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Transcript
THEORY OF EVOLUTION Footprints activity 14.1 How Did Evolutionary Thought Develop? Evolution is the change over time in the characteristics of a population Population is all the individuals of one species in a particular area Modern biology is based on our understanding that life has evolved, a principle unrealized by early scientists 14.1 How Did Evolutionary Thought Develop? Early biological thought did not include the concept of evolution Pre-Darwinian science was heavily influenced by theological ideas, maintaining that all organisms were created simultaneously by God, and that each distinct life-form was permanently fixed and did not change over time Plato (427–347 B.C.) proposed that each object on Earth was merely a temporary reflection of its divinely inspired “ideal form” 14.1 How Did Evolutionary Thought Develop? Early biological thought did not include the concept of evolution (continued) Pre-Darwinian science was heavily influenced by theological ideas, maintaining that all organisms were created simultaneously by God, and that each distinct life-form was permanently fixed and did not change over time (continued) Aristotle (384–322 B.C.) arranged all organisms on a linear scale of increasing complexity (the “ladder of Nature”) Figure 14-1 Aristotle’s Ladder of Nature Humans Mammals Birds Reptiles and amphibians Whales and porpoises Fish Squids and octopuses Lobsters, crabs, etc. Snails, clams, etc. Insects, spiders, etc. Jellyfishes, sponges, etc. Higher plants Lower plants Inanimate matter 14.1 How Did Evolutionary Thought Develop? Exploration of new lands revealed a staggering diversity of life Europeans were often accompanied by naturalists who observed and collected plants and animals of previously unknown lands By the 1700s observations and collections accumulated by naturalists revealed the true scope of life’s variety The number of species was far greater than expected 14.1 How Did Evolutionary Thought Develop? Exploration of new lands revealed a staggering diversity of life (continued) Revelation of the discoveries led 18th-century naturalists to take note of fascinating patterns Geographic areas possessed their own sets of species Some species closely resembled one another yet differed in some characteristics To some naturalists, these patterns seemed inconsistent with the idea that species were fixed and unchanging Figure 14-2 A timeline of the roots of evolutionary thought Buffon (species created, than evolve) Hutton (gradual geologic change) Lamarck (mechanism of species change) Cuvier (successive catastrophes) Smith (sequence of fossils) Lyell (very old Earth) Darwin (evolution, natural selection) Wallace (evolution, natural selection) 1700 1750 1800 1850 1900 Time line Work on time line activity 14.1 How Did Evolutionary Thought Develop? A few scientists speculated that life had evolved George Louis LeClerc (Comte de Buffon; 1707–1788) Suggested that the original creation provided a relatively small number of founding species Species changed over time through natural processes 14.1 How Did Evolutionary Thought Develop? Fossil discoveries showed that life has changed over time Fossils are the preserved remains or traces of organisms that had died long ago Fossils were the petrified remains of bones, wood, shells, or their impressions left in mud Other fossils included preserved traces such as tracks, burrows, pollen, eggs, and feces Figure 14-3 Types of fossils eggs in nest fossilized feces (coprolites) bones footprint skin impression 14.1 How Did Evolutionary Thought Develop? Fossil discoveries showed that life has changed over time (continued) Significance of fossil distribution The British surveyor William Smith (1769–1839), who studied rock layers and the fossils embedded in them, recognized that certain fossils were always found in the same layers of rock 14.1 How Did Evolutionary Thought Develop? Fossil discoveries showed that life has changed over time (continued) Significance of fossil distribution (continued) The organization of fossils and rock layers was consistent with fossils across different areas Fossil type A always found in a rock layer resting beneath a younger layer containing fossil type B, which is found rested beneath an even younger layer containing fossil type C, and so on 14.1 How Did Evolutionary Thought Develop? Fossil discoveries showed that life has changed over time (continued) Scientists of the period discovered that fossil remains showed remarkable progression Most fossils found in the oldest layers were very different from modern organisms The resemblance to modern organisms gradually increased in progressively younger rocks Many of the fossilized species were extinct, which means no members of the species still lived on Earth 14.1 How Did Evolutionary Thought Develop? Fossil discoveries showed that life has changed over time (continued) Scientists concluded that Different types of organisms had lived at different times in the past This countered the view that species were created at one time and did not change afterward Figure 14-4 Different fossils are found in different rock layers youngest rocks oldest rocks Trilobite Seed ferns Allosaurus 14.1 How Did Evolutionary Thought Develop? Some scientists devised non-evolutionary explanations for fossils To account for the existence of extinct species while preserving the notion of a single creation by God, Georges Cuvier (1769– 1832) proposed the theory of catastrophism The Great Flood described in the Bible produced layers of rock and destroyed many species, fossilizing some of their remains in the process