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Source: donsmaps.com Chapter 17 and 18: Darwin’s Theory of Evolution Source: http://anthro.palomar.edu/evolve/evolve_2.htm Theory of Evolution Evolution: A gradual process (over millions of years!) by which modern organisms have descended from ancient ancestors Evolution is based on scientific facts, observations and hypotheses Proposed by Charles Darwin… let’s examine his voyage and data. Charles Darwin English naturalist Set sail on a 5 year cruise on the HMS Beagle in 1831 Source: http://anthro.palomar.edu/evolve/evolve_2.htm The Voyage At each stop, Darwin: Made biological and geological observations Collect plant and animal specimens Collected Fossils Darwin Observed Biodiversity – diversity of life Vast number of species Each well adapt to its environment An intriguing geographic distribution of species Estimates calculate there are 10 million species today. This number only represents 1% of all species that ever lived on Earth! The Galapagos Islands: An Important Influence on Darwin Small group of Islands located 1000km west of South America The Islands had very different climates Darwin noticed that plants and animals varied noticeably from island to island. Land Tortoises Source: www.thebestofecuador.com Darwin found the shell shape corresponds to the habitat Lonesome George Figure 15-3 Variations in Shell Shape (p. 371) Darwin’s Thoughts Where did all the animals come from? Where did humans come from? What about fossils? Has everything always been here? How old is the earth? Do plants ever change? What happened to all the dinosaurs? Lab Requirements: typed, stapled 1. 2. 3. 4. Hypothesis (if/then) Procedures (#’d, clear, step by step) Data (clean table – ok if by hand) Analysis (calculations? summary sentences? graph w/labels + title – also ok by hand) 5. Conclusion (follow requirements in ppt) Altogether about 35 points Use weebly documents to guide you! Darwin’s Proof Evidence of Evolution The Fossil Record Geographical Distribution Similarities • Embryology • Chemical Compounds • Body Structures Evidence in support of evolution: Fossil record Geologic time scale Geographic distribution of species Embryology Anatomy (“body structure comparisons”) Chemical comparisons (DNA/RNA, Protein) The Fossil Record By comparing older fossils with younger fossils, evidence of change is clear. Geologic Time Scale The age of Earth provides evidence that time was available for evolution of species Precambrian 4.6 bya-544 mya Paleozoic 543-245 mya (cambrian explosion) Mesozoic 245-67 mya Cenozoic 66 mya to present Radiometric vs. Relative Dating ½ Life of Elements Decay Depths of Strata Geographic Distribution of Living Species Darwin discovered the existence of similar but unrelated species in different locations Darwin later realized the similar animals were products of different lines of evolutionary descent. Similarities in Early Development Early1900’s: embryos thought to look the same Current knowledge: • Common genes play a role in early development • Later stages show differences in embryos • Differences are from genes that have changed due to evolution Similarities in Early Development Similarities in Body Structure Evolutionary change alters structure and appearance based on their FUNCTION Why? Structures that allow organisms to survive in their environment increases fitness Homologous Structures: • Limbs or body parts that resemble one another in structure -However, these may offer different functions -They suggest common ancestry of organisms That experienced divergent evolution Analagous Structures Similar function, but highly unique structure Vestigial Organs Organs that have no or little purpose. Evolution has lead to adaptations that suit particular organisms Similarities in Chemical Compounds All organisms use DNA and/or RNA Many organisms have similar proteins The more closely related two species are, the more their chemical properties resemble each other. Evidence for Evolution Ticket Out 1. Name at least four forms of evidence in support of the theory of evolution. Challenge: name ALL 6 discussed! 2. Why are structures like our tailbone, wisdom teeth and the appendix evidence that evolution has occurred? Darwin Presents His Case Darwin reflected on his findings for many years after returning home. He wrote about his theories in, On the Origin of Species. Published in 1859 23 years after the voyage of the Beagle http://www.pbs.org/wgbh/evolution/educators/teachstud s/svideos.html Inherited Variation vs. Artificial Selection Variations: Different forms or ‘alleles’ for a trait Inherited Variations Traits passed on from parent to offspring Artificial Selection (ex. dog breeding) Humans select useful variations from naturally occurring traits Selective breeding practices Evolution by Natural Selection The Struggle for Existence Darwin thought nature used an “artificial selection process” Members of each species compete for resources Natural Selection (hummingbird video?) Processes in nature that over time results in only the survival of the fittest species Results in changes of inheritable characteristics of a population. Changes increase a species’ fitness in its environment Survival of the Fittest Fitness Ability of an individual to survive and reproduce. Fitness is a result of adaptations Adaptation Physical and behavioral traits that allow an organism to survive in its environment Darwin Concluded: Over long periods of time, natural selection produces organisms that have different Structures Niches Habitats Species descended with modifications from a common ancestor. Implies all living things are related to one another This principle is known as common descent Darwin’s Finches Similarities can be explained with Darwin’s theory: Living organisms evolved with gradual modification of earlier forms of an ancestor with common descent. Let’s Look at an Example… In pre-industrial England, there was a species of moth called the Peppered Moth (Biston betularia) Almost all peppered moths were gray with dark flecks Rarely were they black The Peppered Moth The peppered moth tend to rest on tree trunks during the day The gray moth were well camouflaged on the gray tree trunks Black moths stand out and are easy targets for birds. The Peppered Moth Now, turn to England during Industrial Times… Pollution from the factories turned tree trunks black with soot. Now, the black moths were camouflaged on the trees. The Peppered Moth The black moths had a better chance of survival They had a higher fitness After many moth generations, almost all the months in industrial areas were black The Peppered Moth Black coloration is an adaptation to an environment with black tree trunks In an industrial environment, black moths survive to reproduce better than gray moths. Therefore, their genes are passed on to future generations Tix out? Why did the peppered moth change color over many generations in England? 2-3 sentences, use the word adaptation AND fitness Mechanisms of Evolution 1. Population Genetics and Evolution 2. The Evolution of Species 3. Patterns of Evolution 1. Population Genetics and Evolution Populations evolve, individuals don’t Natural processes can lead to changes in a population’s gene pool. Gene pools • (genotypes vs. phenotypes) Allele frequency Genetic equilibrium 1. Population Genetics and Evolution Changes in Genetic equilibrium lead to evolution Genetic drift (changes to allele freq. by random chance) Mutations Migration Natural disasters 1. Population Genetics and Evolution Natural selection acts upon variation in populations A. Stabilizing Selection: • favors average individuals B. Directional Selection: • favors the one extreme form C. Disruptive Selection: • favors both extremes 2. The Evolution of Species Speciation: The development of a new species which can no longer interbreed or produce fertile offspring with it's original ancestor. In other words: the evolution of a new species 2. The Evolution of Species Physical barriers can prevent interbreeding Geographic isolation • Prevents gene flow between populations 2. The Evolution of Species Geographic isolation can lead to reproductive isolation • Inability to breed, or mating behaviors change • Behavioral isolation Chromosome alternations cause speciation Errors in chromosomes result in ‘polyploid’ organisms 2. The Evolution of Species Speciation can occur rapidly or slowly Gradualism vs. punctuated equilibrium 3. Patterns of Evolution Species diversify when introduced to new environments Adaptive radiation Divergent evolution homologous structures are evidence of this Patterns of Evolution Distantly related species can evolve similar features Convergent evolution Analogous structures are evidence of this