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Transcript
Evolution Early Ideas • SPONTANEOUS GENERATION – Idea that life arose from non-living things – Example: Flies from rotten meat Early Ideas • BIOGENESIS – Life comes from life • Example: Spiders lay eggs Darwin’s Ideas *History of Evolution • The theory of evolution existed before Darwin. – Wallace – Lamarck • It was his Theory of Natural Selection that became widely accepted. *History of Evolution • Before Darwin, it was believed that the Earth and its organisms were young and that they did not change. • In 1831, Darwin began a voyage around the world on a ship, the H.M.S. Beagle. History of Evolution • Galapagos Islands – Volcanic islands off the South American coast • Island species varied from the mainland species, and from island-to-island – Example: Each island had either long or short necked tortoises depending on the island's vegetation History of Evolution • Darwin concluded that adaptation to the environment can cause diversification, including origin of new species. *History of Evolution • In 1859, Darwin published his ideas in a book called The Origin of Species • Made the argument that organisms change over time to better suit their environment Natural Selection • NATURAL SELECTION – Organisms that are most fit for the environment will survive & reproduce • Their traits will be passed on to the next generation • Over time, population will evolve to have the trait Natural Selection • 4 criteria for natural selection to occur 1. Variation between organisms 2. Over-production causes competition 3. Traits are passed on (heredity) 4. Some organisms survive/reproduce more than others Why must we meet these conditions? Imagine this scenario: All females genetically identical All males genetically identical No one female or male is “more fit” than the other, therefore no reason to choose one male or female over another All matings result in the same offspring Or this scenario… Important Evolution Facts • Natural selection acts on individuals – Individual organisms are selected for or against • Populations evolve – Not individuals! Natural Selection • Over time, organisms will develop ADAPTATIONS to their environment – Increase an organism’s FITNESS • FITNESS – ability of an organism to survive and reproduce Types of Adaptation • 3 main types of adaptations: 1. STRUCTURAL • Unique body structures • thorns on roses, webbed feet 2. PHYSIOLOGICAL • Unique chemicals or biochemical abilities • poisons in snakes, antibiotic resistance 3. BEHAVIORAL • Unique behaviors • bird migration, plants growing toward light Grasping - Raptors use their large curved claws to snatch fish from the water. Scratching - Pheasants scratch the soil for food & have nail-like toes. Swimming - Ducks use their feet like paddles. Perching - Robins have a long back toe, which lets them grab a perch tightly. Running - Many fast-running birds have three toes rather than four. Climbing - A woodpecker's hind toes enable it to climb without falling backward. Types of Adaptations • Important structural adaptations – CAMOUFLAGE • Blending in to the environment – MIMICRY • Mimicking a dangerous organism to scare predators CAMOUFLAGE MIMICRY PHYSIOLOGICAL BEHAVIORAL Creation of New Species • SPECIATION – organisms acquire enough unique adaptations to become their own species Creation of New Species • Different types of selection can lead to speciation Types of Selection • STABILIZING – An intermediate phenotype is favored • Acts against individuals who deviate too far from the average Selection for average size spiders Normal variation Example: Human Birth Weight Types of Selection • DIRECTIONAL SELECTION – Favors individuals with extreme values of a trait • causes the population to evolve in a particular direction Normal variation Selection for longer beaks Example: Peppered Moth Types of Selection • DISRUPTIVE SELECTION – Favors phenotypes of opposite extremes; disfavors intermediate phenotypes Selection for light limpets Normal variation Selection for dark limpets Which type of selection is it? Early breeders were interested in dogs with the greatest speed. They carefully selected from a group of hounds those who ran the fastest. From their offspring, the greyhound breeders again selected those dogs who ran the fastest. By continuing this selection for those dogs who ran faster than most of the hound dog population, they gradually produced a dog who could run up to 40 mph. Which type of selection is it? Suppose there is a population of rabbits, those with black fur and those with white fur. If this population of rabbits were put into an area that had very dark black rocks as well as very white colored stone, what type of selection would you expect to occur? Which type of selection is it? The Siberian Husky is a medium dog, males weighing 35-60 lbs. The Siberian Husky is well designed for working in the snow. If the Siberian Husky had heavier muscles, it would sink deeper into the snow, so they would move slower or would sink and get stuck in the snow. Yet if the Siberian Husky had lighter muscles, it would not be strong enough to pull sleds and equipment, so the dog would have little value as a working dog. Microevolution • How can you tell if a population is evolving? – Measure the allele frequency from one generation to the next What could be causing the population to change? 