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Intro “There is no ‘Great Plan’ out there to conform with the evolutionary theory, just organisms struggling to pass their genes on to the next generation. That’s it” Evolution • Changes in groups of organisms over time History of Evolution Important Players James Hutton • Published studies in 1785 • Geologist • Theory of Uniformity- the earth was created by the same forces that are in existence today (plate tectonics) • Before Hutton, world was thought to be 6000 years old • His research supported that the Earth is 4.6 billions years old Thomas Malthus • Worked with human population studies • Observed that plants and animals reproduce at a greater rate than their ability for survival, creating competition within a species • Important to Wallace and Darwin’s theory Jean-Baptiste Lamarck 1809- 1st to develop a scientific theory of evolution known as the Theory of Inheritance of Acquired Characteristics: Organisms developed new organs or modified old ones to meet environmental challenges Selective use or disuse would alter the size or shape of organs or structures passed to offspring Examples Larmarck Observed • Long Neck giraffes - short neck giraffes that strained to reach higher branches would grow longer necks Lamarck’s Theory Proven to be False • Change DNA by usage of the structures (BOGUS! Mendel was not yet born so little was known about genetics). Think of body building and passing that on to your offspring • No extinction of species, just changed into other organisms • Lower order organisms were spontaneously created to fill the void (nothing was due to chance). Alfred Wallace • 1850’s • Naturalist • Developed a theory similar to Darwin’s • His essay to Darwin motivated Darwin to publish the book, On the Origin of Species. Letter from Wallace to Darwin in 1864 “I shall always maintain (the theory of evolution by natural selection) to be actually yours and yours only. You had worked it out in details I had never thought of years before I had a ray of light on the subject” Charles Darwin • 1830’s • Known as the “Father of Evolution” • Naturalist on the HMS Beagle (shipping vessel) collecting specimens and created detailed written observations • Inspired by the biological diversity of the Galapagos Islands Voyage of the Beagle • 5 year voyage began in 1831 • Only 5 weeks spent on the Galapagos Islands • Saw variations of organisms on the different islands (thought that this could be modification due to environment) – Ex. Finches – beaks shape varied – Ex. Tortoises – neck length varied Support for Evolution 1) Fossil Record 2) Comparative Anatomy 3) Comparative Embryology 4) Comparative Biochemistry 5) Geographic Distribution 1) Fossil Record • Offers some of the most significant evidence of evolutionary change • Determines ancestry of organisms • Reveals patterns of evolution Whole organism Cast fossil Archaeopteryx – earliest bird (had reptilian and bird –like characteristics **It was only 50 centimeters from wingtip to wingtip (about 19 inches) 2) Comparative Anatomy • Homologous Structures – same structure, different function (inherited from common ancestor) • Analogous Structures – different structure, same function (not inherited from common ancestor) • Vestigial Structures – reduced forms of functional structures Vestigial Organ 3) Comparative Embryology • Shows evolutionary relationships 4) Comparative Biochemistry • More similar DNA, more similar the organisms (remember DNARNAprotein – made of amino acids) 5) Geographic Distribution • Animals that live close together are more closely related than those that are geographically separated South American Mara English Rabbit How do the following support the theory of evolution? 1) Fossil Record 2) Comparative Anatomy 3) Comparative Embryology 4) Comparative Biochemistry 5) Geographic Distribution Adaptation • While Darwin used all of the previous support for Evolution (except Biochemistry), the concept of adaptation is at the heart of his theory Adaptation • Fitness –The more an organism “fits” into its environment, the longer it will survive, the more offspring it will have, and it’s genes will be passed on to the following generations Adaptation • Camouflage – blend to environment Adaptation Can Cause Variation in a Population West African giraffe Reticulated giraffe Thornicroft’s giraffe Adaptation • Mimicry – one species evolves to resemble another species Monarch tastes bad Mechanisms of Evolution • Population Genetics Hardy-Weinberg Principle – states that a population can be in equilibrium if forces do not cause the population to change (very rare!) –The following slides will discuss the ways a population can change Genetic Drift • Any change in a population due to chance • Includes: – Founder Effect – Bottle Neck – Gene Flow – Non-random mating – Mutation – Natural Selection Founder Effect • When a small group of a population moves to another area –These “invaders” rarely have a complete sample of the genes from the larger population –Therefore, the new generation will have less genetic diversity than the original population Dunkers of Eastern Pennsylvania Protestant sect that fled Germany to avoid religious persecution Only married within their sect In Germany, 45% of people had type A blood In the U.S., 40% of people had type A blood In the new Dunker population, 60% of people had type A blood Bottleneck Effect • Occurs when populations are depleted. Even if populations are restored, they will only have remnant of the original gene pool. – Ex. Cheetahs due to ice age 10,000 yrs ago – Ex. Elephant seals due to hunting Gene Flow • Movement of individuals in or out of a population will change the available genes Nonrandom Mating • Individuals can only mate with those nearby • This narrows the gene pool Mutation • Random change in DNA causes changes in traits • Provides the “catalyst” for natural selection to occur Natural Selection • Process in which organisms with favorable traits (traits well suited for their environment) are more likely to survive and reproduce Survival of the Fittest or the “Sexiest” Why are brown beetles more abundant in a population? • Imagine that green beetles are easier for birds to spot (and hence, eat). • Brown beetles are a little more likely to survive to produce offspring. They pass their genes for brown coloration on to their offspring. • So in the next generation, brown beetles are more common than in the previous generation. Why? Show Two Minute Video “Why Sex?” http://www.pbs.org/wgbh/evolution/sex/index.html 4 Ways Natural Selection Can Change a Population 1) Stabilizing Selection – extremes are selected against, typical in organisms that have changed little over millions of years 3) Directional Selection – an extreme is selected Ex. Peppered Moth and industrial revolution Investigation from Arkive • Read the handout Natural selection – the peppered moth Pale coloured, speckled peppered moth Natural selection – the peppered moth Dark coloured peppered moth Natural selection – the peppered moth Peppered moths on tree trunk 2) Disruptive selection – selects against intermediate forms and produces two subpopulations Ex. White vs. black snails • White snails will not be easy prey on sand but easily spotted on rocks or dark algae • Black snails will not be easy prey on rocks but easily spotted on sand • Intermediates (brown) are easy prey in either area 4) Sexual Selection – males and females differ in their appearance with males typically more “flashy” to attract more females Speciation • Sometimes gene changes become so great that new species are formed • 2 types: –Allopatric Speciation – new species are created due to geographic isolation –Sympatric Speciation – new species are created due to changes in behavior (food source, mating rituals) Allopatric Speciation Patterns of Evolution 1) Adaptive (Divergent) Radiation 2) Convergent Evolution 3) Coevolution 4) Rate of Speciation Adaptive (Divergent) Radiation • New species evolve from a common ancestor • Revealed by homologous structures Convergent Evolution • Process by which unrelated organisms come to look a like because of similar environment • Analogous structures Coevolution • Two species that evolve together because of their close interaction Rate of Speciation • Gradualism – evolutionary changes occur steadily over time • Punctuated Equilibrium – Long period of time of stasis, short periods of change Review • Describe: – Founder Effect – Bottle Neck – Gene Flow – Non-random mating – Mutation – Natural Selection (We will go over this orally…..you already wrote this in your notes) Review • Describe the 4 ways that natural selection can change a population • Describe the 2 types of speciation • Describe the 4 patterns of evolution • Describe the 2 rates of speciation Animation • Evolution