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Darwin and Evolution Chapter 17 History of Evolutionary Thought Prior to Darwin, most people had a mindset determined by deep-seated beliefs held to be intractable truths Biology during preceding century had slowly begun to accept the idea of evolution

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history of evolutionary thought
History of Evolutionary Thought
  • Prior to Darwin, most people had a mindset determined by deep-seated beliefs held to be intractable truths
    • Biology during preceding century had slowly begun to accept the idea of evolution
    • Living things share common characteristics due to common ancestry

Mader: Biology, 9th Ed.

mid eighteenth century
Mid-Eighteenth Century

Taxonomy was an important endeavor during mid-eighteenth century

  • Carolus Linnaeus
    • Special creation – each species has an ideal structure and function
    • Fixity of species – each species had a place in the scala naturae(sequential ladder of life)

Mader: Biology, 9th Ed.

mid eighteenth century4
Mid-Eighteenth Century

Count Buffon wrote 44-volume natural history describing all known plants and animals

  • Provided evidence of descent with modification
  • Influences of the environment, migration, geographical isolation, and the struggle for existence

Mader: Biology, 9th Ed.

mid eighteenth century5
Mid-Eighteenth Century

Erasmus Darwin

  • Suggested common descent based on:
    • Changes undergone by animals during development
    • Artificial selection by humans
    • The presence of vestigial organs

Mader: Biology, 9th Ed.

late eighteenth century
Late Eighteenth Century

George Cuvier

  • First to use comparative anatomy to develop a system of classification
  • Founded Paleontology
  • Proposed Catastrophism
    • Hypothesized local catastrophes had occurred whenever a new strata showed a new mix of fossils
    • After each catastrophe, a region was repopulated by species from surrounding areas.

Mader: Biology, 9th Ed.

late eighteenth century7
Late Eighteenth Century

Lamarck

  • First biologist to believe evolution occurs
  • First to link diversity with environmental adaptation
  • Concluded more complex organisms are descended from less complex organisms
  • Inheritance of acquired characteristics (Lamarckianism)
    • Giraffes stretch necks and then pass on long necks to offspring

Mader: Biology, 9th Ed.

late eighteenth century8
Late Eighteenth Century

Charles Lyell

  • Supported a theory that the earth was subject to slow but continuous cycles of erosion and uplift
  • Uniformitarianism rates and processes of change are constant

Mader: Biology, 9th Ed.

darwin s theory of evolution
Darwin’s Theory of Evolution

Mader: Biology, 9th Ed.

darwin s theory of evolution10
Darwin’s Theory of Evolution
  • Occurrence of Descent
    • Darwin was not convinced of uniformitarianism, but did believe the earth was very old
    • Enough time for descent with modification

Mader: Biology, 9th Ed.

biogeography
Biogeography
  • Biogeography is the study of the geographic distribution of lifeforms on earth
    • Darwin saw how similar species in similar habitats
    • Reasoned related species could be modified according to the environment

Mader: Biology, 9th Ed.

gal pagos islands
Galápagos Islands
  • Tortoises
    • Darwin noticed tortoise neck length varied from one island to next
    • Proposed that tortoise speciation on islands could be correlated with a difference in vegetation among the islands

Mader: Biology, 9th Ed.

gal pagos islands13
Galápagos Islands
  • Finches
    • Darwin observed different species of finches on various islands
    • Speculated that all the different types of finches could have descended from a single type of mainland finch

Mader: Biology, 9th Ed.

natural selection and adaptation
Natural Selection and Adaptation
  • Natural selection proposed as a driving mechanism of evolution caused by environmental selection of organisms most fit to reproduce, resulting in adaptation

Mader: Biology, 9th Ed.

three preconditions for natural selection
Three Preconditions for Natural Selection
  • Individuals have heritable variations
  • Many more individuals are produced each generation than the environment can support
  • Some individuals have adaptive characteristics enabling increased survival and reproduction

Mader: Biology, 9th Ed.

two consequences of natural selection
Two Consequences of Natural Selection
  • Increasing proportion of succeeding generations have these characteristics
  • Populations become adapted to their local environment

Mader: Biology, 9th Ed.

organisms have variations
Organisms Have Variations
  • Darwin emphasized members of a population vary in their functional, physical, and behavioral characteristics
    • Believed variations were essential
    • New variations as likely to be helpful as harmful
    • Heritable variations allow adaptation to the environment

Mader: Biology, 9th Ed.

variation in a population
Variation in a Population

Mader: Biology, 9th Ed.

organisms struggle to exist
Organisms Struggle to Exist
  • Malthus stressed the reproductive potential of human beings
    • Proposed death and famine were inevitable due to rapid population growth
    • Each generation has the same reproductive potential as the previous generation
    • Constant struggle for existence

Mader: Biology, 9th Ed.

organisms differ in fitness
Organisms Differ in Fitness
  • Fitness is the relative reproductive success of an individual
    • Most-fit individuals capture a disproportionate amount of resources
    • In nature, interactions with the environment determine which members of a population reproduce to a greater degree
      • Artificial Selection

Mader: Biology, 9th Ed.

artificial selection
Artificial Selection

Mader: Biology, 9th Ed.

artificial selection in plants
Artificial Selection in Plants

Mader: Biology, 9th Ed.

organisms become adapted
Organisms Become Adapted
  • An adaptation is a trait that helps an organism become more suited to its environment
    • Product of natural selection

Mader: Biology, 9th Ed.

the evidence of evolution
The Evidence of Evolution
  • Fossil Evidence
    • Fossil record is the history of life recorded by remains from the past
    • Documents a succession of life forms from the simple to the more complex
    • Sometimes the fossil record is complete enough to allow a trace of the evolutionary history of an organism

Mader: Biology, 9th Ed.

transitional fossils
Transitional Fossils

Mader: Biology, 9th Ed.

biogeographical evidence
Biogeographical Evidence
  • Distributions of many plants and animals across earth consistent with hypothesis that when forms are related, they evolved in one locale and then spread to accessible regions
    • Marsupials

Mader: Biology, 9th Ed.

slide28

Biogeography

Mader: Biology, 9th Ed.

anatomical evidence
Anatomical Evidence
  • Darwin was able to show a common descent hypothesis offers a plausible explanation for anatomical similarities among organisms
    • Despite dissimilar functions, all vertebrate forelimbs contain the same sets of bones in similar ways

Mader: Biology, 9th Ed.

anatomical evidence30
Anatomical Evidence
  • Homologous Structures are anatomically similar because they are inherited from a common ancestor
  • Analogous Structures serve the same function, but are not constructed similarly, and do not share a common ancestor
  • Vestigal Structures are fully-developed anatomical structures developed in one group of organisms, but reduced, and may have no function, in similar groups

Mader: Biology, 9th Ed.

biochemical evidence
Biochemical Evidence
  • Almost all living organisms
    • Use the same basic biochemical molecules
    • Utilize same DNA triplet code
    • Utilize same 20 amino acids in their proteins
  • When the degree of similarity in DNA base sequences are compared, the data suggest common descent
    • When very similar, suggest recent common descent
    • When more different, suggest more ancient common descent

Mader: Biology, 9th Ed.

biochemical differences
Biochemical Differences

Mader: Biology, 9th Ed.

slide35
Mader: Biology, 9th Ed.

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