50% white : 50% black 100% black 50% BB : 50% bb 100% bb Microevolution • GENE POOL – All the alleles available in a population – Large gene pool = high genetic diversity • Increased fitness levels • More likely to survive environmental changes Microevolution • GENETIC EQULIBRIUM – allele frequencies stay the same from generation to generation – population is NOT evolving 50% white : 50% black 50% white : 50% black 50% BB : 50% bb 50% BB : 50% bb Microevolution • 4 factors that cause microevolution: 1. 2. 3. 4. Gene flow Random Genetic drift Mutation Natural selection Non - random Microevolution • GENE FLOW – Movement of genes into and out of population through immigration and emigration Microevolution • GENETIC DRIFT – Random event wipes out organisms with a particular trait • Leaves behind a changed population • Ex. All green bugs killed in earthquake; all brown left Microevolution • MUTATIONS – Changes in DNA cause changes in adaptations • Genes code for adaptations – Random mutations produce new adaptations Macroevolution • Speciation leads to MACROEVOLUTION – Evolution of new species – SPECIES • Organisms that can interbreed and reproduce Macroevolution • ISOLATION can lead to macroevolution – Inability to mate • 2 types of isolation 1.GEOGRAPHIC 2.REPRODUCTIVE Macroevolution • GEOGRAPHIC ISOLATION – Two populations are separated physically and can’t interbreed • Ex. Distance, barrier – Leads to creation of new species Macroevolution • REPRODUCTIVE ISOLATION – Organisms are separated by reproductive barriers – Not separated geographically • Ex. Different mating dances – Different mating seasons – Mechanical isolation (“Parts don’t fit”) What is the Evidence for Evolution? • Fossil Record • Biogeography • Comparative Anatomy All provide evidence ancestry • Comparative Embryology • Comparative Biochemistry of common Fossils • Fossils may show ancestors of current species – Demonstrates common ancestry and change over time – TRANSITIONAL FOSSILS • Show traits of two groups of organisms; links them together – Ex. Birds & Reptiles Biogeography • Unrelated species have similar traits due to similar environments – Ex. Marsupials & Placentals • Fossils not evenly distributed around the world due to CONTINENTAL DRIFT Comparative Anatomy • Organisms share a common body plan – From a common ancestor – HOMOLOGOUS STRUCTURES • Same structures (bones), different function – Ex. Human arm & dog leg » Bird wing & bat wing – ANALGOUS STRUCTURES • Same function, different structure – NO link to common ancestry » Ex. Bird wing and bug wing Comparative Anatomy • VESTIGIAL STRUCTURE – Found in present day organisms but has no purpose – Functional in ancestor • Ex. Hip bone in whale – Tailbone – Wisdom teeth Comparative Embryology • Early embryos of all vertebrates are very similar – Early development reflects common ancestor Pharyngeal pouches Pharyngeal pouches Tail Tail Fish Reptile Bird Mammal Comparative Biochemistry • All living things use the same basic biological molecules for similar functions – DNA, ATP, amino acids, etc. – Similar molecules have similar biochemical structures Modes of Selection Hunting The Peppered Moth • Pretend you are a bird that preys on peppered moths • Your hunting ground is the side of a tree full of peppered moths • You will be given 1 second to make your choice of quadrant • When a slide comes up, you will decide what quadrant to hunt in • Here are the quadrants… READY? Hunting The Peppered Moth • • • • Which quadrant did you hunt in? Why did you choose this quadrant? How many moths were in this quadrant? How many moths were on the tree? • Prepare to hunt again… • Ready? Hunting The Peppered Moth • • • • Which quadrant did you hunt in? Why did you choose this quadrant? How many moths were in this quadrant? How many moths were on the tree? • Prepare to hunt again… • Ready? Hunting The Peppered Moth • Let’s take a closer look at the first slide • How many moths were in your quadrant? • How many moths are on the tree? Hunting The Peppered Moth • Did you choose the 3rd quadrant? • Did you notice the black moths? • This is how the peppered moth evolved in Manchester England • Now let’s take a look at how the moths changed slowly over time once the trees were polluted Evolution of the Peppered Moth Peppered Moth Simulation • Notice how the white moths were the first to be eaten due to their lack of environmental fitness • Eventually all the white moths were gone and the dark moths prevailed