The organisms of the modern-day species are the survivors of these catastrophes 14.1 How Did Evolutionary Thought Develop? Geology provided evidence that the Earth is exceedingly old Charles Lyell (1797–1875) challenged Cuvier’s hypothesis of a world shaped by successive catastrophes Lyell, building on the earlier thinking of Hutton, considered the forces involved in catastrophes and concluded no need to invoke catastrophes to explain the finding of geology 14.1 How Did Evolutionary Thought Develop? Geology provided evidence that the Earth is exceedingly old (continued) Lyell presented the idea of uniformitarianism to explain that Earth’s landscape was produced by past action of the same geological processes observed today The acceptance of uniformitarianism by scientists implied that Earth is ancient 14.1 How Did Evolutionary Thought Develop? Darwin and Wallace proposed a mechanism of evolution Darwin and Wallace independently proposed that organisms evolved by natural selection Both presented papers to the Linnaean Society in London in 1858 Darwin published On the Origin of Species by Means of Natural Selection in 1859 How Do We Know How Old a Fossil Is? 17-1 http://education-portal.com/academy/lesson/the-history-of-life-on-earth-timeline-and-characteristicsof-major-eras.html#lesson (cuts off after a while) 1. 2. Relative Dating (before 20th century) a. Law of Superposition - Fossils in deeper rock layers were older than fossils found in shallower rock layers Absolute Dating (1896) a. Radiometric dating – when the nuclei of radioactive elements spontaneously break down, or decay, into other elements b. Each radioactive element decays at a different rates How Do We Know How Old a Fossil Is? 17-1 2. Radiometric dating (cont.) a. Time it takes for half of a radioactive element’s (isotope) nuclei to decay at a specific rate is called half-life. b. Half-life of Carbon-14 = 5,730 years Half-life of Potassium-40 = 1.25 billion years c. Can estimate how much time has passed by measuring the proportion of decayed nuclei to undecayed nulcei Half-lives 256 14C atoms at time 0 128 14C and 128 14N atoms after 5,730 years or 1 half-life 64 14C and 192 14N atoms after 11,460 years or 2 half-lives 32 14C and 224 14N atoms after 17,190 years or 3 half-lives Half-lives 16 14C and 240 14N atoms after 22,920 years or 4 half-lives 8 14C and 248 14N atoms after 28,650 years or 5 half-lives Half-lives 4 14C and 252 14N atoms after 34,380 years or 6 half-lives 2 14C and 254 14N atoms after 40,110 years or 7 half-lives Half-lives Proportion of Isotope Left vs. Half Lives Proportion of isotope left 1 1/2 1/4 1/8 1/16 0 1 2 3 Half-lives 4 5 How Do We Know How Old a Fossil Is? 17-1 3. 4. Hyphen notation of radioisotopes (element symbol and mass number) Examples: C-12, C-14, O-16, O-18 Carbon-14 dating – compare ratio of C-14 and C12 and use the ratio to determine age ISOTOPE Carbon-14 Uranium-235 Potassium-40 Uranium-238 HALF LIFE (years) 5,730 704,000,000 1,250,000,000 4,500,000,000 How Do We Know How Old a Fossil Is? 17-1 Sample Problem 1: The half-life of Thorium-230 is 75,000 years. If a scientist has 40.0g of Thorium, how much will remain after 225,000 years? ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ How many half-lives have past? 225-75 = 150 150-75 = 75 75-75 = 0 3 half-lives have past How much Thorium is left? 40/2 = 20g 20/2 = 10g 10/2 = 5g 5g of Thorium remaining after 225,000 years 2. The half life of carbon-14 is 5,730 years. How long will it take for ½ of the sample to decay? 1 half-life = 5,370years = ½ the sample decays If a biologist has 64.0g of C-14, how long will it take until 8.0g remain un-decayed? 64/2 = 32g 1 half-life 5,730 x 3 half-lives = 32/2 = 16g 1 half-life 17, 190 years 16/2 = 8g 1 half-life 3 half-lives 3. Labs Half life lab Fossil hunt 14.2 How Does Natural Selection Work? Darwin and Wallace proposed that life’s diverse forms arose through the process of descent with modification Individuals in each generation differ slightly from the members of the preceding generation Over long time periods, small differences accumulate to produce major transformations A. LAMARCK 1. Inheritance of acquired traitscharacteristics developed during an organisms' lifetime would be passed on to offspring. a. proved untrue because traits are determined by genes. b. Law of use and disuse- the more an organism uses some part, the more developed it will became, the less used , the weaker it becomes. B.WEISMANN 1. Disproved Lamarck A. cut off tails of mice and mated them for 20 generations i. all offspring had tails C. Charles Darwin 1. 2. 3. Theory of Natural Selection Overproduction- more offspring produced than can survive. Competition- due to limited resources Variation- differences between individuals 4. 5. 6. Adaptation- characteristics that helps an organism to survive better in one environment. Natural selection- organisms with beneficial adaptations survive and reproduce Speciation- over a very long period of time new species form due to the accumulation of adaption (finches) Darwin Darwin He was born in England in 1809. Invalid mother died when he was 8 years old. He had poor grades in school. Father was a doctor and wanted him to become a doctor. He went to medical school, then tried to become a clergyman. Neither worked. Darwin Met a botanist named Prof. Henslow 1831 set sail on the Beagle as a naturalist. Was seasick most of the time. He started making collections of skins and fossils Discovered band of seashells high up in the mountains He began noticing differences in beaks of finches on different islands. 