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Evolution Unit Chapters 10 and 11 1 History of Evolutionary Thought copyright cmassengale 2 Evolutionary Timeline copyright cmassengale 3 Early Ideas On Earth’s Organisms Linnaeus – 1st to group similar organisms and assign them Latin names Two word name (Genus species) Known as Binomial nomenclature copyright cmassengale 4 : Contributor’s to Darwin’s thinking included: Leclerc de Buffon – proposed that species shared ancestors instead of arising separately Erasmus Darwin – organisms could evolve from a common ancestor copyright cmassengale 5 : Contributor’s to Darwin’s thinking included: Cuvier – Catastrophism – Stated that species disappear due to a catastrophic event of the earth’s crust (volcano, earthquake…) Hutton – Gradualism – Changes on Earth formed as product of slow but continuous and cumulative processes copyright cmassengale 6 Contributor’s to Darwin’s thinking included: Charles Lyell –Uniformitarianism – Geologic processes that shape the Earth are uniform through time Alfred Wallace – organisms evolved from common ancestors copyright cmassengale 7 Lamarck’s Theory of Evolution Was first scientist to recognize that organisms have changed over time Stated that changes are adaptations to environment acquired in an organism’s lifetime Said acquired changes were passed to offspring copyright cmassengale 8 Lamarck’s Theory of Evolution Law of Use and Disuse – Organisms Could Change The Size Or Shape Of Organs By Using Them Or Not Using Them – If a body part were used, it got stronger – If body part NOT used, it deteriorated copyright cmassengale 9 Lamarck’s Theory of Evolution Inheritance of Acquired Characteristics – idea that an organism can pass on characteristics that it acquired during its lifetime to its offspring – Over Time This Led To New Species copyright cmassengale 10 copyright cmassengale 11 Lamarck’s Mistakes Lamarck’s theories were INCORRECT! Lamarck Did NOT Know how traits were inherited (Traits are passed through genes) – Genes Are NOT Changed By Activities In Life – Change Occurs Through Mutations Before An Organism Is Born copyright cmassengale 12 Charles Darwin the Naturalist copyright cmassengale 13 Voyage of the Beagle Charles Darwin Joined Crew of HMS Beagle, 1831 Naturalist 5 Year Voyage around world Become known as the “Father of Evolution” Astounded By Variety of Life Wrote “The Origin of Species” copyright cmassengale 14 Darwin’s Voyage of Discovery A reconstruction of the HMS Beagle sailing off Patagonia. copyright cmassengale 15 Darwin Left England in 1831 copyright cmassengale Darwin returned 5 years later in 1836 16 HMS Beagle’s Voyage copyright cmassengale 17 The Galapagos Islands Small Group of Islands West of South America Very Different Climates Animals On Islands Unique »Tortoises »Iguanas »Finches copyright cmassengale 18 The Galapagos Islands Volcanic islands off the coast of South America Island species varied from mainland species & from island-toisland species Each island had long or short neck tortoises copyright cmassengale 19 copyright cmassengale 20 The Galapagos Islands Finches on the islands resembled a mainland finch More types of finches appeared on the islands where the available food was different (seeds, nuts, berries, insects…) Finches had different types of beaks adapted to their type of food gathering copyright cmassengale 21 copyright cmassengale 22 Darwin’s Observations & Conclusions copyright cmassengale 23 Voyage of the Beagle – During His Travels, Darwin Made Numerous Observations And Collected Evidence That Led Him To Propose A Revolutionary Hypothesis About The Way Life Changes Over Time copyright cmassengale 24 Darwin’s Observations Patterns of Diversity were shown Unique Adaptations in organisms Species Not Evenly Distributed » Australia, Kangaroos, but No Rabbits » S. America, copyright cmassengale Llamas 25 Definition • Evolution is the gradual change in a population of organisms over time copyright cmassengale 26 Darwin’s Observations Left unchecked, the number of organisms of each species will increase exponentially, generation to generation In nature, populations tend to remain stable in size Environmental resources are limited. copyright cmassengale 27 Darwin’s Conclusion • Production of more individuals than can be supported by the environment leads to a struggle for existence among individuals • Only a fraction of offspring survive each generation • Survival of the Fittest copyright cmassengale 28 Darwin’s Observations • Individuals of a population vary extensively in their characteristics with no two individuals being exactly alike. • Much of this variation between individuals is inheritable. copyright cmassengale 29 Darwin’s Conclusion Individuals who inherit characteristics most fit for their environment are likely to reproduce more offspring than less fit individuals. The unequal ability of individuals to survive and reproduce leads to a gradual change in a population, with favorable characteristics accumulating over generations. This is called Natural Selection copyright cmassengale 30 Darwin’s Theory of Evolution Organisms Change Over Time copyright cmassengale 31 Natural Selection Driving force for evolution During the struggle for resources, the strongest survive & reproduce Idea that at least some of the differences between individuals, which impact their survival and fertility, are inheritable Therefore, natural selection acts upon mutations. . 