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Copyright Pearson Prentice Hall Copyright Pearson Prentice Hall Voyage of the Beagle In 1831, Darwin set sail from England aboard the H.M.S. Beagle for a voyage around the world. Copyright Pearson Prentice Hall Darwin's Observations He observed many plants and animals were well suited to the environments they inhabited. He was impressed by which organisms survived and produced offspring. Darwin was confused by species lived and did not live. Copyright Pearson Prentice Hall Before Darwin, there were scientists who shaped the way that scientists viewed a round world. Copyright Pearson Prentice Hall Hutton and Lyell's Principles of Geology 1. Scientists must explain past events in terms of observed processes. 2. Processes that shaped the Earth millions of years ago still continue. Copyright Pearson Prentice Hall Understanding geology influenced Darwin: If the Earth could change over time, life might change too. It would have taken years for life to change like Lyell suggested. This is only possible if the Earth is extremely old. Copyright Pearson Prentice Hall Lamarck's Evolution Hypotheses Jean-Baptiste Lamarck recognized that: living things have changed over time. all species were descended from other species. organisms were adapted to their environments. Copyright Pearson Prentice Hall Lamarck proposed: 1. selective use or disuse of organs: organisms gained or lost certain traits during their lifetime. 2. Traits could then be passed on to their offspring. 3. Over time, this process led to change in a species. Flaws: Tendency toward perfection Use and Disuse Copyright Pearson Prentice Hall Copyright Pearson Prentice Hall Lamarck's Hypothesis A male fiddler crab uses its front claw to ward off predators and to attract mates. Copyright Pearson Prentice Hall Lamarck's Hypothesis Because the front claw is used repeatedly, it becomes larger. This characteristic (large claw) is passed onto its offspring. Copyright Pearson Prentice Hall Evaluating Lamarck's Hypotheses Lamarck did not know: how traits are inherited. that an organism’s behavior has no effect on its heritable characteristics. His idea of evolution was wrong. Copyright Pearson Prentice Hall Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone. Copyright Pearson Prentice Hall Hutton and Lyell recognized that geological processes of the past differ from those of the present. indicate that Earth is many millions of years old. operate quickly, often over thousands of years. always involve violent events like volcanoes, earthquakes, and floods. Copyright Pearson Prentice Hall Which of the following scientists proposed the hypothesis of selective use and disuse? Charles Darwin Jean-Baptiste Lamarck Thomas Malthus Charles Lyell Copyright Pearson Prentice Hall The scientist that proposed that Earth is shaped by geological forces that took place over long periods of time is: Malthus Hutton Darwin Lamarck Copyright Pearson Prentice Hall Copyright Pearson Prentice Hall Natural selection affects which individuals survive and reproduce and which do not. Evolution: any change over time in the relative frequencies of alleles in a population. Populations, not individual organisms, can evolve over time. Natural selection on single-gene traits can lead to changes in allele frequencies and thus to evolution. Copyright Pearson Prentice Hall Copyright Pearson Prentice Hall Natural selection can affect the distributions of phenotypes in any of three ways: directional selection stabilizing selection disruptive selection Copyright Pearson Prentice Hall Directional Selection: when individuals at one end of the curve have higher fitness than individuals in the middle or at the other end. Copyright Pearson Prentice Hall Stabilizing Selection: when individuals near the center of the curve have higher fitness than individuals at either end of the curve. Copyright Pearson Prentice Hall Disruptive Selection: when individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle. Copyright Pearson Prentice Hall Genetic drift (random change in allele frequency) occurs when a small group of individuals colonizes a new habitat. Individuals may carry alleles in different relative frequencies than did the larger population from which they came. Copyright Pearson Prentice Hall Copyright Pearson Prentice Hall Evolution Versus Genetic Equilibrium The Hardy-Weinberg principle states that allele frequencies remain