W09_L8_Natural+Selection

W09_L8_Natural+Selection - Lecture 14: Natural Selection...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Lecture 14: Natural Selection & A Brief History of Evolutionary Thought Realm of Being II. The Evolution of Evolutionary Thought A. Non-evolutionary perspectives NonBeing God Angels Demons Man Realm of Becoming Woman Animals Minerals Man Monkeys Quadrapeds (mammals) Bats Ostrich Birds Aquatic birds Flying fish Whales? Fish Seals? Eels Sea serpents Reptiles Slugs Shellfish Insects Worms Polyps (hydras) Sensitive plants Trees Shrubs Herbs Lichens Mold Minerals Earth Water Air Ethereal matter Early Attempts to Organize Life Scala naturae from Charles Bonnet (circa 1760) Non-Being Non- Rene Descartes 1596-1650 1596Discourse on Method II. The Evolution of Evolutionary Thought A. Non-evolutionary perspectives NonGeorges Cuvier (1769-1832): Paleontologist, anatomist & anti-evolutionist (1769anti History of life in a particular place recorded in fossil beds / strata Age of Enlightenment Hume Franklin Jefferson Malthus Payne Kant Leibniz Adam Smith Modern science of biology II. The Evolution of Evolutionary Thought A. Non-evolutionary perspectives NonHow did Cuvier explain sequential changes of fossils in different rock layers? Revolutions / Catastrophes ("Catastrophism"): (" Catastrophism" Species are immutable All species created separately Boundaries between fossil strata caused by floods, earthquakes, etc. etc. New species appeared in more recent layers by rerepopulating from elsewhere Similarities between organisms reflect a divine plan 2 billion years 1500 meters II. The Evolution of Evolutionary Thought B. The Foundations of the theory Sir Charles Lyell (1797-1875) (1797geological uniformitarianism & gradualism (vs. catastrophism) catastrophism) "The present is the key to the past." past." The Colorado River cut through 2 billion years of rock in 7-15 million years 7- 1 II. The Evolution of Evolutionary Thought B. The Foundations of the theory By the end of the 18th century, these facts were becoming accepted by scientists... scientists... 1. Organisms have changed to some extent over time (evolved) 2. Extinctions are commonplace 3. The earth is OLD (much older than Biblical estimates of 500050009000 years) http://www.mlahanas.de/Greeks/Evolution.htm I. Facts that we now take for granted A. The Earth is old: ____________________ B. The planet has changed since it was formed C. Life has been around for a long time: _________ D. The biological world has changed since life originated E. All life on Earth has descended from a single ancestor F. The degree of resemblance among organisms corresponds to their relatedness G. Resemblance among relatives is due to inheritance of genes: 1. 2. Individuals differ, even close relatives The magnitude of the difference between relatives reflects time since they shared a common ancestor II. The Evolution of Evolutionary Thought B. The Foundations of the theory But some nagging questions persisted... 1. Why do organisms appear to be designed? 2. Where do new species come from? 3. Why do organisms resemble each other, even in their underlying features? Shared ancestry and inheritance (homology) OR a creator's plan? homology) creator' 4. Why do organisms have vestigial structures? Evolutionary relicts (organisms are built on their ancestor's body plans) ancestor' OR an undiscovered function? 5. Why do organisms sometimes seem to be so badly designed? Evolutionary legacy OR a cruel / inept designer or creator? II. The Evolution of Evolutionary Thought C. Pre-Darwinian evolutionary thought PreLamarck's Proposal: Lamarck' 1. Principle of use & disuse ...Disuse leads to vestigial organs 2. Inheritance of acquired characteristics ...through use & disuse Jean-Baptiste de Lamarck (1744-1829) Jean(1744- II. The Evolution of Evolutionary Thought C. Pre-Darwinian evolutionary thought Pre- The more Donkey Kong punches, The bigger his fist gets. Inheritance of acquired characters??? ? 