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EVOLUTION CHAPTER 15 • Evolution: the change over time of the genetic composition of populations • Natural Selection: populations of organisms can change over the generations if individuals having certain heritable traits leave more offspring than others (differential reproductive success) • Evolutionary Adapations: a prevalence of inherited characteristics that enhance organisms’ survival and reproduction EVOLUTIONARY HISTORY – Linnaeus - taxonomy - Lyell - uniformitarianism – Hutton - gradualism - Darwin - evolution – Lamarck - evolution - Mendel - inheritance – Malthus - populations - Wallace - evolution – Cuvier - paleontology - Count Buffon - evolution 3 RESISTANCE TO THE THEORY OF EVOLUTION RESISTANCE TO THE THEORY OF EVOLUTION DARWIN’S INFLUENCES Taxonomy matured during mid-eighteenth century Linnaeus believed in: He developed the binomial system of nomenclature System of classification for living things Count Buffon: Wrote 44-volume catalog of all known plants and animals Suggested descent with modification 6 DARWIN’S INFLUENCES Lamarck = First biologist to: Propose evolution Link diversity with environmental adaptation Concluded more complex organisms are descended from less complex organisms: SIMPLE TO COMPLEX Proposed inheritance of acquired characteristics – Lamarckianism 7 Passing on Acquired Traits DESIRE TO CHANGE 9 Use and Disuse HMS BEAGLE VOYAGE • Invited to travel around the world – 1831-1836 (22 years old!) – makes many observations of nature • main mission of the Beagle was to chart South American coastline • While on the voyage of the HMS Beagle in the 1830s, Charles Darwin observed – similarities between living and fossil organisms – the diversity of life on the Galápagos Islands, such as blue-footed boobies and giant tortoises Figure 13.1A FINCHES 13 DARWIN’S INFLUENCES MALTHUS Overpopulation and species control LYELL Earth is subject to slow but continuous cycles of erosion Proposed uniformitarianism, rates and processes of change are constant • Darwin became convinced that the Earth was old and continually changing – He concluded that living things also change, or evolve over generations – He also stated that living species descended from earlier life-forms: descent with modification (originally Buffon and Erasmus Darwin) • All organisms are related through decent from an ancestor that lived in the remote past. DARWIN’S 5 MAJOR CONCLUSIONS 1. Population has Variation 2. Variations may be favorable 3. More offspring are produced than survive 4. Survivors have favorable traits 5. Populations change over time ON THE ORIGIN OF SPECIES • • • ......ALL THIS LEADS TO HIS THEORY OF NATURAL SELECTION and SURVIVAL OF THE FITTEST 1859 Publication Wallace influence WITNESSING NATURAL SELECTION Early 19th century Industrial Revolution Evolution evidence: Fossils • The fossil record shows that organisms have appeared in a historical sequence • Many fossils link early extinct species with species living today – These fossilized hind leg bones link living whales with their landdwelling ancestors Figure 13.2G, H 2006 Fossil Discovery of Early Tetrapod • Tiktaalik – “missing link” from sea to land animals • Evolution evidence: Homologous Structures Similar structure • Similar development • Different functions • Evidence of close evolutionary relationship – recent common ancestor Homologous structures spines leaves succulent leaves needles colored leaves tendrils Evolution evidence: Analogous Structures Separate evolution of structures similar functions similar external form different internal structure & development different origin no evolutionary relationship Don’t be fooled by their looks! Evolution evidence: Comparative Embryology Evolution evidence: Vestigial Structures • Modern animals may have structures that serve little or no function – remnants of structures that were functional in ancestral species – deleterious mutations accumulate in genes for noncritical structures without reducing fitness • snakes & whales — remains of pelvis & leg bones of walking ancestors • eyes on blind cave fish • human tail bone Evolution evidence: Molecular Biology • Similarities in DNA, proteins, genes, and gene products • Common genetic code Closely related species have sequences that are more similar than distantly related species DNA & proteins are a molecular record of evolutionary relationships Fig. 22-20 Evolution evidence: Biogeography • Darwin’s observations of biogeography, the geographic distribution of species, formed an important part of his theory of evolution • Islands have many endemic species that are often closely related to species on the mainland NATURAL SELECTION IN ACTION • Insecticide & drug resistance –insecticide didn’t kill all individuals –resistant survivors reproduce –resistance is inherited –insecticide becomes less & less effective ARTIFICIAL SELECTION • Artificial breeding can use variations in populations to create vastly different “breeds” & “varieties” “descendants” of wild mustard “descendants” of the wolf