1. CHAPTER 23 LECTURE SLIDES
Prepared by
Brenda Leady
University of Toledo
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2. 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

3. 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

4. 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

5. 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

6. 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

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

8. 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

9. HMS Beagle ( )
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

12. 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

13. 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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16. Surviving birds that reproduce
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Surviving birds that
reproduce

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

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

19. 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