32 copyright cmassengale Origin of Species Darwin Presents His Case copyright cmassengale 33 Publication of “On The Origin of Species” Upon His Return To England, Darwin Developed His Observations Into The Theory of Evolution But He Did Not Publish For 25 Years – Why? copyright cmassengale 34 Publication of “The Origin of Species” Darwin Knew That His Theory Would Be Extremely Controversial And Would Be Attacked His Theory Challenged Established Religious & Scientific Beliefs copyright cmassengale 35 Publication of “On The Origin of Species” He Refused To Publish Until He Received An Essay From Alfred Wallace – Fellow Naturalist – Independently Developed The Same Theory – After 25 Years, Someone Else Had Come To The Same Conclusions From Their Observations Of Nature copyright cmassengale 36 Wallace’s Contribution • Alfred Wallace: • Independently came to same Conclusion as Darwin that species changed over time because of their struggle for existence • When Darwin read Wallace’s essay, he knew he had to publish his findings copyright cmassengale 37 Natural Variation and Artificial Selection Abandoned The Idea That Species Were Perfect & Unchanging Observed Significant Variation in All Species Observed Observed Farmers Use Variation To Improve Crops & Livestock – Called Selective Breeding copyright cmassengale 38 Natural Variation and Artificial Selection Natural Variation – Differences Among Individuals Of A Species Artificial Selection – Selective Breeding To Enhance Desired Traits Among Stock or Crops copyright cmassengale 39 Natural Variation and Artificial Selection Key Concept: In Artificial Selection, Nature Provided The Variation Among Different Organisms, And Humans Selected Those Variations That They Found Useful copyright cmassengale 40 Evolution by Natural Selection Concepts copyright cmassengale 41 Four Main Principles of Natural Selection Genetic Variation Overpopulation Adaptation Descent with Modification 42 Genetic Variation Genetic Variation – Variations come from mutations and gene shuffling that result from sexual reproduction. – In genetics terms, evolution is any change in allele frequency in a population. 43 Overpopulation Overproduction: Organisms reproduce more than its environment can handle. – Overproduction leads to competition – Competition: the struggle for existence » Organisms compete for food, living space, and reproduction. 44 Adaptation Adaptation – Inherited Characteristic That Increases an Organisms Chance for Survival Examples of Adaptations – Mimicry: one species mimics (imitates) the color, pattern, or behavior of another in order to gain protection – Camouflage: a species’ ability to conceal itself from its predators by blending into45its environment. Mimicry Which is the poisonous snake?? • Another example of mimicry involves the monarch butterfly, which is toxic and very nasty when eaten. Its bright orange coloration is a warning to birds to leave it alone. The non-toxic viceroy butterfly has developed colors and wing patterns that are very similar to those of the monarch and so most birds won’t take a chance by taste-testing it! 46 Camouflage 47 Descent with Modification Darwin proposed that organisms descended from common ancestors Idea that organisms change with time, diverging from a common form Caused evolution of new species with better adaptations 48 Survival of the Fittest Fitness – Ability of an Individual To Survive & Reproduce – Fitness is central to the process of evolution Individuals With Low Fitness – Either Die or Produce Few Offspring Survival of the Fittest AKA Natural Selection 49 Survival of the Fittest Key Concept Over Time, Natural Selection Results In Changes In The Inherited Characteristics Of A Population. These Changes Increase A Species Fitness In Its Environment 50 Theory of Evolution Today Supporting Evidence copyright cmassengale 51 Evidence of Evolution Darwin Argued That Living Things Have Been Evolving On Earth For Millions of Years. Evidence For This Process Could Be Found In: – The Fossil Record – The Geographical Distribution of Living Species – Anatomical Structures of Living Organisms – Similarities In