CHAPTER 23 LECTURE SLIDES Prepared by Brenda Leady University of Toledo To run the animations you must be in Slideshow View. Use the buttons on the animation to play, pause, and turn audio/text on or off. Please note: once you have used any of the animation functions (such as Play or Pause), you must first click in the white background before you advance the next slide. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Biological evolution Heritable change in one or more characteristics of a population or species from one generation to the next Viewed on a small scale relating to changes in a single gene in a population over time – microevolution Viewed on a larger scale relating to formation of new species or groups of species – macroevolution

Species Group of related organisms that share a distinctive form Among species that reproduce sexually, members of the same species are capable of interbreeding to produce viable and fertile offspring Population Members of the same species that are likely to encounter each other and thus have the opportunity to interbreed

Theory of evolution Empirical thought Relies on observation to form an idea or hypothesis, rather than trying to understand life from a non-physical or spiritual point of view Shift toward empirical thought encouraged scholars to look for the basic rationale behind a given process or phenomenon

Extended by Carolus Linnaeus Mid- to late-1600s, John Ray was the first to carry out a thorough study of the natural world Developed an early classification system Modern species concept Extended by Carolus Linnaeus Neither proposed that evolutionary change promotes the formation of new species

George Buffon says life forms change over time Late 1700s, small number of European scientists suggest life forms are not fixed George Buffon says life forms change over time Jean-Baptiste Lamarck realized that some animals remain the same while others change Believed living things evolved upward toward human “perfection” Inheritance of acquired characteristics Giraffe neck example

Charles Darwin British naturalist born in 1809 Theory shaped by several different fields of study Geology Economics Voyage of the Beagle

Uniformitarism hypothesis from geology Slow geological processes lead to substantial change Earth was much older than 6,000 years Thomas Malthus, an economist, says that only a fraction of any population will survive and reproduce

HMS Beagle (1831-1836) Darwin’s ideas were most influenced by his own observations Struck by distinctive traits of island species that provided them ways to better exploit their native environment Galapagos Island finches Saw similarities in species yet noted that differences that provided them with specialized feeding strategies

Formulated theory of evolution by mid-1840s Spent several additional years studying barnacles 1856, began writing his book 1858, Alfred Wallace sends Darwin an unpublished manuscript proposing many of the same ideas Darwin’s and Wallace’s papers published together 1859, Darwin’s The Origin of the Species is published detailing his ideas with observational support

Descent with modification Evolution based on Variation within a given species Traits heritable – passed from parent to offspring Genetic basis not yet known Natural selection More offspring produced than can survive Competition for limited resources Individual with better traits flourish and reproduce

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Surviving birds that reproduce Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Surviving birds that reproduce

Surviving birds that reproduce Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Surviving birds that reproduce

Copyright © The McGraw-Hill Companies, Inc Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Surviving birds that reproduce

The Grants Have Observed Natural Selection in Galapagos Finches Since 1973, the Grants have studied natural selection Focused much of their work on Daphne Major – moderately isolated, undisturbed habitat and resident finches Compared beak sizes of parents and offspring over many years Birds with larger beaks survived better during drought years In the year after drought, average beak depth increases