Darwin's Evolution Notes - PDF

Evolution Diversity of Life 1  Evolution “Nothing in biology makes sense EXCEPT in the light of evolution.” Theodosius Dobzhansky Charles Darwin in later years 2  History of Evolutionary Th...

Evolution Diversity of Life 1  Evolution “Nothing in biology makes sense EXCEPT in the light of evolution.” Theodosius Dobzhansky Charles Darwin in later years 2  History of Evolutionary Thought 3  Early Ideas On Earth’s Organisms Aristotle believed species were fixed creations arranged by their complexity Idea lasted 2000 years 4  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 5 6  Catastrophism Idea proposed by George Cuvier Studied fossil in sedimentary rock strata of Paris Found some species completely disappeared in more recent layers 7  Catastrophism Stated that species disappear due to a catastrophic event of the earth’s crust (volcano, earthquake…) 8  Hutton’s Theory of Geological Change James Hutton, 1795, Scottish geologist Studied invertebrate fossils in Paris Museum Described The Geological Forces That Have Changed Life on Earth Over Millions of Years (erosion, earthquakes, volcanoes…) 9  Hutton’s Theory of Geological Change Changes in Earth’s crust due to slow continuous processes Idea Known as Gradualism 10  Charles Lyell Proposed theory of Uniformintarianism Geological processes at uniform rates building & wearing down Earth’s crust Proposed that the Earth was millions of years instead of a few thousand years old 11  Principles of Geology Published by Lyell Just Before The Beagle Set Sail & read by Darwin Explained Geological Processes That Shaped The Earth Helped Darwin Understand Sea Shells In The Andes Mountains At 12,000+ Feet – Expanded Earth’s Age 12  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 Said acquired changes were passed to offspring 13  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 14  Lamarck’s Theory of Evolution Inheritance of Acquired Characteristics Proposed That By Selective Use Or Disuse Of Organs, Organisms Acquired Or Lost Certain Traits During Their Lifetime These Traits Could Then Be Passed On To Their Offspring Over Time This Led To New Species 15  Lamarck’s Theory of Evolution Use & Disuse - Organisms Could Change The Size Or Shape Of Organs By Using Them Or Not Using Them Blacksmiths & Their Sons (muscular arms) Giraffe’s Necks Longer from stretching) 16 copyright cmassengale 17  Lamarck’s Theory of Evolution Inheritance Of Acquired Traits – Traits Acquired During Ones Lifetime Would Be Passed To Offspring 18 Clipped ears of dogs could be passed to offspring!  Lamarck’s Theory of Evolution Tendency Toward Perfection Organisms Are Continually Changing and Acquiring Features That Help Them Live More Successfully In Their Environment Example: Bird Ancestors Desired To Fly So They Tried Until Wings Developed c 19  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 20 Evolutionary Timeline 21 Charles Darwin the Naturalist 22  Voyage of the Beagle Charles Darwin Born Feb. 12, 1809 Joined Crew of HMS Beagle, 1831 Naturalist 5 Year Voyage around world Avid Collector of Flora & Fauna Astounded By Variety of Life 23  Darwin’s Voyage of Discovery A reconstruction of the HMS Beagle sailing off Patagonia. 24 Darwin Left England in 1831 Darwin returned 5 years later in 1836 25 HMS Beagle’s Voyage 26  The Galapagos Islands Small Group of Islands 1000 km West of South America Very Different Climates Animals On Islands Unique »Tortoises »Iguanas »Finches 27  The Galapagos Islands Volcanic islands off the coast of South America Island species varied from mainland species & from island-to-island species Each island had long or short neck 28 29  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 30 31 Darwin’s Observations & Conclusions The Struggle for Existence 32  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 33  Darwin’s Observations Patterns of Diversity were shown Unique Adaptations in organisms Species Not Evenly Distributed » Australia, Kangaroos, but No Rabbits » S. America, Llamas 34  Darwin’s Observations Both Living Organisms & Fossils collected Fossils included: »Trilobites »Giant Ground Sloth of South America This species NO longer existed. What had happened to them? 35 Evidence for Evolution – The Fossil Record 36  Definition Evolution is the slow , gradual change in a population of organisms over time 37  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 38  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 39  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. 