Early Development copyright cmassengale 52 Fossil Record Fossils In Different Layers of Sedimentary Rock showed evidence of gradual change over time Fossil: preserved remains of ancient organisms Fossil Record: provides evidence about the history of life on Earth – Most fossils form in sedimentary rock ______________________ Fossils that are found in a lower layer are older than fossils that are found in a higher strata Fossils Radioactive (Radiometric) dating – Technique used to calculate age of fossils based on the amount of remaining radioactive isotopes it contains » Age of fossil is based on half-lives Half life: length of time required for half of the radioactive atoms in a sample to decay Half-life Practice Problems What percentage of a radioactive element will be left after: – a. 1 half-life b. 2 half-lives c. 3 half-lives If a rock sample originally contained 12 g of Uranium-235, how much will be left after: – a. 1 half-life b. 2 half-lives c. 3 half-lives Gold-198 has a half-life of 2.7 days. How much of a 96 g sample of gold-198 will be left after 8.1 days? 56 Comparative Anatomy Homologous Structures: Same structure with a different function copyright cmassengale 57 Comparative Anatomy Analogous Structures: Different structures that have the same function copyright cmassengale 58 Comparative Anatomy Vestigial Organs: Remnants of structures that were functional in ancestral species – Organs or structures that have lost their function in the organism and have become reduced in size – Modern animals may have structures that serve little or no function » Example: Appendix In Man Eyes on a cave fish (blind) 59 Comparative Embryology Comparative embryology: comparing the formation and development of embryos – Embryo – early stages of vertebrate development Early stages of development in many vertebrates are very similar – Same development order – Similar tissues and organ structure such as gills and a tail – Similar features in young embryos suggest evolution from a distant common ancestor 60 A B C D E F G H 61 Biochemistry All living things are biochemically similar. Similarities in amino acid sequences can determine relatedness. 62 Geographic Distribution of Living Species Biogeography: – Different Animals On Different Continents But Similar Adaptations To Shared Environments copyright cmassengale 63 3 Ways Natural Selection Affects Phenotype Distribution 1. Directional Selection 2. Stabilizing Selection 3. Disruptive Selection Directional Selection Individuals at one end of a distribution curve have a higher fitness than individuals in the middle or at the other end – In diagram, birds w/ big beaks have higher fitness Key Directional Directional Selection Directional Selection Selection Food becomes scarce. Food becomes scarce. Low mortality, Low mortality, high fitness high fitness High mortality, High mortality, low fitness low fitness Stabilizing Selection Individuals near the center of the curve have higher fitness than individuals at either end – In this diagram, birds w/ median birth weight have higher fitness than heavy or light weight birds Stabilizing Selection Stabilizing Selection KeyStabilizing Selection Key Low mortality, Low mortality, high fitness high fitness High mortality, High mortality, low fitness low fitness Birth Weight Birth Weight Selection Selection against both against both extremes keep extremes keep curve narrow curve narrow and in same and in same place. place. Disruptive Selection Individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle – In diagram, birds with small and large beak sizes have higher fitness than birds with a medium beak size Disruptive Selection Disruptive Selection Beak Beak Size Size Population splits Population splits into two subgroups into two subgroups specializing in specializing in different seeds. different seeds. Number of Birds Low mortality, high fitness High mortality, low fitness of Birds Number in Population in Population Key Key Number of Birds Largestand andsmallest smallestseeds seedsbecome becomemore morecommon. common. Largest of Birds Number in Population in Population Beak Beak Size Size Patterns of Evolution Three patterns of evolution: – Convergent Evolution – Divergent Evolution – Coevolution copyright cmassengale 68 Convergent Evolution Convergent Evolution – Evolution toward similar characteristics in unrelated species – Analogous structures are examples of convergent evolution. Divergent Evolution Divergent Evolution – When closely related species evolve in different directions – Also called adaptive radiation 70 Coevolution Sometimes organisms that are closely connected to one another by ecological interactions evolve together. Example: Flowering plants and a specific pollinator Coevolution: Two species evolve in response to changes in each other.