The Theory of Evolution by Natural Selection Charles Darwin More than anyone else in the history of science, Charles Darwin provided us with an answer to “why are there so many species”?

Western Historical Context Aristotle (384-322 B.C.) – Greek philosopher Species are permanent, perfect, immutable Dominant world view for > 2000 yr See timeline Fig. 22.2

Western Historical Context A.D. – Natural Theology (Creationism) Species are permanent, perfect, immutable A.D. = anno Domini, “the year of our Lord”. See timeline Fig. 22.2

Western Historical Context Carolus Linnaeus (1707-1778) Swedish physician & botanist whose passion was taxonomy Developed a hierarchical classification scheme & binomial nomenclature Karl von Linne (Carolus Linnaeus) = Swedish physician & botanist. Taxonomy = branch of biology concerned with naming and classifying organisms. Binomial composed of genus and specific epithet that refers to one species. See timeline Fig. 22.2

Western Historical Context Carolus Linnaeus (1707-1778) Canis = genus lupus = specific epithet that refers to one species in the genus Canis The binomial is always italicized or underlined, the genus name is always capitalized, and the specific epithet is always lower case “King Philip Came Over For Gumbo Sunday” See Fig. 25.8

Western Historical Context Georges Cuvier (1769-1832) French anatomist who largely developed paleontology, the study of fossils Geoges Cuvier = French anatomist. Paleontology – The study of fossils. See timeline Fig. 22.2

Western Historical Context Georges Cuvier (1769-1832) Deeper strata contain older taxa See timeline Fig. 22.2

Western Historical Context Georges Cuvier (1769-1832) Preferred hypothesis for profound geologic change = catastrophism See timeline Fig. 22.2

Western Historical Context James Hutton (1726-1797) Scottish geologist who offered an alternative to catastrophism Preferred hypothesis for profound geologic change = gradualism James Hutton = Scottish geologist. Profound changes are the cumulative product of slow but continuous processes; e.g., laying down strata and then carving out river valleys. See timeline Fig. 22.2

Western Historical Context Charles Lyell (1797-1875) Scottish geologist who incorporated Hutton’s gradualism into the theory of uniformitarianism Charles Lyell = Scottish geologist. See timeline Fig. 22.2

Western Historical Context Charles Lyell (1797-1875) Uniformitarianism – geological processes & rates today are those that also operated in antiquity Charles Lyell = Scottish geologist. See timeline Fig. 22.2

Western Historical Context Charles Lyell (1797-1875) Uniformitarianism – suggested that the Earth is > 6000 yr old Charles Lyell = Scottish geologist. See timeline Fig. 22.2

Western Historical Context Jean Baptiste Lamarck (1744-1829) Invertebrate Curator of the Natural History Museum in Paris One of the 18th & 19th centuries’ biologists who hypothesized that traits of species are not immutable, i.e., they can evolve Jean Baptiste Lamarck = Invertebrate Curator of Natural History Museum in Paris. See timeline Fig. 22.2

Western Historical Context Jean Baptiste Lamarck (1744-1829) Hypothesized mechanism of evolution: Use & disuse alters traits; inheritance of acquired characters results in adaptations to environmental conditions Jean Baptiste Lamarck = Invertebrate Curator of Natural History Museum in Paris. See timeline Fig. 22.2

Western Historical Context Thomas Malthus (1766-1834) English demographer Hypothesis: Plants and animals are capable of producing far more offspring than resources can support; the “struggle for existence” (e.g., famine, war) is an inescapable consequence English demographer and political economist. See timeline Fig. 22.2

Western Historical Context Within this context, Charles Darwin (1809-1882) served as Ship’s Naturalist on the HMS Beagle’s circumnavigation of the globe (1831-1836) England EUROPE NORTH AMERICA Galápagos Islands Darwin in 1840, after his return SOUTH Cape of Good Hope Cape Horn Tierra del Fuego AFRICA HMS Beagle in port AUSTRALIA Tasmania New Zealand PACIFIC OCEAN Andes ATLANTIC

