CHAPTER 13 How Populations Evolve Power Point Lectures

CHAPTER 13 How Populations Evolve Power. Point® Lectures for Essential Biology, Third Edition – Neil Campbell, Jane Reece, and Eric Simon Essential Biology with Physiology, Second Edition – Neil Campbell, Jane Reece, and Eric Simon Lectures by Chris C. Romero Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

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Charles Darwin and The Origin of Species • Charles Darwin’s On the Origin of Species by Means of Natural • Two concepts: “descent with modification” and natural selection. Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

• The basic idea of natural selection is that: - Success in reproduction leads to an accumulation of favored traits in the population over generations - Darwin based this off of: - Species tend to produce excessive numbers of offspring (only a small percentage will survive) - The variation among individuals of a population Example: The evolution of pesticide resistance in hundreds of insect species Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

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• The Darwinian revolution in its historical context 1831 -36: Darwin travels around the world on the HMS Beagle 1837: Darwin begins his notebooks on the origin of species 1844: Darwin writes his essay on the origin of species 1858: Wallace sends his theory to Darwin 1858: The Origin of Species is published Grand Canyon Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

• Jean Baptiste Lamarck was a French naturalist who suggested that the best explanation for the relationship of fossils to current organisms was that life evolves. • He explained evolution as a process of adaption. (evolutionary adaption) • He also proposed that acquired characteristics are inherited. Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

The Voyage of the Beagle • Darwin sailed from Great Britain on the Beagle in December 1831. • Main mission: chart poorly known stretches of the South American coastline. Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

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• On his journey on the Beagle, Darwin – Collected thousands of specimens. – Observed various adaptations in organisms. – The plants and animals living in temperate regions of South America seemed more closely related to species living in tropical regions of that continent than to species living in temperate regions of Europe. Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

• Darwin was intrigued by the geographic distribution of organisms on the Galapagos Islands. Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

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Descent with Modification • Darwin made two main points in The Origin of Species: • Descent of diverse species from common ancestors. • Natural Selection as the mechanism of Evolution Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

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Evidence of Evolution • Fossils • Biogeography • Comparative Anatomy • Comparative Embryology • Molecular Biology Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

The Fossil Record • Over millions of years, deposit piles up and compress older sediments. • If organisms that have been swept into the water die, could be compressed too and may leave imprints into the rock. Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

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Comparative Anatomy • Comparison of body structures between different species. • Certain anatomical similarities show signs of evolutionary history. Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

• Homology: similarity due to common ancestry. • Arms, forelegs, flippers, and wings of different mammals are variations on a anatomical themes that has become adapted to different functions. Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

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Comparative Embryology • Comparative Embryology- The comparison of structures that appear during the development of different organisms Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

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Molecular Biology says: • If two species have genes with nucleotide sequences that match closely, they might have been inherited from a common ancestor. • The greater the number of sequence differences, the less likely the share a common ancestor. Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

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Natural Selection • Darwin studied finches that lived on different Galapagos islands and concluded that: • The finches began to differ from one another because they adapted to their environment. o Different beak shapes (adapted to specific foods). o Might become dissimilar enough to be classified as different species. Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

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Natural Selection in Action • Examples of natural selection include – The evolution of pesticide resistance in hundreds of insect species: a pesticide does not create resistant individuals, but selects for resistant insects that were already present in the population. – The development of antibiotic-resistant bacteria: doctors have recently documented an increase in drug-resistant strains of HIV. Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

Genetic Variation in Populations • An individual’s genome is reflected in their appearance and temperament. Some things cannot be seen. • Not all variation is heritable. Phenotype is made up of the genotype and environmental influences. • Polymorphic: when a population includes two or more forms of a phenotypic characteristic. • Mutations and sexual recombination produce genetic variation. Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings

Sources of Genetic Variation • Mutations: a mutation in a gene may substitute one nucleotide for another, but the change will be harmless if it does not affect the function of the protein the DNA encodes. • Sexual recombination: plants and animals depend on sexual recombination for the genetic variation that makes adaption possible. The two sexual processes of meiosis and random fertilization shuffle alleles and deal them out to offspring in fresh combinations. Copyright © 2007 Pearson Education Inc. , publishing as Pearson Benjamin Cummings