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Ch.14 – History of Life 14.1 – Fossil Evidence of Change Fossils have been found of organisms that no longer live on Earth. Traces (fossils) of modern organisms can only be dated back to a certain point in the Earth’s 4.6 billion year history. Therefore, Life on Earth has changed (EVOLVED) over the course of the Earth’s history and continue to do so. What do we know about fossils and their age? How/Why do living things change over time? Ch.14 – History of Life Fossils Trace 14.1 – Fossil Evidence of Change Any evidence of an organism Replacement Petrified Preserved Mold & Cast Ch.14 – History of Life 14.1 – Fossil Evidence of Change Nearly all fossils form in sedimentary rock because it prevents rapid decomposition (99% of all living things left no fossils behind) Ch.14 – History of Life 14.1 – Fossil Evidence of Change Fossil Dating Relative Dating Absolute Dating Based on the law of superposition: newer layers of rock form on top of older layers Radiometric Dating -Cannot give exact age -Earth’s geology is constantly shifting changing the position of artifacts Uses the half life of radioactive isotopes in order to determine specific age. Ch.14 – History of Life 14.1 – Fossil Evidence of Change Fossil Dating Relative Dating Absolute Dating Based on the law of superposition: newer layers of rock form on top of older layers Radiometric Dating -Cannot give exact age -Earth’s geology is constantly shifting changing the position of artifacts Uses the half life of radioactive isotopes in order to determine specific age. Ch.14 – History of Life 14.1 – Fossil Evidence of Change Absolute Dating U238 decays to Pb206 Half-life – 4.5 billion years C14 decays to N14 Half-life – 5730 years Ch.14 – History of Life 14.1 – Fossil Evidence of Change Geologic Time Scale Precambrian 4600mya – 542mya •Earth formed about 4.6 billion years ago •It took about 500 million years for the crust to form and for water to start collecting on the surface •Prokaryotic & eukaryotic unicellular organisms emerge •Autotrophic prokaryotes begin to enrich the atmosphere with O2. •Multicellular organisms emerge (1st animals) Ch.14 – History of Life Paleozoic 14.1 – Fossil Evidence of Change 488mya – 251mya •Animals diversify •1st plants •1st vertebrates •Life moves out of the oceans •Insects, amphibians, reptiles scatter •Ferns & Evergreens cover the Earth Ch.14 – History of Life Mesozoic 14.1 – Fossil Evidence of Change 199mya – 65mya •1st mammals •Dinosaurs •Birds •Gymnosperms (seed-bearing plants) diversify •Flowering plants appear •Mass extinction wiped out all dinosaurs, except for the birds, at the end of the era. Ch.14 – History of Life Cenozoic 14.1 – Fossil Evidence of Change 55mya – present •Mammals diversify and scatter •Flowering plants scatter •Primates appear •Humans create civilizations and pollution Ch.14 – History of Life 14.2 – Origin of Life Origin of Life Early Ideas Spontaneous Generation Life arises from non-life Francisco Reddi 1668 Louis Pasteur mid 1800’s Biogenesis Life arises from existing life Ch.14 – History of Life 14.2 – Origin of Life Origin of Life Origin Movie Ch.15 – Evolution 15.1 – Darwin’s Theory of Natural Selection A new era of biology began on November 24, 1859, the day Charles Darwin published On the Origin of Species by Means of Natural Selection Darwin made two main points in his book: 1. Many current species are descendants of ancestral species 2. Natural selection is the mechanism for this evolutionary process Ch.15 – Evolution 15.1 – Darwin’s Theory of Natural Selection Darwin’s Influences: Geologists Hutton and Lyell (late 1700’s) perceived that changes in Earth’s surface can result from slow continuous actions still operating today (gradualism) Thomas Robert Malthus (late 1700’s) hypothesized that in nature plants and animals produce far more offspring than can survive, and that Man too is capable of overproducing if left unchecked Ch.15 – Evolution 15.1 – Darwin’s Theory of Natural Selection Darwin’s Observations: After graduating college Darwin was accepted on board the HMS Beagle, which circled the world from 1831-1836 He observed plant and animal adaptations from many diverse environments Ch.15 – Evolution 15.1 – Darwin’s Theory of Natural Selection Darwin’s most famous observations were of finches found on the Galapagos Islands off the coast of Ecuador Many of the islands had unique climate & vegetation Similar looking finches found on the different islands had different adaptations from each other and were different from finches found on the mainland Ch.15 – Evolution 15.1 – Darwin’s Theory of Natural Selection Upon return to England Darwin began reflecting on his observations and started hypothesizing about how populations change over time. He did not agree with French scientist Jean-Baptiste Lamarck that living things changed due to use and disuse of certain characteristics Ch.15 – Evolution 15.1 – Darwin’s Theory of Natural Selection With his knowledge of artificial selection – done by farmers for centuries in order to improve their livestock or crop populations, and the observations made on the HMS Beagle, Darwin put together his theory of Natural Selection Heritable Genetic Variation + Overproduction = Reproductive Advantage Original Population New Population Descent with Modification Ch.15 – Evolution 15.1 – Darwin’s Theory of Natural Selection Survival of the Fittest An adaptation is any characteristic that increases fitness, which is defined as the ability to survive and to produce fertile offspring Living things adapt to their environment Genetic Variation + Overproduction = Reproductive Advantage Original Population New Population Descent with Modification Ch.15 – Evolution Evidence for Evolution The Fossil Record Comparative Anatomy Comparative Embryology Comparative Biochemistry 15.2 - Evidence for Evolution The Darwinian view of life predicts that evolutionary transitions should leave signs in the fossil record Paleontologists have discovered fossils of many such transitional forms Ch.15 – Evolution The Fossil Record 15.2 - Evidence for Evolution The Darwinian view of life predicts that evolutionary transitions should leave signs in the fossil record Paleontologists have discovered fossils of many such transitional forms Ch.15 – Evolution Comparative Anatomy 15.2 - Evidence for Evolution Most animals show similarities in internal structure Homologous Structures Vestigial Structures Similar structure – different use Structures with reduced function (“leftover parts”) Ch.15 – Evolution 15.2 - Evidence for Evolution Comparative Embryology Vertebrate embryos exhibit homologous structures during certain phases of development Ch.15 – Evolution 15.2 - Evidence for Evolution Insert info about biological resistance…visualizing evolution… Ch.15 – Evolution Comparative Biochemistry 15.2 - Evidence for Evolution Many organisms share complex biomolecules. The more closely related the more similar the molecules 1. How does the concept of “descent with modification” explain both the unity and diversity of life? 2. Explain how overreproduction and heritable variation relate to evolution by natural selection 3. If you found a fossil of a mammal that lived high in the Andes, would you predict that it would more closely resemble present –day mammals from South American jungles or present –day mammals that live high in Asian mountains? Explain. Have you been paying attention? 4. Increased UV irradiation causes the skin of humans to become more darkly pigmented over a period of days. The notion that the offspring of such tanned individuals should consequently inherit darkened skin from their parents is consistent with the ideas of whom? 5. Most species of whale have 5 phalange (finger bones) supporting their flippers. Why would a whale have fingers? What would you call those phalange? Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory Macroevolution Population Genetics Natural selection works on individuals but only populations evolve Evolution is the change of the allelic frequency in a population Bb bb BB BB bb BB Bb bb Bb bb bb BB bb BB Bb Bb bb BB 20 bugs 40 alleles for color (incompletely dominant) Bb bb bb BB bb bb Bb bb Bb bb bb bb Bb bb Bb Bb Bb bb B – 12/40 = .30 Bb b - 28/40 = .70 bb BB Bb B – 18/40 = .45 b - 22/40 = .55 Over Time Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory Populations evolve due to three main causes: Natural Selection – Genetic Drift – Gene Flow Natural Selection alters populations in one of three ways Original Population Distribution Disruptive Selection Stabilizing Selection Directional Selection The average is selected for Both extremes are selected for One Extreme is selected for Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory Populations evolve due tochanges three main Genetic Drift is random in a causes: gene pool Natural Selection – Genetic Drift – Gene Flow usually due to independent assortment Usually only occurs in small populations 2 Examples Founder Effect Bottleneck Effect A small sample of the population relocates XX XX XXX XXX XXX X X X X X Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory Populations evolve due to three main causes: Gene Flow is the exchange of genes between Natural Selection – Genetic Drift – Gene Flow populations from migration Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory Populations can also evolve due to nonrandom mating and mutations Therefore, according to the Hardy-Weinberg Principle A population in genetic equilibrium must meet 5 conditions: No Genetic Drift No Gene Flow No Mutation Random Mating No Natural Selection Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory Speciation New species arise because of reproductive isolation Reproductive isolation either occurs with a physical barrier or without a physical barrier Sympatric Allopatric Speciation Animation Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory There are two hypothesis as to how different species come to exist Gradualism Punctuated Equilibrium Changes occur little by little Changes occur rapidly between periods of little change Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory Patterns of Evolution Divergent Evolution Convergent Evolution or Adaptive Radiation Organisms not closely related evolve similar traits Many species arise from one original species Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory Patterns of Evolution Coevolution Many species evolve in close relationship with other species