40  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 41 Darwin’s Theory of Evolution The unequal ability of individuals to survive and reproduce leads to a gradual change in a population, with favorable characteristics accumulating over generations (natural selection) New species evolve 42 Ideas That Shaped Darwin’s Thinking Thomas Malthus 43  Contributor’s to Darwin’s : thinking included: Charles Lyell –uniformintarianism (geologic processes still changing Earth) Georges Cuvier – species extinction (Catastrophism) Thomas Malthus – struggle for existence (resources) 44  Contributor’s to Darwin’s thinking included: : James Hutton - Gradualism John Baptiste Lamarck – Inheritance of acquired Characteristics and Law of Use and Disuse Alfred Russel Wallace – organisms evolved from common ancestors 45  Population Growth Thomas Malthus, 1798 Economist Observed Babies Being Born Faster Than People Were Dying Population size limited by resources such as the Food Supply 46 The Struggle for Existence Malthus’ Influence: – High Birth Rates & Limited Resources Would Force Life & Death Competition Each Species Struggles For: – Food – Living Space – Mates 47  Population Growth Malthus Reasoned That If The Human Population Continued To Grow Unchecked, Sooner or Later There Would Be Insufficient Living Space & Food For Everyone Death Rate Will Increase To Balance Population size & Food Supply 48  Population Growth Darwin Realized Malthus’s Principles Were Visible In Nature Plants & Animals Produce Far More Offspring Than Can Be Supported – Most Die – If They Didn’t – Earth Would Be Overrun 49 Darwin’s Theory of Evolution Organisms Change Over Time 50  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 51  Natural Selection Driving force for evolution During the struggle for resources, strongest survive & reproduce Idea that at least some of the differences between individuals, which impact their survival and fertility, are inheritable. 52 Origin of Species Darwin Presents His Case 53  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? 54  Publication of “On The Origin of Species” Darwin Knew That His Theory Would Be Extremely Controversial And Would Be Attacked His Theory Challenged Established Religious & Scientific Beliefs, Particularly About The Creation Of Man 55  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 56  Wallace’s Contribution Alfred Russel 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 57  Publication of “On The Origin of Species” Darwin Presented Wallace’s Essay & Some Of His Work At A Scientific Conference of the Linnaean Society in July of 1858 Then He Started On his book “Origin of Species” It Took Darwin 18 Months To Complete The Book 58  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 59  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 60  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 61 62 Origin of Species Concepts and Controversy 63 Descent With Modification Takes Place Over Long Periods of Time Natural Selection Can Be Observed As Changes In – Body Structures – Ecological Niches – Habitats 64 Descent With Modification Species Today Look Different From Their Ancestors Each Living Species Has – Descended – With Changes – From Other Species – Over Time 65 Descent With Modification 66  Descent With Modification Implies – All Living Organisms Are Related – Single Tree of Life »DNA, Body Structures, Energy Sources Common Descent – All Species, Living & Extinct, Were Derived From Common Ancestors 67  Major Problem in Darwin’s Theory No mechanism to explain natural selection How could favorable variations be transmitted to later generations? With the rediscovery of Mendel’s work in the first half of the 20th century, the missing link in evolutionary theory was. found 68  Opposition to Evolution The upheaval surrounding evolution began with Darwin’s publication of On the Origin of Species By Means of Natural Selection The debate continues nearly 150 years later 69 Theory of Evolution Today Supporting Evidence 70  Homologous Body Structures Structures That Have Different Mature Forms But Develop From The Same Embryonic Tissues Strong Evidence That All Four-Limbed Animals With Backbones Descended, With Modification, From A Common Ancestor Help Scientist