2 III. The Theory of Evolution by Natural Selection A. Charles Robert Darwin Charles Robert Darwin (12 Feb. 1809-19 April 1882) 1809Wanted to be a doctor but ,... ,... He left med school to become an Anglican minister, ... Gave this up to be the naturalist on the HMS Beagle (1831-1836) (1831- III. The Theory of Evolution by Natural Selection A. Charles Robert Darwin It was not an easy journey... Planned for 2, lasted 5 years III. The Theory of Evolution by Natural Selection A. Charles Robert Darwin III. The Theory of Evolution by Natural Selection A. Charles Robert Darwin Darwinian descent with modification: we now represent modification: this fact with a branching phylogenetic diagram On the voyage, Darwin noted the amazing diversity or life across the continents Back home, the Galapagos finch and mockingbird specimens helped lead to the idea of "descent with modification" modification" (evolution as genealogical change) A page from Darwin's Notebook B showing the first evolutionary tree diagram But, what caused modification/adaptation? III. The Theory of Evolution by Natural Selection A. Charles Robert Darwin In 1838, Darwin read Malthus' (1798) Essay on the Principle Malthus' of Population and basically understood the "struggle for existence" and thus Natural Selection existence" He thus began 20 years of work collecting detailed examples to support his theory of evolution by Natural Selection Darwin aimed to show that: "species had not been created separately" separately" "natural selection had been the chief agent of evolutionary change." change." III. The Theory of Evolution by Natural Selection B. Oh Sh*t! Alfred Russel Wallace Sh*t! The crisis of 1857-58: A letter from Alfred Russel Wallace... 1857C. DARWIN to A.R. WALLACE Down, Bromley, Kent, May 1, 1857. My dear Sir,--I am much obliged for your letter of Sir,-- Oct. 10th from Celebes, received a few days ago..., I can plainly see that we have thought much alike and to a certain extent have come to similar conclusions... conclusions... ...I am now preparing my work for ...I publication, but I find the subject so very large, publication, that though I have written many chapters, I do not suppose I shall go to press for two years. Alfred Russel Wallace (1823-1913); photo taken when (1823he was 25 Origin of Species 1st published 150 years ago this year (Nov. 29, 1859) 3 III. The Theory of Evolution by Natural Selection C. Observations leading to the theory Six observations led to three inferences: Observation 1: Populations should increase 1: exponentially if all offspring survived to reproduce (from Malthus) Observation 2: Populations do NOT increase 2: exponentially: they remain at a relatively constant size Observation 3: Limited availability of resources, 3: predation or disease control population size: Most offspring do NOT survive III. The Theory of Evolution by Natural Selection C. Observations leading to the theory Observation 4: The individual members 4: of a species always differ in phenotype Observation 5: Offspring tend to resemble parents; some resemblance is due to inherited factors, and some is due to shared environments INFERENCE 2: The best competitors win in the struggle for existence There are predictable and stable differences in the traits possessed by those who do and those who do not survive in the struggle for existence = DIFFERENTIAL SURVIVAL INFERENCE 1: There is a "struggle" for struggle" existence due to excess fecundity III. The Theory of Evolution by Natural Selection C. Observations leading to the theory Observation 6: New and stable "varieties" with desirable qualities 6: varieties" can be created by artificial selection III. The Theory of Evolution by Natural Selection C. Observations leading to the theory <5,000 years of evolution by artificial selection (gets you broccoli!) Wild "cabbage" cabbage" 14,000 years of evolution by artificial selection (gets you a Chihuahua from a wolf) Chihuahua III. The Theory of Evolution by Natural Selection C. Observations leading to the theory English Carrier Saxon Fairy Swallow III. The Theory of Evolution by Natural Selection C. Observations leading to the theory Observation 6: New and stable "varieties" with desirable qualities 6: varieties" can be created by artificial selection INFERENCE 3: Heritable traits that enhance survival and reproduction in nature will increase in frequency in the population through time English Pouter Indian Faintail Jacobin This is Natural Selection: Selection: As defined in the textbook: "The differential contribution of offspring to the next generation by various genetic types belonging to a population" population" 4 III. The Theory of Evolution by Natural Selection C. Observations leading to the theory Who was the first person to propose a theory to explain evolutionary change in living things? A. Charles Lyell B. Jean-Baptiste de Lamarck JeanC. Charles Darwin D. Alfred Russel Wallace E. both C and D II. The Evolution of Evolutionary Thought B. The Foundations of the theory But some nagging questions persisted... 