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The Origin and Evolution of Life The History of Life on Earth Chapters 21& 22 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Evolutionary Thought • What is evolution? – Evolution simply mean “change” • The problem comes when trying to determine how life began • Through the years, many people have tried to understand and explain how life could have come about (Aristotle) • Why try to explain? Theory of Evolution • Enter Charles Darwin • Charles Darwin was 23 years old when he was convinced to take the place of the naturalist on the H.M.S. Beagle. • The ship sailed for 5 years (1831-36) circling the globe discovering new species of plants and animals. • Darwin was the person who drew all the illustrations of animals and plants discovered on the voyage. Voyage of the HMS Beagle On the Origin of Species by Means of Natural Selection by Charles Darwin • In 1838, Darwin read Malthus: “populations… tend to increase beyond capacity of their environment to support them” • Studied, experimented, pondered and wrote for 20 years • 1858 Darwin read Wallace’s essay on Natural Selection—pushed Darwin to finish book • Published in 1859 • Huge hit Darwin’s Theories • Darwin eventually came up with five theories: • 1. Perpetual change—basic theory or foundation-- now considered a scientific fact, species change. • 2. Multiplication of species—new species formed by splitting and transforming of older ones. Species will increase through time, although most will become extinct. • • 3. Gradualism—gradual minute changes over a long period of time. • 4. Common descent—phylogeny: everything came from one common ancestor “into which life was first breathed.” • 5. Natural Selection—Variation among organisms Darwin’s “Finches” Early Tree of Life (1874) Ernst Haeckel showing “common descent” Modern Darwinism • Neo-Dawinism: With the advent of genetics, came population genetics • out of that came two fields of study: – 1. Microevolution: evolutionary changes in frequencies of variant forms of genes (alleles) within populations • Peppered moths of England Peppered Moths Modern Darwinism – 2. Macroevolution: evolution on a grand scale – Speciation: new species formed • What determines a Species? • HOW? • Gradual divergence? –proceeds over time more or less steadily • Punctuated equilibrium? – discontinuous change: long periods of time and then a short burst of speciation – Extinctions: • Mass extinctions: where large numbers of taxa become extinct all at once. Darwinian Evolution Pros • Natural Selection (“survival of the fittest”) works • Some organisms do seem to resemble each other • Change happens within a species • DNA is the key component of all living things Darwinian Evolution Cons • Theory does not provide a testable hypothesis • Fossil record problems – Huge gaps exist for “transition” species – Fossil record can be “upside down” • Structure evolution requires significant modifications for proper functioning • -- Longer arms require different muscular-skeletal support -- sensory: eyes, ears, nerves? -- asexual to sexual mechanisms * Some systems cannot evolve through single mutations; they need many parts to function in unison at the same time -- Darwin’s “black box” UNDERSTAND THIS: Darwinian evolution as presented in the book would take HUGE amounts of time. That is why it is essential that evolutionists believe in an OLD EARTH!!! Without billions of years available, the argument for evolution would not be possible. For Darwinian evolution to have happened, two things had to happen: 1. Appearance of living things from lifeless chemicals 2. Multiplication and diversity of all species Neither of these has ever been seen or have ever been reproduced! Fossils • Any evidence of former life – Can include actual or altered remains of plants and animals – Also less direct evidence such as leaf imprints, dinosaur footprints and bat droppings • Knowledge of rocks containing fossils can provide clues about their origins Types of Fossils 1. Preserved whole organisms – Must be protected from scavengers and decomposers • • • • Freezing Entombment Amber Ash 2. Preserved hard parts – More easily preserved – Composed of calcium carbonate, calcium phosphate, silica, chitin • Shells, bones, teeth, exoskeleton, spores Types of Fossils 3. Petrified fossils – Formed by modification of original chemicals – Takes place over long time 4. Fossils that are not remains – Footprints, tunnels, nests, dung Trilobites Dinosaur Eggs Crinoids Fern Frond Ashfalls Fossil Bed Using Fossils to Determine the Order of Geological Events • Principle of succession – Rocks can be placed in chronological position based on fossils • Index fossils – Distinctive and widely distributed plant or animal fossils – Lived only briefly with a common extinction time – Allow age correlations of exposed rock in different locations • Relative dating technique • Used for sedimentary rock –not found in igneous or metamorphic rock Intermediate Fossils? (Celancanth) Taxonomy: The science of naming and grouping organisms • Modern system begun by Carolus Linnaeus • Bi-nominal system of nomencla ture Two name system: – Genus • Group of closely related species – Specific epithet • Identifies species within genus • Placed organisms into groups – Two kingdoms • Plantae and Animalia Modern System • 3 Domains: 1. Archaea Ancient bacteria 2. Eubacteria Kingdom Prokaryotes Bacteria 3. Eucarya Kingdoms Protista – single cell Fungi – multicellular, cell walls, nonphotosynthetic Plantae – multicellular, cell walls, photosynthetic Animalia – multicellular, no cells walls, non-photosynthetic Protista Fungi Plantae Animalia 8 Common Taxanomic Groups • Domain (Eucarya) Kingdom (Animalia) Phylum (Chordata) Class (Vertebrata) Order (Primates) Family (Hominidae) Genus (Homo) species (sapiens)