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Early Biological and Geological Thought BI 102 Lecture 13: • Before the scientific method, understanding of the world was based Natural Selection largely on observation • Observation was limited • People rarely traveled more than 20 miles from where they were born • Limited interaction with people, ideas, landscapes, or species outside that radius • Sometimes misunderstood the observations • Example: alchemy
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Early Biological and Geological Thought Early Biological and Geological Thought
• Prevailing thought was that the Earth and life on it are static • Many had attempted to classify living things • The Earth has always existed in its present form • Perhaps the most famous early • All species were created simultaneously in their present form attempt was Aristotle’s • Neither change over time Ladder of Nature • Organisms exist in a linear hierarchy of complexity • Do not change
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Early Biological and Geological Thought Early Biological and Geological Thought
• The age of European exploration (~1450-1800) changed everything • The European discovery of the western hemisphere revealed the • The world was established as spherical, not flat staggering biological and geological diversity on the planet • Explorers drew pictures, collected specimens • Transportation by sea made travel to distant lands faster, safer • Brought knowledge back, spread to other areas of the world • Allowed for the exchange of goods and ideas at an unprecedented • Everyone started asking questions about the nature of the Earth and life on it rate • Many new ideas were proposed
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Early Biological and Geological Thought Early Biological and Geological Thought
• Georges Cuvier (late 1700s – early 1800s) • Charles Lyell (early to mid 1800s) • Considered the father of modern paleontology • Proposed uniformitarianism • Observed that fossils were different in different rock layers • The Earth is much older • Proposed the idea of catastrophism • Shaped by slow, gradual forces • The Earth is relatively young (~10,000 years old) • Same forces are still at work today • Largely shaped by catastrophic events • Limited his work largely to geological thought, but became a major influencer • Catastrophic events cause mass extinction in contemporary biological thought • Species are replaced by new ones
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Early Biological and Geological Thought Early Biological and Geological Thought
• Jean Baptiste Lamarack (late 1700s – early 1800s) • Thomas Malthus (late 1700s – early 1800s) • Believed that species do change over time • Economist and scholar • First to propose a cohesive theory of biological evolution • First to use the term “survival of the fittest” • All species possess an innate drive for perfection • Observed that prosperity leads to population growth • Alchemical processes drive organisms up a ladder of complexity • Population growth leads to wealth disparity and the • Environmental forces adapt species through use and disuse suffering of the poor • Inheritance of acquired characteristics • The poor then die, reducing the population and increasing the prosperity of those who remain • Increased prosperity leads to population growth • “Malthusian Trap”
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Modern Biological and Geological Thought Charles Darwin
• Modern thought regarding changes in living things over time are • Charles Darwin – a smart man, but a bad student based on works from the mid 1800s by two naturalists • Attended a year of medical school and was interested in anatomy, but • Alfred Wallace neglected his studies to learn taxidermy • Charles Darwin • Was sent to a different college to become a cleric, but neglected his studies in favor of riding, shooting, and beetle collecting • Graduated 10th in his class in “ordinary studies”
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Charles Darwin
• Recommended by his former mentor to accompany Robert FitzRoy aboard the HMS Beagle • Expedition to chart the coastline of South America • Self-funded naturalist position • A real disappointment to his father
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Voyage of the HMS Beagle – 1831-1836 Charles Darwin
• Packing list • Spent nearly 5 years sketching, collecting specimens, and theorizing 12 shirts 1 carpet bag • 1 pair slippers Sent specimens, journals, and letters at intervals back to Cambridge 1 pair of light walking shoes 1 microscope (a single lens model by Bancks & Son, London) • Returned a scientific celebrity 1 geological compass 1 plain compass 2 pistols (with spare parts) • Continued his work for the next 20 years, meeting with Lyell and 1 rifle (with spare parts) 1 telescope others to develop his theories on evolution 1 pencil case 1 geological hammer 5 simisometers 3 mountain barometers 1 clinometer 1 camera obscura 1 hygrometer (belonged to FitzRoy) 1 taxidermy book 2-3 Spanish language books 14 other books, including Humboldt's "Personal Narrative" and Lyell’s "Principles of Geology Vol. 1" 1 coin purse (Fanny Owen's gift) 1 pin with a lock of Sarah Owen's hair (Fanny's sister)
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Elements of Darwin’s Theory of Evolution Elements of Darwin’s Theory of Evolution
• Darwin’s theory has 2 main postulates • Postulate 1: Descent with modification 1) Descent with modification • Variation exists within a population 2) Adaptation by natural selection • At least some of these variations are heritable
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Elements of Darwin’s Theory of Evolution Elements of Darwin’s Theory of Evolution
• Postulate 2: Adaptation by natural selection • Postulate 2: Adaptation by natural selection • Not all individuals in a population will survive and reproduce • Not all individuals in a population will survive and reproduce • High reproductive effort • Survival and reproduction are not random • Limited resources • Those with favorable traits leave more offspring • Unequal reproductive success • “Survival of the fittest” • Favorable traits accumulate within a population • Population is modified over time • Evolution
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Natural Selection
• Adaptation by natural selection has nothing to do with effort • It does not give an organism what it “needs” • An advantage must be heritable in order for it to be passed on to offspring • Ultimately the result of mutations in the gametes that provide an advantage
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Natural Selection Natural Selection
• Natural selection is not random • Question • Traits are produced by chance mutations, but only • There is great natural variation in the skin color of frogs persist if they provide an advantage in the • None of the frogs below is poisonous organism’s environment • Which one will be more likely to survive and reproduce?
(Note: Random events do occur that change the patterns of inheritance, but that is not natural selection. We will discuss this later.)
