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Transcript
Theory of Evolution & Natural Selection Theory • In science, theories are statements or models that are used to support facts. • Theories have some important properties: – They explain a wide variety of data and observations – They can be used to make predictions – They are not absolute, they serve as a model of understanding the world and can be changed as the world view changes The theory of evolution remains one of the most useful theories in biology because it explains many questions and observations. Some questions that can be answered by evolution. • Why do so many different animals have the same structures, the arm bones in a human are the same bones as a flipper in a whale? • Why do organisms have structures they no longer use, like the appendix in a human? Non functioning wings in penguins • Why are there bones and fossil evidence of creatures that no longer exist? What happened to these creatures? • Why do so many organisms' morphology and anatomy follow the same plan? • Why is the sequence of DNA very similar in some groups of organisms but not in others? • Why do the embryos of animals look very similar at an early stage? Evolution • Evolution = change over time Evolution of Species • The change in a population of organisms over time caused by both genetic change and environmental factors. History of Evolutionary Thought copyright cmassengale 7 Early Ideas On Earth’s Organisms • Aristotle believed species were fixed creations arranged by their complexity • Idea lasted 2000 years copyright cmassengale 8 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 9 Lamarck • Jean-Baptiste Pierre Antoine de Monet, Chevalier de la Marck (1744 - 1829), often just known as "Lamarck.” • Naturalist who lived before and during Darwin’s lifetime Lamarck • Ideas that were proven to be untrue – Traits evolved through use or disuse (Ex. neck of giraffe, wings of a penguin) – Traits acquired over an individual's lifetime could be passed down to its offspring (Ex. Bodybuilder) • Ideas that Darwin built upon – Evolutionary change takes place gradually and constantly Lamarck’s Theory of Evolution • Jean-Baptiste Lamarck, 1809 • One Of First Scientists To Understand That Change Occurs Over Time • Stated that Changes Are Adaptations To Environment acquired in an organism’s lifetime and passed to offspring copyright cmassengale 12 Lamarck’s Theory of Evolution • Idea called Law of Use and Disuse • If a body part were used, it got stronger • If body part NOT used, it deteriorated copyright cmassengale 13 copyright cmassengale 14 Lamarck’s Mistakes • Lamarck Did NOT Know how traits were inherited (Traits are passed through genes) • Genes Are NOT Changed By Activities In Life • Change Through Mutation Occurs Before An Organism Is Born copyright cmassengale 15 Lamarck’s Theory of Evolution • Inheritance Of Acquired Traits – Traits Acquired During Ones Lifetime Would Be Passed To Offspring Clipped ears of dogs could be passed to offspring! 16 Charles Darwin the Naturalist copyright cmassengale 17 Charles Darwin • • • • 1809 – 1882 Born in England Biologist & Naturalist Explored Galapagos Islands on the HMS Beagle • Wrote On the Origin of Species Darwin’s Voyage of Discovery A reconstruction of the HMS Beagle sailing off Patagonia. copyright cmassengale 19 Darwin Left England in 1831 Darwin returned years later in 1836 copyright 5 cmassengale 20 HMS Beagle’s Voyage copyright cmassengale 21 The Galapagos Islands • Small Group of Islands 1000 km West of South America • Very Different Climates • Animals On Islands Unique • Tortoises • Iguanas • Finches copyright cmassengale 22 Galapagos Islands • Vast number of endemic species, found only on the islands copyright cmassengale 24 copyright cmassengale 25 Darwin’s Observations & Conclusions The Struggle for Existence copyright cmassengale 26 Voyage of the Beagle During His Travels, Darwin Made Numerous Observations And Collected Evidence That Led Him To Propose A Revolutionary Theory About The Way Life Changes Over Time copyright cmassengale 27 Darwin’s Observations • Patterns of Diversity were shown • Unique Adaptations in organisms • Species Not Evenly Distributed copyright cmassengale 28 Adaptation • Process where a population becomes better suited to its environment This process takes place over many generations. • May also refer to a feature which is especially important for an organism's survival. Definition • Evolution is the slow , gradual change in a population of organisms over time copyright cmassengale 30 Darwin’s Conclusion • If there are more individuals than can be supported by the environment there will be a struggle for existence among individuals • Only a fraction of the offspring survive each generation copyright cmassengale 31 Darwin’s Observations • Individuals of a population vary in their characteristics with no two individuals being exactly alike. • Much of this variation between individuals is genetically