1. Why do organisms appear to be designed? 2. Where do new species come from? 3. Why do organisms resemble each other, even in their underlying features? Shared ancestry and inheritance (homology) OR a creator's plan? homology) creator' 4. Why do organisms have vestigial structures? Evolutionary relicts (organisms are built on their ancestor's body plans) ancestor' OR an undiscovered function? 5. Why do organisms sometimes seem to be so badly designed? Evolutionary legacy OR a cruel / inept designer or creator? II. The Evolution of Evolutionary Thought B. The Foundations of the theory 1. Why do organisms appear to be designed? II. The Evolution of Evolutionary Thought B. The Foundations of the theory But some nagging questions persisted... 1. Why do organisms appear to be designed? 2. Where do new species come from? 3. Why do organisms resemble each other, even in their underlying features? Shared ancestry and inheritance (homology) OR a creator's plan? homology) creator' 4. Why do organisms have vestigial structures? Evolutionary relicts (organisms are built on their ancestor's body plans) ancestor' OR an undiscovered function? 5. Why do organisms sometimes seem to be so badly designed? Evolutionary legacy OR a cruel / inept designer or creator? We now know the Answer: Natural Answer: selection allows adaptations to succeed II. The Evolution of Evolutionary Thought B. The Foundations of the theory 2. Where do new species come from? II. The Evolution of Evolutionary Thought B. The Foundations of the theory But some nagging questions persisted... 1. Why do organisms appear to be designed? 2. Where do new species come from? 3. Why do organisms resemble each other, even in their underlying features? Shared ancestry and inheritance (homology) OR a creator's plan? homology) creator' 4. Why do organisms have vestigial structures? Evolutionary relicts (organisms are built on their ancestor's body plans) ancestor' OR an undiscovered function? 5. Why do organisms sometimes seem to be so badly designed? Evolutionary legacy OR a cruel / inept designer or creator? Answer: New Answer: species evolve from other species through speciation 5 II. The Evolution of Evolutionary Thought B. The Foundations of the theory 3. Why the resemblances among organisms? II. The Evolution of Evolutionary Thought B. The Foundations of the theory But some nagging questions persisted... 1. Why do organisms appear to be designed? 2. Where do new species come from? 3. Why do organisms resemble each other, even in their underlying features? Shared ancestry and inheritance (homology) OR a creator's plan? homology) creator' 4. Why do organisms have vestigial structures? Evolutionary relicts (organisms are built on their ancestor's body plans) ancestor' OR an undiscovered function? 5. Why do organisms sometimes seem to be so badly designed? Evolutionary legacy OR a cruel / inept designer or creator? Answer: Inheritance from a common ancestor = HOMOLOGY Answer: II. The Evolution of Evolutionary Thought B. The Foundations of the theory 4. Vestigial organs: why do organisms have them? II. The Evolution of Evolutionary Thought B. The Foundations of the theory 4. Vestigial organs: why do organisms have them? Vestigial hindlimbs in whales Vestigial hindlimbs in boas and pythons II. The Evolution of Evolutionary Thought B. The Foundations of the theory 4. Vestigial organs: why do organisms have them? Ear muscles II. The Evolution of Evolutionary Thought B. The Foundations of the theory But some nagging questions persisted... 1. Why do organisms appear to be designed? 