Group Animals 71 Homologous Structures 72  Homologous Body Structures Not All Serve Important Functions – Vestigial Organs » Wisdom Teeth » Tailbone 73  Fossil Record Earth is Billions of Years Old Fossils In Different Layers of Rock (sedimentary Rock Strata) Showed Evidence Of Gradual Change Over Time 74  75 Similarities in DNA Sequence  Evolution of pesticide resistance in response to selection 76 Evidence for Evolution – Evolution Observed Evolution of drug-resistance in HIV 77  Geographic Distribution of Living Species Different Animals In Different Locations But Share a Common Ancestor Ex. Darwin’s Finches from South America and spreading to nearby islands and evolving fast (adaptive radiation) 78  Similarities In Early Development Embryonic Structures Of Different Species Show Significant Similarities Embryo – early stages of vertebrate development 79  Evidence for Evolution - Comparative Embryology Similarities In Embryonic Development 80 Human Fetus – 5 weeks 81 Chicken Turtle Rat 82  Evidence of Evolution Key Concept 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 83 Review 84  Darwin's Theory 1. Individual Organisms In Nature Differ From One Another. Some Of This Variation Is Inherited 2. Organisms In Nature Produce More Offspring Than Can Survive, And Many Of These Offspring Do No Reproduce 85  Darwin's Theory 3. Because More Organisms Are Produced Than Can Survive, Members Of Each Species Must Compete For Limited Resources 4. Because Each Organism Is Unique, Each Has Different Advantages & Disadvantages In The Struggle For Existence 86  Darwin's Theory 5. Individuals Best Suited To Their Environment Survive & Reproduce Successfully – Passing Their Traits To Their Offspring. 6. Species Change Over Time. Over Long Periods, Natural Selection Causes Changes That May Eventually Lead To New Species 87  Darwin's Theory 7. Species Alive Today Have Descended With Modifications From Species That Lived In The Past 8. All Organisms On Earth Are United Into A Single Tree Of Life By Common Descent 88 Factors that Influence Speciation Mutation Migration Natural Selection Genetic Drift– Frequency when Alleles show up (due to chance) 89  Natural Selection The process where species adapt to their environment. 90 Evolution By Natural Selection Concepts Variation (Species are different from each other) The Struggle for Existence (compete for food, mates, space, water, etc.) Survival of the Fittest (strongest able to survive and reproduce) Descent with Modification (new species arise from common ancestor replacing less fit species) 91  Natural Selection Variation: Genetic or Phenotypic differences within a species 92  Survival of the Fittest Fitness – Ability of an Individual To Survive & Reproduce Adaptation – Inherited Characteristic That Increases an Organisms Chance for Survival 93  Survival of the Fittest Adaptations Can Be: – Physical »Speed, Camouflage, Claws, Quills, etc. – Behavioral »Solitary, Herds, Packs, Activity, etc. 94  Survival of the Fittest Fitness Is Central To The Process Of Evolution Individuals With Low Fitness – Die – Produce Few Offspring Survival of the Fittest AKA Natural Selection 95  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 96  Natural Selection Cannot Be Seen Directly It Can Only Be Observed As Changes In A Population Over Many Successive Generations – Radiation – Fossil Record 97 Types of Natural Selection Directional Stabilizing Disruptive Sexual Selection* 98  Natural Selection Individuals do not evolve; populations do What would happen if a white peppered moths and sooty peppered moths were isolated from each other? 99 100 101 102 103 104 105 106 107  Sexual Selection Natural selection arising through preference by one sex for certain characteristics in individuals of the other sex. 108 109  Genetic Drift Changes to Allele Frequencies due to random chance Two types of Genetic Drift Founder Effect Bottleneck Effect 110 Founder Effect 111 Bottleneck Effect 112 Evolutionary Time Scales Microevolution: Short time scale events (generation-to-gen eration) that change the genotypes and phenotypes of 113 populations  Evolutionary Time Scales Macroevolution: Long time scale events that create and destroy species. 114  DISCUSS! In your opinion, what would be a better evolutionary strategy: being well- adapted to a single environment and food source, or having very diverse adaptations? Explain. 115