Galapagos Islands, Ecuador

Galapagos Islands, Ecuador

Galapagos Islands, Ecuador

Galapagos Islands, Ecuador

Darwin was a good observer of both wild and domesticated organisms (e Darwin was a good observer of both wild and domesticated organisms (e.g., birds)

Darwin was a good observer of both wild and domesticated organisms (e Darwin was a good observer of both wild and domesticated organisms (e.g., birds)

Western Historical Context Charles Darwin (1809-1882) English gentleman who conceived of natural selection as the principal mechanism of adaptive evolution See timeline Fig. 22.2

Western Historical Context Alfred Russel Wallace (1823-1913) English biologist who also (independently) conceived of natural selection as the principal mechanism of adaptive evolution See timeline Fig. 22.2

Western Historical Context Lyell presented the independently derived hypothesis to the Linnaean Society of London on July 1, 1858

Western Historical Context Charles Darwin (1809-1882) The Origin of Species (1859)

The Origin of Species Final paragraph: “It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us… There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed laws of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.” Darwin recognizes the mystery of the origin of life, but provides a key mechanistic explanation for the continual, ever-present process of evolution.

Darwinian Theory of Evolution Descent with modification Descent implies common ancestry Modification to better suite the environment = adaptation “Descent with modification” is evolution by natural selection in Darwin’s own words. 150 years of rigorous research have proven that Darwin hypothesis was essentially correct; his hypothesis has become the “Darwinian Theory of Evolution”. Natural selection is the principal process that drives adaptive evolution See Fig. 22.7

Darwinian Theory of Evolution Organisms have enormous potential for population increase, but the potential is rarely reached Generalized sigmoidal population growth curve

Potential for rapid population growth when resources are not limiting Resource availability generally limits population size Competition for resources (“struggle for existence”) Phenotypic variability (morphology, physiology, behavior, etc.) Natural Selection: Survival and reproduction of the “fittest” individuals Some variability results from heritable differences Evolution by natural selection in modern terms. See next lecture (Chapt. 23) for a modification of this! Adaptive evolution: A change in the phenotypic constitution of a population owing to selection on heritable variation among phenotypes

inheritance from selected population Lamarckism Use Inheritance of acquired characteristics Darwinism Genetic inheritance from selected population Natural selection Generation 1 Generation 2

Evidence for the Theory of Evolution by Natural Selection Darwin used artificial selection to illustrate the modifying potential of selection

Evidence for the Theory of Evolution by Natural Selection Darwin used artificial selection to illustrate the modifying potential of selection

Evidence for the Theory of Evolution by Natural Selection Darwin used artificial selection to illustrate the modifying potential of selection

Rapid changes in populations under strong selection Evidence for the Theory of Evolution by Natural Selection Rapid changes in populations under strong selection E.g., pesticide resistance

Evidence for the Theory of Evolution by Natural Selection Homologous traits (a.k.a. characters, attributes) = traits in different species that arose from the same ancestral trait (may or may not have similar function) Human Cat Whale Bat See Fig. 22.14

Evidence for the Theory of Evolution by Natural Selection Even when homologies are not obvious in adults, they may be quite apparent in embryonic stages Lemur Pig Human Which one is the human?

Evidence for the Theory of Evolution by Natural Selection Analogous traits = traits in different species that have similar function, but arose from different ancestral traits

To distinguish homologous vs To distinguish homologous vs. analogous traits, the relatedness of the organisms doesn’t matter as much as the evolutionary history of the traits themselves

Evidence for the Theory of Evolution by Natural Selection Analogous traits = traits in different species that have similar function, but arose from different ancestral traits

These examples happen to be homologous leg and foot bones Evidence for the Theory of Evolution by Natural Selection Vestigial organs = remnants of organs that had important functions in ancestors These examples happen to be homologous leg and foot bones

Evidence for the Theory of Evolution by Natural Selection Vestigial organs = remnants of organs that had important functions in ancestors

Biochemical homologies Evidence for the Theory of Evolution by Natural Selection Biochemical homologies Common use of DNA, RNA, amino acids, ribosomes, genetic code, ATP, electron carriers, electron transport system, etc.