2. Where do new species come from? 3. Why do organisms resemble each other, even in their underlying features? Shared ancestry and inheritance (homology) OR a creator's plan? homology) creator' 4. Why do organisms have vestigial structures? Evolutionary relicts (organisms are built on their ancestor's body plans) ancestor' OR an undiscovered function? This is another example of apparently "bad design" design" Vermiform appendix 5. Why do organisms sometimes seem to be so badly designed? Evolutionary legacy OR a cruel / inept designer or creator? Answer: historical baggage/evolutionary legacy Answer: 6 II. The Evolution of Evolutionary Thought B. The Foundations of the theory 5. Why do some things appear to be designed poorly? II. The Evolution of Evolutionary Thought B. The Foundations of the theory But some nagging questions persisted... 1. Why do organisms appear to be designed? 2. Where do new species come from? 3. Why do organisms resemble each other, even in their great theories of science because underlying features? Shared ancestry and inheritance it answers so many disparate and (homology) OR a creator's plan? homology) creator' 4. Why do organisms haveof principles; it simple set vestigial structures? Evolutionary relicts (organisms are built on their ancestor's body plans) ancestor' provides a unifying structure to all OR an undiscovered function? Answer: Selection works on historical contingency / pre-existing traits; and presometimes tradeoffs lead to imperfect solutions Darwin's theory of evolution by Darwin' natural selection is one of the fundamental questions with a 5. Why do organisms sometimes seem to be so badly designed? Evolutionary legacy OR A cruel designer or creator? of biology III. The Theory of Evolution by Natural Selection D. Formal statement of the theory of NS A formal statement of the conditions for natural selection: 1. Individuals must reproduce to form the next generation 2. Individuals within a population must vary in phenotype 3. Individuals pass on at least some of their traits to their offspring (inheritance) (inheritance) 4. Individuals with different traits have differential survival or reproductive success during the struggle for existence III. The Theory of Evolution by Natural Selection D. Formal statement of the theory of NS Natural Selection leads to ADAPTATIONS: ADAPTATIONS: An adaptation is a a trait that increases an organism's organism' survival or reproductive success (a noun) noun) Adaptation also refers to the process by which a beneficial trait (i.e. an adaptation) spreads in a population (i.e. evolves by natural selection) We measure increased survival / reproduction as FITNESS: The number of offspring that survive and reproduce (i.e. the contribution of genes to the next generation); often measured by proxies; relative fitness is key Traits that are heritable and that enhance survival and/or reproduction relative to other members of the population will increase in frequency from generation-to-generation, generation- toso long as a particular selective regime persists III. The Theory of Evolution by Natural Selection D. Formal statement of the theory of NS Natural selection ... ... is a process by which "design" (i.e. adaptations) can emerge without design" requiring a conscious designer. It Is a materialistic explanation for the complexity of life on earth a radical idea! ... acts on phenotypes, and thus indirectly on genotypes. What does this mean? ... Acts on the individual, but leads to evolution in populations, not individual, populations, individuals ... Is a scientific "theory", not just a "hypothesis" hypothesis" theory" Theory = A testable model of the manner of interaction of a set of natural phenomena, capable of predicting future occurrences or observations of the same kind, and capable of being tested through through experiment or otherwise verified through empirical observation Hypothesis = a suggested explanation for a phenomenon III. The Theory of Evolution by Natural Selection E. Things that were hard for Darwin to explain... In Darwin's day, they believed in Blending Inheritance Darwin' Problem: Eventually, the population should become Problem: phenotypically uniform. So much for selection... P1 Father x Mother Offspring Offspring Offspring F1 Mendel to the rescue! 7 III. The Theory of Evolution by Natural Selection E. Things that were hard for Darwin to explain... Other things that Darwin had a hard time explaining at first (but which he or others later explained)... Gaudy Animals... Cooperation... 8 ...
View Full Document

Ask a homework question - tutors are online