competition Environment can only support a limited number of birds By chance, some birds inherit beaks that enable them to eat different foods Eat – survive -- reproduce – Pass on “good” trait Group 1 Group 2 Original beak New beak The birds share common ancestry Similar birds Different beaks Different food sources More birds can share same environment because they are not eating the same food Natural Selection - Species change, morph toward better balance with environment - One species splits into 2 species Animals found in the Galapagos Land Tortoises Darwin Finches Blue-Footed Booby Marine Iguanas Animals The Journey Home Darwin Observed that characteristics of many plants and animals vary greatly among the islands Hypothesis: Separate species may have arose from an original ancestor To understand how radical Darwin’s thoughts appeared, you must understand a few things about the world in which he lived Most Europeans belived the world was only a few thousand years old Nothing had changed since creation Rocks and major geological features were thought to have been produced suddenly by catastrophic events that humans rarely ever witnessed Slowly after studying many scientific theories of his time, Darwin began to change his thinking dramatically Hutton and Lyell Geological forces that have shaped Earth form very slowly, often over millions of years Hutton and Geological Change Geological forces that have shaped Earth form very slowly, often over millions of years Therefore Earth had to be much more than a few thousand years old Lyell’s Principles of Geology Lyell – author “Principles of Geology” Process that shaped the Earth millions of years earlier continue in the present Darwin Thought: If the earth could change over time, could life be changing as well? Charles Lamarck Lamarck’s Theory of Evolution Tendency toward Perfection(Giraffe necks) Use and Disuse (bird’s using forearms) Inheritance of Acquired Traits Lamarck’s Evolution Hypothesis Jean – Baptiste Lamarck French naturalist One of the first scientists to recognize that living things have changed over time, and that all species were descended from other species Also realized, that organisms were somehow adapted to their environments Lamarks theory had 3 aspects to it Tendency toward perfection Organsims continually change and acquire features that help them live more successfully Ex.) Birds wanted to fly, so their wings grew and became suited to flying 1. 2. Use and Disuse Body parts that were used developed, and those that were not went away Ex.) Reptiles stopped using their legs and evolved into snakes 3. Evolution of Acquired Traits Organsims that changed a characteristic in their lifetime, would pass that change on to its offspring This theory is WRONG! The Science Theory of Evolution • Species* change over time and space – staying a good match to their environment • All organisms share common ancestors with other organisms. explains the similarities of organisms & the inheritance of traits The primary mechanism of change over time is natural selection. species - populations of interbreeding organisms Natural Selection Natural Selection & Artificial Selection Natural variation--differences among individuals of a species Artificial selection- nature provides the variation among different organisms, and humans select those variations they find useful. Adaptation when an organism becomes better fitted to survive and multiply in its environment. Evolution by Natural Selection The Struggle for Existence-members of each species have to compete for food, shelter, other life necessities Survival of the Fittest-Some individuals better suited for the environment Struggle For Existence & Survival of The Fittest Natural Selection Over time, natural selection results in changes in inherited characteristics of a population. These changes increase a species fitness in its environment Extinct Species a species that no longer exists anywhere on earth Classification/Taxonomy biological classification is a system which is used to organize and codify all life on Earth. 2 ways the present day chicken is better adapted to today’s environment than its ancestor would have been 1. smaller size – needs less food for survival, 2. has feathers rather than fur – lighter and water resistant – can fly? Descent Descent with Modification-Each living organism has descended, with changes from other species over time Common Descent- were derived from common ancestors Evidence of Evolution The Fossil Record Geographic Distribution of Living Things Homologous Body Structures Similarities in Early Development Evidence for Evolution The Fossil RecordLayer show change Geographic Distribution of Living Things Homologous Body Structures Similarities in Early Development Evidence of Evolution The Fossil Record Geographic Distribution of Living Things-similar environments have similar types of organisms Homologous Body Structures Similarities in Early Development Homologous Structures Homologous Structures-structures that have different mature forms in different organisms, but develop from the same embryonic tissue Evidence for Evolution Vestigial organs-organs that serve no useful function in an organism i.e.) appendix, miniature legs, arms Similarities in Early Development DNA deoxyribonucleic acid: an extremely long macromolecule that is the main component of chromosomes and is the material that transfers genetic characteristics in all life forms Genetic Diversity - the level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species. Phenotype is an organisms observable characteristics which are influenced both by its genotype and by the environment. Genotype is the set of genes that an organism carries. Similarities in Embryology Many embryos look especially similar during early stages of development All vertebrates go through a stage in which they have gill pouches Similarities suggest an evolutionary relationship among all vertebrate species Nature at Work Intro Mendel’s Work Gene A segment of DNA that codes for a particular protein. Gene Pool All the genes of all the members in a population. Nature at Work Intro Mendel’s Work Vocab: Allele Dominant Recessive Pure bred Hybrid Genotype phenotype Mutation - A mutation occurs when a DNA gene is damaged or changed in such a way as to alter the genetic message carried by that gene. Selective Pressure Any environmental factor that favors one trait over another. Genetics – working (non-technical) definitions Allele The variations a trait comes in Tall, short (inherit 1 allele from each parent) Dominant The allele that will show if it is present T Recessive Only shows when both alleles are recessive tt Present but not showing when dominant is present Tt Pure bred Both inherited alleles are the same TT or tt Hybrid Inherits 1 dominant & 1 recessive allele from parents Tt Genotype The gene type TT, Tt, tt Phenotype The visible trait Evidence of Evolution DNA How does DNA support the Theory of Evolution? DNA has double helix structure All animal DNA very similar (except human) Plant DNA similar but with less chromosome pairs All DNA has similar nucleic acids Summary of Darwin’s Theory 1. 2. 3. 4. Individual organisms in nature differ from one another. Some of this variation is inherited Organisms in nature produce more offspring than can survive, and many of those that survive do not reproduce. Because more organisms are produced than can survive, members of each species must compete for resources. Because each organism is unique, each has different advantages and disadvantages in the struggle for existence.