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Natural Selection Evidence for Natural Selection
• What is the evidence for natural selection? • Fossil record • Fossil record • Fossils in older strata don’t look much like species from today • Comparative anatomy • Fossils in newer strata do • DNA homology • Provides a timeline for how species have changed • Pseudogenes
• Artificial selection Youngest • Observations rocks
• Experimental evidence Oldest rocks • Convergent evolution
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Evidence for Natural Selection Evidence for Natural Selection
• Fossil record • Fossil record • Example: evolution of the horse • Transitional fossils • Fossils that show links between different groups of modern species
Pleistocene browsers grazers Pliocene mixed feeders 5MYA • Reptiles to birds Equus 10MYA Archaeopteryx – 145 mya
Astrohippus Caudipteryx – 125 mya Nannippus Onohippidion
Miocene Neohipparion 15MYA Dinohippus Hipparion Calippus Cormohipparion Pliohippus Pseudhipparion Megahippus Protohippus 20MYA Hypohippus Anchitherium Desmatippus Merychippus
25MYA Archaeohippus Parahippus
Oligocene Kalobatippus 30MYA Miohippus 35MYA
40MYA Mesohippus
Eocene 45MYA Epihippus 50MYA Orohippus 55MYA Hyracotherium 60MYA
Hyracotherium Mesohippus Anchitherium Merychippus Neohipparion Nannippus Equus (browsers) (browsers) (browsers) (mixed feeders) (grazers) (grazers) (grazers) 55 mya 40 mya 20 mya 17 mya 14 mya 12 mya 5 mya 27 28
Evidence for Natural Selection Evidence for Natural Selection
• Fossil record • Fossil record Modern toothed whales • Transitional fossils • Transitional fossils • Fossils that show links between different groups of modern species • Fossils that show links between different • Water to land groups of modern species • Land back to the water Rodhocetus swam with an up-and-down motion. Tiktaalik – 375 mya 47 mya
Lobed-finned fish - modern Ambulocetus probably walked on land. 49 mya
Pakicetus attocki lived on land. 55 mya
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Evidence for Natural Selection Evidence for Natural Selection
• Comparative anatomy • Comparative anatomy • Modern species share considerable anatomy with each other, and with • Modern species share considerable anatomy with each other, and with ancient species ancient species • Example: vertebrate forelimbs • Example: vestigial structures
humerus ulna radius Pterodactyl Dolphin carpals Dog metacarpals phalanges Human
Bird
Bat Seal Sheep Shrew FLYING SWIMMING RUNNING GRASPING 31 32
Evidence for Natural Selection Evidence for Natural Selection
• Comparative anatomy • DNA homology • Modern species share considerable anatomy with each other, and with • Modern species have a considerable amount of DNA in common ancient species • How much DNA do you think humans share with these species? • Example: embryonic development • Let’s just look at one gene
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Evidence for Natural Selection
• Pseudogenes • Genes that are still present in a species, but no longer functional 0 • Example: vitamin C synthesis 1 10 11 13 17 28
Evolutionary relationships based on DNA and protein sequence - Cytochrome C amino acid differences
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Evidence for Natural Selection Evidence for Natural Selection
• Pseudogenes • Artificial selection • Genes that are still present in a species, but no longer functional • Humans have been selecting for desirable traits in plants, animals, yeast, and • Example: olfactory genes in mammals bacteria for millenia • Organisms with favorable traits were bred to others with favorable traits • Has led to astounding variety within species in a relatively short period of time Total # of olf. genes % dead
Dog 1,100 18% Mouse 1,500 20% Rat 1,500 19.5% Human 900 63%
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Evidence for Natural Selection Evidence for Natural Selection
• Artificial selection • Artificial selection • Example: Brassica family of vegetables • Example: Teosinte grass vs. modern corn Maize
Teosinte
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Evidence for Natural Selection Evidence for Natural Selection
• Artificial selection • Observations • Example: Domestic dogs • Example: Peppered moth
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Evidence for Natural Selection Evidence for Natural Selection
• Observations • Observations • Example: Antibiotic resistance • Example: Sickle cell anemia
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Evidence for Natural Selection Evidence for Natural Selection
• Experimental evidence • Experimental evidence • Example: Brown anole • Example: Brown anole • Native to Iron Cay, a forested island in the Bahamas • Forests favor long hind limbs • Released in small numbers onto 7 bush-covered islands in 2005 after a • Brush favors shorter hind limbs hurricane wiped out the native lizard population • All anoles had similar hind limb length at the beginning of the • Also released onto 12 forested islands nearby experiment • What would happen over time?
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Evidence for Natural Selection Evidence for Natural Selection
• Experimental evidence • Convergent evolution • Example: Brown anole • Natural selection allows for the persistence of traits that provide an • Lizards on brush-covered islands had shorter hind limbs after several advantage in a particular environment generations • If similar environments exist in different places, we would expect similar traits • Lizards on forested islands still had long hind limbs to develop in the species there • Similar selection pressures produce similar results
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Evidence for Natural Selection Evidence for Natural Selection
• Convergent evolution • Convergent evolution • Example: Placental mammals vs. marsupials • Example: Primates in Madagascar vs continental Africa
Nocturnal Stalking Chasing Niche Burrower Anteater Climber Glider Insectivore Predator Predator
Placental Mole Grasshopper Flying squirrel Mammals mouse Wolf
Lesser anteater Ring-tailed lemur Ocelot
Australian Numbat Marsupials Thylacine Spotted cuscus
Marsupial mole Marsupial Flying phalanger Tasmanian mouse quoll
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Evidence for Natural Selection
• Convergent evolution • Example: Echolocation in the bottlenose dolphin and bats • Similar mutations in the Prestin gene, which is required for hearing in mammals • Both share the ability, even though their common ancestors did not
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