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Transcript
Chapter 16.1: Darwin’s Theory of Evolution: Objectives: 1. State Charles Darwin’s contribution to science. 2. Describe the three patterns of biodiversity noted by Darwin. Darwin’s Epic Journey Charles Darwin – Naturalist Born in England in 1809 Developed the theory of evolution. Darwin’s Epic Journey Dates: February 12th, 1831 Ship: H.M.S. Beagle Destination: Voyage around the world Findings: Collected thousands of plant & animal specimens to propose a hypothesis about how life changes over time. Differences Among Organisms • • Species: A group of organisms that can mate with one another to produce fertile offspring. Adaptation: Characteristic that helps an organism survive and reproduce in its environment. Observations Aboard the Beagle Darwin noticed 3 patterns of biological diversity: Species vary globally Species vary locally Species vary over time Species Vary Globally Similar species in different continents? South America: Rheas Africa: Ostrich Australia: Emu Conclusion: Similar environments produce species with similar adaptations. Species Vary Locally: Galapagos Islands Related species had different adaptations in different parts of the same continent. Example: Hood Island Tortoise & Isabela Island Tortoise Finches Isabela Island Tortoise Hood Island Tortoise Species Vary Locally: Galapagos Islands Variation among finches on different islands Species Vary Over Time Darwin also collected fossils. Fossils: Traces of organisms or “footprints” Fossil Record: Timeline of life, organizing fossils by their estimated ages and physical similarities. Species Vary Over Time Darwin’s observations of fossils: Extinct animals were similar to living species Example: Extinct Glyptodont vs. Armadillo Do Species Change over Time? As populations and their environment change over time, new species form. Evolution: The process in which populations gradually change over time. Chapter 16.2 Essential Questions What did Hutton and Lyell conclude about Earth’s history? How did Lamarck propose that species evolve? What was Malthus’s view of population growth? How is inherited variation used in artificial selection? Ideas That Shaped Darwin’s Thinking Geologists Lyell + Hutton discovered that EARTH: Was much older than previously thought Changed and is still changing in the same pattern Principles of Geology, 1809 These ideas helped shaped Darwin’s theories about how organisms adapt to changes on Earth Lamarck’s Evolutionary Hypotheses Jean Baptiste Lamarck: 1st naturalist to study adaptations Suggested 2 theories: Acquired characteristics Inheritance of acquired characteristics Lamarck’s Evolutionary Hypotheses Theory of acquired characteristics (1809): Organisms acquire traits during their lifetime to adapt to their environment Driven by innate tendency toward perfection Pertained to both use and disuse Theory of inheritance of acquired characteristics: Traits acquired during an organism’s lifetime can be passed on to their offspring. Example: Giraffe’s neck Lamarck Was Wrong!!! Phenotypic changes do not result in genotypic changes. However, he was the first to link organism’s environment to its body changes. Darwin built his theory using Lamark’s ideas. Population Growth Thomas Malthus (1798) The rate of people being born is higher than the rate of people dying Theory: If this rate continues, there won’t be enough food and living space. Darwin related this idea to other organisms, and started wondering why overcrowding does not exist in nature. Artificial Selection Darwin studied artificial selection by plant and animal breeders. Artificial selection: Selective breeding i.e. Can produce variation among species (pigeons) Darwin realized variation in nature was key for evolution to occur. Darwin’s Thinking – Ideas About Population Only a limited number of individuals survive to reproduce in a population. Survivors must have favorable traits. Only the strongest species will go on to have offspring with these favorable traits. Chapter 16.3 Essential Questions Under what conditions does natural selection occur? What does Darwin’s mechanism for evolution suggest about living and extinct species? Natural Selection 1859, Darwin’s theory of evolution was published On the Origin of Species by Means of Natural Selection Theory of Natural Selection: 1. 2. 3. The Struggle for Existence Variation and Adaptation Survival of the Fittest Natural Selection 1. The Struggle for Existence Population rate forces species to compete for resources Natural Selection 2. Variation and Adaptation Variations are due to adaptations to the environment Adaptation: Characteristics increasing ones chance of survival Natural Selection 3. Survival of the Fittest Adaptations High fitness Individuals Low effect an individual’s fitness have a better advantage fitness Individuals die before having offspring Natural Selection Three types of Adaptations: 1. 