OBJECTIVES

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OBJECTIVES     

• The Historical Context for Evolutionary Theory
• Explain the mechanism for evolutionary change
  proposed by Charles Darwin in On the Origin of
  Species.
• Define evolution and adaptation.
• Compare and contrast Aristotles scala naturae to
  Carolus Linnaeus classification scheme.
• Describe the theories of catastrophism,
  gradualism, and uniformitarianism
• Explain the mechanism for evolutionary change
  proposed by Jean-Baptiste de Lamarck. Explain why
  modern biology has rejected Lamarcks theories.   

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The Darwinian Revolution

• Describe how Darwins observations on the voyage
  of the HMS Beagle led him to formulate and
  support his theory of evolution.
• Explain how the principle of gradualism and
  Charles Lyells theory of uniformitarianism
  influenced Darwins ideas about evolution.
• Explain what Darwin meant by descent with
  modification.
• Explain what evidence convinced Darwin that
  species change over time.
• Explain how Linnaeus classification scheme fit
  Darwins theory of evolution by natural
  selection.
• Describe the three inferences Darwin made from
  his observations that led him to propose natural
  selection as a mechanism for evolutionary change.
• Explain how an essay by the Rev. Thomas Malthus
  influenced Charles Darwin.
• Distinguish between artificial selection and
  natural selection.
• Explain why an individual organism cannot evolve.
• Describe the experiments that supported Reznick
  and Endlers hypothesis that differences in
  life-history traits between guppy populations are
  due to selective pressure based on predation.
• Explain how the existence of homologous and
  vestigial structures can be explained by Darwins
  theory of natural selection.
• Explain how evidence from biogeography supports
  the theory of evolution by natural selection.
• Explain the problem with the statement that
  Darwinism is just a theory. Distinguish between
  the scientific and colloquial use of the word
  theory.

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CHAPTER 22DESCENT WITH MODIFICATION
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What is evolution?

• Process that has transformed life on Earth from
  its earliest forms to the enormous diversity of
  today
• Most convincing case for evolution was published
  by Darwin in 1859 On the Origin of Species by
  Means of Natural Selection

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Historical Context of Darwins Life and Ideas
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Western Culture Resisted Evolution

• Plato Idealism Prefect and perceived worlds
• Aristotle Questioned Platos dualism but
  believed species fixed and prevailed for 2000
  years
• Range from simple to complex (scala naturae)
• Judeo Christian view
• Carolus Linnaeus Father of taxonomy (naming and
  classifying organisms) but believed species were
  permanent creations only to support religious
  beliefs

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Cuvier, Fossils, and Catastrophism

• Fossils Relics or impressions of organisms from
  the past, usually preserved in rock
• Fossil record provides evidence that earth has
  had a succession of flora and fauna
• Usually found in sedimentary rock (layers upon
  layers of soil, sand, mud, etc.)

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Cuvier Father of paleontology (study of fossils)

• Realized lifes history was recorded in
  fossil-containing strata and documented
  succession of fossil species in Paris Basin
• Each stratum characterized by a unique set of
  fossil species oldest stratum most dissimilar
  to modern life forms
• From stratum to stratum, new species appeared and
  others disappeared

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Catastrophism Theory that major changes in the
Earths crust are the result of catastrophic
events rather than from gradual processes of
change

• Periodic localized catastrophes resulted in mass
  extinctions
• Following extinctions, region becomes repopulated
  by foreign species immigrating from other areas

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Geological theories

• Gradualism James Hutton profound change is
  the product of slow, continuous processes

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• Uniformitarianism Theory that geological
  processes are uniform and have operated from the
  origin of Earth to present (Charles Lyell)

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Lamark

• Proposed Mechanism By Which Organisms Evolved
• Use and disuse Those body organs used
  extensively to cope with the environment become
  larger and stronger while those not used
  deteriorate
• Inheritance of acquired characteristics
  modifications an organism acquired during its
  lifetime could be passed along to its offspring

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Voyage of the Beagle

• While ships mission was to chart South America
  (SA) coastline, Darwin made observations
• SA flora and fauna were distinct from European
  flora and fauna
• Temperate species closer to tropical species than
  temperate species in Europe
• SA fossils were distinctly SA
• Most animal species on Galapagos are unique to
  those islands, but resemble species living on SA
  coastline

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Origin of Species

• Descent with Modification (evolution)
• Unity in life with all organisms related through
  descent from ancestral population
• Diverse modifications (adaptations) accumulated
  over millions of years as descendants moved into
  various habitats

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Darwins view of Evolution Branches at the end
demonstrate the diversity of the species
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Natural Selection and Adaptations

• Observation 1 All species overproduce

Flowers or Seeds
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• Observation 2 Most populations are normally
  stable except for seasonal fluctuations
• Observation 3 Natural resources are limited
• Inference 1 Struggle for existence allows for
  survival of only a fraction of offspring
• Food, water, and space

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• Observation 4 Variation exists in population
• No spot on the ladybugs below is the same as
  another

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• Observation 5 Much of this variation is
  heritable
• Inference 2 Those individuals best fit to
  survive will produce more offspring than those
  less fit to survive
• Inference 3 Unequal ability of individuals to
  survive and reproduce will lead to a gradual
  change in populations, with favorable
  characteristics accumulating over generations

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• Gradualism Evolution occurs by a gradual
  accumulation of small changes and mechanism of
  modification is natural selection
• Populations Group of interbreeding individuals
  belonging to a particular species and geographic
  location are the smallest unit that can evolve

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Evidence

• Biogeography Geographical distribution of
  species
• Islands have many endemic species which are
  closely related to species on the nearest
  mainland or neighboring island

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The Fossil Record

• Many transition fossils have been found that link
  ancestral species to modern forms
• Fossil record supports other kinds of evidence
  about phylogenetic tree
• Prokaryotes are placed as ancestors of all life
  by evidence from cell biology, biochemistry, and
  molecular biology
• Fossil evidence shows chronological appearance of
  vertebrates fishes, amphibians, reptiles, then
  birds, and mammals

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Comparative Anatomy Anatomical similarities
among species grouped in the same taxonomic
category as a reflection of common descent

• Homologous structures similar because of common
  ancestry

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Vestigial organs rudimentary structures of
marginal or no use to an organism

• In the early 1900s these structures were
  considered useless. Today there is at least 1
  known function for each.

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• Comparative Embryology Closely related
  organisms go through similar stages in their
  embryonic development gill slits develop into
  eustachian tubes in humans

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Molecular Biology An organisms hereditary
background is reflected in its genes and their
protein products

• Sibling similarity
• Two closely related species should share a great
  proportion of their genes and proteins