constant unless one or more factors cause the frequencies to change. Genetic equilibrium: When allele frequencies remain constant. Copyright Pearson Prentice Hall Five conditions are required to maintain genetic equilibrium from generation to generation: there must be random mating, the population must be very large, there can be no movement into or out of the population, there can be no mutations, and there can be no natural selection. Copyright Pearson Prentice Hall The situation in which allele frequencies remain constant in a population is known as genetic drift. the founder effect. genetic equilibrium. natural selection. Copyright Pearson Prentice Hall Which of the following conditions is required to maintain genetic equilibrium in a population? movement in or out of the population random mating natural selection small population Copyright Pearson Prentice Hall Copyright Pearson Prentice Hall Scientists infer that about four billion years ago, Earth cooled and solid rocks formed on its surface. Millions of years later, volcanic activity shook Earth’s crust. About 3.8 billion years ago, Earth’s surface cooled enough for water to remain a liquid, and oceans covered much of the surface. Copyright Pearson Prentice Hall The First Organic Molecules Could organic molecules have evolved under conditions on early Earth? In the 1950s, Stanley Miller and Harold Urey tried to answer that question by simulating conditions on the early Earth in a laboratory setting. Copyright Pearson Prentice Hall Miller and Urey’s Experiment Mixture of gases simulating atmosphere of early Earth Water vapor Spark simulating lightning storms Condensation chamber Cold water cools chamber, causing droplets to form. Liquid containing amino acids and other organic compounds Copyright Pearson Prentice Hall Miller and Urey's experiments suggested mixtures of the organic compounds necessary for life could have come from simpler compounds. Although their simulations were not accurate, experiments with current knowledge yielded similar results. Copyright Pearson Prentice Hall The Puzzle of Life's Origin Evidence suggests that 200–300 million years after Earth had liquid water, cells similar to modern bacteria were common. Formation of Microspheres Microspheres are not cells, but they have selectively permeable membranes and can store and release energy. Evolution of RNA and DNA • • Some RNA sequences help DNA replicate under the right conditions. Some RNA molecules can grow and duplicate themselves suggesting RNA might have existed before DNA. Copyright Pearson Prentice Hall Evolution of RNA and DNA How could DNA and RNA have evolved? Several hypotheses suggest: • Some RNA sequences can help DNA replicate under the right conditions. • Some RNA molecules can even grow and duplicate themselves suggesting RNA might have existed before DNA. Copyright Pearson Prentice Hall The Endosymbiotic Theory: proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms. About 2 billion years ago, prokaryotic cells began evolving internal cell membranes. The result was the ancestor of all eukaryotic cells. Copyright Pearson Prentice Hall Endosymbiotic Theory Ancient Prokaryotes Chloroplast Aerobic bacteria Nuclear envelope evolving Ancient Anaerobic Prokaryote Photosynthetic bacteria Plants and plantlike protists Mitochondrion Primitive Aerobic Eukaryote Copyright Pearson Prentice Hall Primitive Photosynthetic Eukaryote Animals, fungi, and non-plantlike protists Aerobic bacteria Ancient Prokaryotes Nuclear envelope evolving Ancient Anaerobic Prokaryote Copyright Pearson Prentice Hall Prokaryotes that use oxygen to generate energyrich molecules of ATP evolved into mitochondria. Mitochondrion Primitive Aerobic Eukaryote Copyright Pearson Prentice Hall Prokaryotes that carried out photosynthesis evolved into chloroplasts. Chloroplast Photosynthetic bacteria Primitive Photosynthetic Eukaryote Copyright Pearson Prentice Hall Sexual Reproduction and Multicellularity Most prokaryotes reproduce asexually. Asexual reproduction: yields daughter cells that are exact copies of the parent cell. restricts genetic variation to mutations in DNA. Sexual reproduction shuffles genes in each generation. In sexual reproduction: offspring never resemble parents exactly there is an increased probability that favorable combinations will be produced there is an increased chance of evolutionary change due to natural selection Copyright Pearson Prentice Hall
