Darwin and Evolution
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Outline. History of Evolutionary Thought Darwin’s Theory of Evolution Earth very old Descend with change from a common ancestor Adaptation to a changing environment The Evidence of Evolution Fossil Biogeographical Anatomical Biochemical. Voyage of the HMS Beagle. Charles Darwin at 31.

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Outline 1725836

Darwin and Evolution


Outline

Outline

  • History of Evolutionary Thought

  • Darwin’s Theory of Evolution

    • Earth very old

    • Descend with change from a common ancestor

    • Adaptation to a changing environment

  • The Evidence of Evolution

    • Fossil

    • Biogeographical

    • Anatomical

    • Biochemical


Voyage of the hms beagle

Voyage of the HMS Beagle


Charles darwin at 31

Charles Darwin at 31


History of evolutionary thought

History of Evolutionary Thought

  • Prior to Darwin

    • View of nature determined by deep-seated beliefs

    • Held to be intractable truths

    • Biology thought had slowly begun to accept

      • Various ideas of evolution

      • Similarities between living things reflect recent common ancestry

      • Dissimilarities between living things reflect ancient common ancestry


Evolutionary thought before darwin

Evolutionary Thought before Darwin


Mid eighteenth century

Mid-Eighteenth Century

  • Taxonomy matured during mid-eighteenth century

    • Linnaeus believed in:

      • The fixity of species

      • That each species had:

        • An ideal structure and function, and

        • A place in the scala naturae (scale of complexity)

    • Count Buffon:

      • Wrote 44-volume catalog of all known plants and animals

      • Suggested descent with modification


Late eighteenth century

Late Eighteenth Century

  • Cuvier:

    • First to use comparative anatomy to develop a system of classification

    • Founded Paleontology

    • Proposed Catastrophism

      • Local catastrophes in past had caused later strata to have a new mix of fossils

      • After each catastrophe, the region was repopulated by species from surrounding areas


Late eighteenth century1

Late Eighteenth Century

  • Lamarck:

    • First biologist to:

      • Propose evolution

      • Link diversity with environmental adaptation

    • Concluded more complex organisms are descended from less complex organisms

    • Proposed inheritance of acquired characteristics – Lamarckianism

  • Charles Lyell:

    • Earth is subject to slow but continuous cycles of erosion and uplift

    • Proposed uniformitarianism, rates and processes of change are constant


Formation of sedimentary rock

Formation of Sedimentary Rock


Darwin s theory of evolution

Darwin’s Theory of Evolution

  • Geological observations consistent with those of Hutton & Lyell

  • Biogeographical observations:

    • The study of the geographic distribution of life forms on earth

    • Darwin saw similar species in similar habitats;

    • Reasoned related species could be modified according to the environment


A glyptodont and a giant sloth

A Glyptodont and a Giant Sloth


The patagonian hare dolichotis patagonium

The Patagonian Hare,Dolichotis patagonium


Gal pagos islands

Galápagos Islands

  • Tortoises

    • Darwin observed tortoise neck length varied from island to island

    • Proposed that speciation on islands correlated with a difference in vegetation

  • Finches

    • Darwin observed many different species of finches on various islands

    • Speculated they could have descended from a single pair of mainland finch


Gal pagos tortoises geochelone

Galápagos Tortoises, Geochelone


Gal pagos finches

Galápagos Finches


Natural selection and adaptation

Natural Selection and Adaptation

  • Individuals have heritable variations

  • More individuals produced each generation than environment can support

  • Some individuals have adaptive characteristics

    • Enables increased survival and reproduction

    • Increasing proportion of succeeding generations will have these characteristics

  • Populations become adapted to their local environment through change in individuals


Variation in a population

Variation in a Population


Organisms have variations

Organisms Have Variations

  • Darwin emphasized that individuals from a population vary in their:

    • Functional characteristics

    • Physical characteristics

    • Behavioral characteristics

  • Proposed that these variations:

    • Are essential

    • Allow adaptation to the environment over time


Artificial selection of animals

Artificial Selection of Animals


Artificial selection of plants

Artificial Selection of Plants


Organisms struggle to exist

Organisms Struggle to Exist

  • Malthus

    • Each generation has the same reproductive potential as the previous generation

      • Reproductive potential is greater than environment can support

      • Death, disease, and famine were inevitable if population were to have stability

    • Individuals experience a constant struggle for survival


Organisms differ in fitness

Organisms Differ in Fitness

  • Fitness is the relative reproductive success of an individual

    • The most-fit individuals in a population capture a disproportionate share of goodies

    • Interactions with the environment determine which individuals reproduce the most

  • Adaptation

    • Changes that help a species become more suited to its environment

    • Product of natural selection


Transitional fossils

Transitional Fossils


The evidence of evolution anatomical

The Evidence of Evolution:Anatomical

  • Vertebrate forelimbs:

    • Homologous - All contain the same sets of bones in similar ways

    • Yet they are modified extensively to meet various adaptive needs

    • Darwin interpreted this as support for a hypothesis of common descent

  • Embryological development

    • All vertebrate embryos have:

    • A postanal tail and

    • Paired pharyngeal (gill) pouches


Biogeography

Biogeography


The evidence of evolution anatomical1

The Evidence of Evolution:Anatomical

  • Homologous Structures:

    • Anatomically similar because they are inherited from a common ancestor

    • May be functionally similar or not

  • Analogous Structures:

    • Serve the same function

    • Not constructed similarly

    • Do not share a common ancestor

  • Vestigal Structures:

    • Fully-developed anatomical structures

    • Reduced or obsolete function


Significance of homologous structures

Significance of Homologous Structures


Significance of developmental similarities

Significance of Developmental Similarities


Vestigial limbs in whales

Vestigial Limbs in Whales


The evidence of evolution fossil biogeographical

The Evidence of Evolution:Fossil & Biogeographical

  • Fossil Evidence

    • Fossils record the history of life from the past

    • Document a succession of life forms from the simple to the more complex

    • Sometimes the fossil record is complete enough to show descent from an ancestor

  • Biogeographical

    • Distributions of plants and animals across earth

    • Consistent with origin in one locale and then spread to accessible regions


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

  • DNA base-sequence differences:

    • When very similar, suggest recent common descent

    • When more different, suggest more ancient common descent


Significance of biochemical differences

Significance ofBiochemical Differences


Review

Review

  • History of Evolutionary Thought

  • Darwin’s Theory of Evolution

    • Earth very old

    • Descend with change from a common ancestor

    • Adaptation to a changing environment

  • The Evidence of Evolution

    • Fossil

    • Biogeographical

    • Anatomical

    • Biochemical


Outline 1725836

Darwin and Evolution


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