3. Adaptive radiation- divergent evolution One species occupies new environments and creates a new species in each Darwin’s finches Darwin 1836 Beagle returns – Darwin had collected 1500 animals, 4000 species. Through transmutation –( name for evolution he began studying horse and pigeon breeding. 1839 – Voyage of the Beagle was published 1842- wrote his theory of Evolution Darwin 1859- Origin of Species was first published It was not well accepted. 1871- The Descent of Man was published The Beagle Only 90 foot long, but carrying 74 people. Travels of the Beagle 1. Types of Adaptations adaptation- trait that improves chances of survival in a specific environment. A. Structural structural – involve body of the organism A. webbed feet, wings I. Evidence of Evolution B. Comparative Anatomy 1. homologous structures a. similar structure, evolution, development b. wing, arm, flipper) 2. analogous structures a. similar function b. wing of a bird and an insect Homologous vs Analogous Structures I. Evidence of Evolution B. Comparative Anatomy 3. vestigial structures a. useful in past organisms but not now b. appendix, tail vertebrae, ear muscles Vestigial Structures Appendix in Humans Leg Bones in a Whale Work on proof of evolution lab I. Evidence of Evolution C. Embryology Similarities 1. Haeckel(1834-1919) [German] a. “ontogeny recapitulate phylogeny” 1) embryo undergoes changes that repeat evolutionary development Diagram Showing Similarities in Early Stages of Embryo Development I. Evidence of Evolution D. Biochemistry 1. similarity in amino acids in specific proteins 2. similarity in RNA and DNA base sequences I. Evidence of Evolution D. Biochemistry 1. similarity in amino acids in specific proteins 2. similarity in RNA and DNA base sequences Comparing Amino Acid Differences of Several Organisms to Humans Work together in groups of two on amino acid sequence lab. II.Rates of Evolution A. Gradualism- evolution occurs slowly and continuously over time according to Darwin. B. Punctuated equilibrium- species stay the same for a long period of time then there is a rapid-Gould and Eldrege 1. fossil record seems to support this, but no evidence for how such change could occur so quickly can be found. III. Patterns of Evolution A. Coevolution 1. changes in two or more species closely associated 2. examples a. predator and prey b. parasite and host c. plants and plant pollinators III. Patterns of Evolution B. Convergent Evolution 1. similar phenotypes are selected (b/c of environment) but ancestors are very different a. natural selection of analogous structures because of envir. demands. 2. examples a. wings in insects and birds b. fins & shape of sharks, fish, porpoise Examples of Convergent Evolution III. Patterns of Evolution C. Divergent Evolution 1. two or more related populations or species become more dissimilar a. speciation - new species may form 2. example geographic isolation a. brown bear polar bear III. Patterns of Evolution C. Divergent Evolution 3. adaptive radiation a. many species evolve from same ancestor 1) ancestor migrates to different environments (example) Galapagos finches Adaptive Radiation – Darwin’s Finches Beak shape Depends Upon Food Source Adaptive Radiation – Hawaiian Honeycreepers Frogs and the Venomous Path- read and answer questions. C. Protection Camouflage- blends into environment Warning coloration- bright color warns of its danger ( monarch ) Mimicry- copying a successful strategy of another ( viceroy) Camouflage lab Speciation Formation of a species results from isolation and adaptive radiation. 1. geographic isolation-population divided by mountain, desert, river etc. 2. reproductive isolation – two groups cannot interbreed successfully. Different courtship behavior, mating times, mating calls Incompatible sex organs In the struggle for existence, individuals with a suite of traits that makes them better adapted to the environment seem to leave more offspring than poorly adapted individuals. This is the essence of “natural selection”. Over time, rabbits in general tend to run faster that their ancestors… There is a lot of variation in a typical population Eduardo Kac # Low Medium High In a given population of rabbits, some run faster than others and escape predators. Their offspring run fast too… Speciation The evolution of new species. IV. Variation in Populations A. Distribution of variations 1. graph is a bell curve B. Natural Selection and Changes in Populations 1. Stabilizing Selection – favors average form 2. Directional Selection – average shifts to one extreme or the other 3. Disruptive Selection – extreme forms are favored- number of individuals with the average form is reduced Stabilizing Selection Directional Selection Disruptive Selection Comparing Types of Selection Comparing Three Types of Selection Types selection: Normal- bell curve Stabilizing selection- average chosen Directional – extreme chosen Disruptive – both extreme chosen leads to speciation B. Physiological Physiological- involve metabolism Ex: venom, insecticide X X X X The few survivors from the early applications of the insecticide are those insects with genes that enable them to resist the chemical attack. Only these resistant individuals reproduce, passing on their resistance to their offspring. In each generation the percentage of insecticide-resistant individuals increases. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Other Modern-day Examples of Natural Selection and Evolutionary Change Antibiotic Resistance (NEVER quit taking a prescription of antibiotics before the bottle is empty) AZT resistance (now chemical cocktails are required) Peppered Moth and Air Pollution (moths become speckled to blend into soot -covered trees)