2. 3. Structural Physiological Behavioral 1. Structural Adaptations Camouflage Mimicry Warning Coloration Structural Adaptations Duck---webbed feet Fish---gills Giraffe---long neck Beaver---large teeth Whale---blubber Snake---flexible jaw Platypus---bill 2. Physiological Adaptations Chemicals Toxins Body Temperature 3. Behavioral Adaptations Scaring Predators Hibernating Migrating in “V” Staying in Groups Mating Calls Darwin’s Theory of Natural Selection Natural Selection: Individuals better adapted to their environment survive and reproduce more successfully than less well adapted individuals Natural Selection – Insect Resistance Darwin’s Theory of Natural Selection Genetics and Evolution Darwin’s theory (1858) lacked explanation of inheritance of traits and variation Mendelian genetics (1900s) Variation is due to differences in genes Darwin Presents His Case Over time adaptation could cause successful species to evolve into new species Living species are descended from common ancestors (Descent with modification) 1st evolutionary tree Principle of common descent All species are related to a common ancestor (tree of life) Evidence of Evolution Exploring Various Lines of Evidence for the Theory of Evolution Lines of Evidence • Biogeography • Comparative Anatomy • Embryology • Fossil Record • DNA Sequences Biogeography • Biogeography is the study of the global pattern of distribution of species and their ancestors. Patterns in Distribution (2 Types) • Closely Related But Different – Finches developed different variations depending on the environment of their island but all had a common ancestor from the mainland. • Distantly Related but Similar – Similar species (rheas, ostrich, emu) in different grasslands (Europe, Australia, Africa) do not share a common ancestor, but developed similar adaptations. Evidence for Evolution – Radioactive dating is a technique used to date materials such as rocks, by comparing its abundance of a naturally occurring radioactive isotope to its known decay rates. – Determined Earth is about 4.5 billion years old Evidence for Evolution: The Fossil Record Evidence for Evolution • Fossil Record – Provides evidence about the order in which species have existed Whale Evolution Comparing Anatomy & Embryology • Homologous Structures: Similarities in structures b/w species suggest they descended from a common ancestor • Includes bone structures and embryological development Comparative Anatomy • Homologous Structures • Note the colorcoded bones for the limbs of these 4 mammals – though different, they share many similar bones. Comparative Anatomy • Same arrangement of bones in cats, dolphins, bats, and humans suggest they share a common ancestor. Comparing Anatomy & Embryology • Analogous Structures: Body parts that share common function, but not structure. Do not share a common ancestor. – Example: Wing of a bird and an insect • Vestigial structures: Structures inherited from ancestors that are no longer necessary and have lost their function. – Ex: Hip bone of whale Genetics and Molecular Biology • Genetics gives evidence of common descent among organisms. • We also know that variation is due to shuffling and crossing over in meiosis. DNA Sequences • Scientists are able to isolate pieces of DNA. • Species that are more closely related tend to have more similarities in their DNA. DNA Sequences • Leptin = Protein hormone important for regulating body weight and metabolism • Mice without properly functioning leptin gene are morbidly obese (right) compared to normal mice (left). Testing Natural Selection • Darwin’s finches hypothesis: – Beaks of finch species evolved to adapt to the type of food available on the island. – Recently tested by Peter and Rosemary Grant to be true. Testing Natural Selection • Natural Selection: – The Grants found that if the environment changes quickly and unexpectedly, that finch populations could evolve within decades, confirming that competition and environmental change drive natural selection. – They also showed that variation increases a populations chances of survival. Biogeography • Marsupial Marsupialsdistribution are a group across of mammals the globe: that http://evolution.berkeley.edu/evolibrary/arti give birth to live young that develop in an cle/0_0_0/lines_11 outer pouch of the mother. Bandicoot • Distribution today split on two sides of globe – how? • Review a few facts of the distribution and Koala marsupials, as well as the history of the Earth, then formulate hypothesis behind Opossum distribution Sugar Glider Kangaroo Biogeography How do you think some marsupials ended up halfway across the world from the others? Biogeography Continental Drift over millions of years – watch the movement of land masses Biogeography Continental Drift + Distribution of Marsupials