3 Darwin’s FindingsAfter Darwin returned to England in 1836 he filled notebooks with his ideas about species diversity and the process that he would later call evolution.He did not rush to publish his ideas because they disagreed with the fundamental scientific beliefs of his day.He asked his wife to publish his ideas when he died.Play video
4 Wallace’s EssayIn 1858, another naturalist, Alfred Russell Wallace wrote an essay describing his work in Malaysia that summarized the same ideas Darwin had been thinking about for 25 years.
5 Origin of SpeciesSuddenly Darwin had incentive to publish the results of his work.In 1859 On the Origin of Species presented evidence and proposed a mechanism for evolution that he called natural selection.
6 Evolution is a THEORYA theory is a well-supported, testable explanation of phenomena that have occurred in the natural world, like the theory of gravitational attraction, cell theory, or atomic theory.
7 Keys to Darwin’s Theory Genetic variation is found naturally in all populations.
8 Keys to Darwin’s Theory Struggle for existence means that members of each species must compete for food, space, and other resources.
9 Keys to Darwin’s Theory Some organisms in a population are less likely to survive.
10 Keys to Darwin’s Theory Survival of the fittest organisms which are better adapted to the environment will survive and reproduce, passing on their genes.
11 VocabularyAbility of an individual to survive and reproduce in its specific environment = fitness.Hmmm…
12 VocabularyAny inherited characteristic that increases an organism’s chance of survival = adaptation.
13 What is Darwin’s Theory? Over time, natural selection results in changes in the inherited characteristics of a population.These changes increase a species’ fitness in their environment.How does it work?Descent with modification suggests that each species has descended with changes, from other species over time.This idea suggests that all living species are related to each other; and that all species, living and extinct, share a common ancestor.
14 Evidence of Evolution Artificial selection Fossil record Geographic distributionHomologous structuresEmbryologyDNAVisual record natural selection happening
15 Artificial SelectionIn artificial selection, nature provides the variation through mutation and sexual reproduction; and humans select those traits that they find important.Examples: cows bred to produce more milk; turkeys with more breast meat, etc.
16 Dogs: Artificial Selection Saint Bernard – bred by monks around 1050 A.D. to rescue travelers of mountain passes in the Swiss Alps between Italy and SwitzerlandChihuahua – bred from Techichi of Mexico by Mayans, had religious significance.Dachshund – bred in Germany as earlyas the 15th century to hunt badgers.
18 Proof of EvolutionFossil Record – Fossils are the remains of ancient organisms found in layers of rock in the Earth.
19 Proof of EvolutionThe layers of rock tell the history of the Earth, while the fossils found within the rock tell a history of life.The fossils are thought to be the same age as the rock they are found in.
20 Movement of Earth’s Crust Earthquakes and volcanoes cause uplifting of the layers of the Earth, taking the fossils along.Sea LevelSedimentary rocks form in horizontal layers.When part of Earth’s crust is compressed, a bend in a rock forms, tilting the rock layers.As the surface erodes due to water, wind, waves, or glaciers, the older rock surface is exposed.Fish die inthe oceanand arecovered insediment.Over timeand underincreasingpressure,the remainsbecomesfossilizedFossils ofmarinefish foundon the mountainsides ofsouthwestWyoming,which atone timewascoveredby aninland sea
22 Verifying Darwin’s Findings If Darwin’s theory is correct, one would expect to find closely related yet different species living in a geographic region as they spread into nearby habitats and evolve…Tortoises adapted to different habitats as they spread from the mainland to the different islands. = Divergent Evolution = Adaptive Radiation.
23 Adaptive Radiation Intermediate vegetation Intermediate necks Little vegetation Long necksLots of vegetation Short necks
24 Adaptive RadiationThe beaks of Galapagos finches have adapted to eating a variety of foods.
25 Verifying Darwin’s Findings If Darwin’s theory is correct you would also expect to find different species living far apart in geographic regions with similar habitats becoming more alike as they adapt to similar ecosystems.Whales and sharks have a similar body design even though they are very different organisms (one is a fish; the other, a mammal) because they have independently adapted to living in a similar environment = Convergent Evolution.
26 Geographic Distribution Beaver and capybaraare closely-related species living in very different environments,while beaver and musk-rat are distantly-related species living in a similar environment.Differences betweenbeaver and capybarashow divergent evolution, whilesimilaritiesbetween beaver andmuskrat show convergent evolution.Differences between closely-related muskratand coypu show divergent evolution, while similaritiesbetween distantly-related capybaraand coypu show convergent evolution.BeaverNORTH AMERICAMuskratCapybaraSOUTH AMERICACoypuBeaver and MuskratCoypu and Capybara
27 Homologous Structures Structures, like the limbs of vertebrates, look very different, but are made from the same bones, because they are made from the same clump of undifferentiated cells in the embryo.
28 Homologous Structures TurtleAlligatorBirdMammalAncient lobe-finned fish
29 Homologous Body Structures Some homologous body structures are vestigial and have no useful function even though they are still present, like hipbones in whales and boa constrictors, or a tail and cecum (appendix) in humans.Vestigial structures such as pelvic bones in the baleen whale are evidence of evolution.
30 Why Grow a Tail; or Legs… The human embryo has a tail at 4 weeks; which disappears at about 8 weeks.Skinks are a type of lizard. In some species, legs have become so small they no longer function in walking.One explanation:The gene code is present to make the organ, but the function has been lost through change over time. If the organ is not vital to survival, then natural selection would not cause its elimination.
31 Similarities in Embryology Embryos of many animals with back-bones are very similar.
32 It is clear that the same groups of undifferentiated cells develop in the same order to produce the same tissues and organs of all vertebrates, suggesting that they all evolved from a common ancestor.
33 Similarities in DNASimilarities in DNA and protein sequences suggest relatedness.
34 Similarities in Karyotypes Similar karyotypes suggest an evolutionary relationship.Human- 46 chromosomes Chimpanzee- 48 chromosomes
35 Visual Evolution Peppered Moth There is a natural variation in populations of peppered moths.Typica form – lighterCarbonaria form - darker
36 Peppered MothThe light colored form was the predominant form in England prior to the Industrial Revolution.Around the middle of the 19th century the darker form began to appear. It was first reported in By % of the moths in Manchester were the dark variety.In recent years, the burning of cleaner fuels and Clean Air regulations has reduced the pollution there and the lighter colored moths have increased in numbers.https://www.youtube.com/watch?v=aTftyFboC_M