inheritable. copyright cmassengale 32 Darwin’s Conclusion • Individuals who inherit characteristics most fit for their environment are likely to leave more offspring than less fit individuals • Called Natural Selection copyright cmassengale 33 Natural Selection • Survival of the Fittest • Fitness = ability to survive • Darwin’s theory that life forms better adapted to their current environment have a better chance of surviving and will pass on their traits to their offspring • Natural selection -> Evolution Darwin Presents His Ideas to the public On the Origin of Species published in 1859 copyright cmassengale 36 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 Almost 25 Years – Why? copyright cmassengale 37 Publication of “On The Origin of Species” • Darwin Knew That His Theory Would Be Extremely Controversial And Would Be Attacked • His Theory Challenged Popular Beliefs copyright cmassengale 38 Publication of “On The Origin of Species” • Darwin read an Essay From Alfred Wallace – Fellow Naturalist – Independently Developed The Same Theory 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 39 5 Major of Points of Darwin’s Theory of Evolution by Natural Selection 1. Populations have Variations 2. Some Variations are favorable What type of finch would be most fit to live in an area with many seeds available to eat? 3. More offspring are produced than survive If more offspring die than are produced this eventually will result in extinction, when a species no longer exists 4. Those that survive have favorable traits (the most fit) Peppered Moths 5. Populations will change over time Common 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 copyright cmassengale 46 Theory of Evolution Supporting Evidence copyright cmassengale 47 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 – Homologous Structures of Living Organisms – Similarities In Early Development copyright cmassengale 48 Evidence to Support Evolution & Natural Selection • Comparative Anatomy • Geology & Fossils • DNA research Comparative Anatomy • Study of similarities and differences in the anatomy (structure) of different organisms. • Indicates that various organisms share a common ancestor. Homologous Structures • Features of organisms that may not perform the same function but share similar anatomy. Homologous Structures copyright cmassengale 52 Embryology • The study of developing organisms • Embryo – early stages of vertebrate development Similarities In Early Development • Embryonic Structures Of Different Species Show Significant Similarities copyright cmassengale 54 Ex. Similarities of chordates • 1. Pharyngeal slits • 2. Notochord 3. Dorsal, hollow nerve cord 4. Posterior elongation of body Evidence for Evolution - Comparative Embryology Similarities In Embryonic Development copyright cmassengale 56 Geological & Fossil Evidence • By comparing layers of rock from different parts of the world, the sequence from the very earliest life to the present can be observed in fossils, in this way the fossil record shows a change from simple to complex organisms. DNA evidence • DNA in every organism shares the same amino acid base pairs – (A/T, C/G) • Different amount of pairs • Different sequence of pairs Phylogenic Tree • Life forms have evolved from simple organisms in oceans through amphibians to higher forms such as primates. Common 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 copyright cmassengale 60 Common Ancestor • An organism or group of organisms to which two or more species can trace their history Phylogenic Tree • Life forms have evolved from simple organisms in oceans through amphibians to higher forms such as primates. Modern Evolutionary Concepts Gene Pool • All of the alleles (genes) in a population of species • Also called allele frequency Genetic Drift • Change in the frequency of alleles in a population’s gene pool through mutation, reproductive isolation, or chance Mutation • A change in DNA, usually results from a mistake during mitosis • Can be helpful, harmful or have no effect on an organism Reproductive Isolation • What is Isolation? • Reproductive Isolation = Processes or behaviors that prevent a species from reproducing – 3 Types Temporal Isolation • When timing does not allow for reproduction • Ex. Winter vs. Summer Rabbits Behavioral Isolation • Different mating rituals Geographic Isolation • Organisms are separated by land or water features Speciation • New species can develop when part of the population becomes separated and evolves in isolation. Founder Effect • Loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. Bottleneck Effect • Reduction in size and genetic variation in size of a population due to natural disasters, disease or predators. Biodiversity • Evolution & Natural Selection can lead to biodiversity • Biodiversity = Variety of species living in the same habitat or environment Benefits of Biodiversity • • • • Reduces competition Helps to cycle nutrients and waste Medicine & Food Industry & Leisure