Introduction to Evolution Biology

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Introduction to EvolutionBiology Ch 16
Where did all organisms come from? Why such
variety?
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Darwins Voyage
Five year voyage around the world collecting
1000s of specimens recording 1000s pages of
notes
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Darwins Observations

• Patterns of Diversity
• Different parts of the world exhibited slightly
  different,
• but similar organisms
• Similar phenotypes
• Africa and South America
• Galapagos Islands
• see next slide!
• Fossil evidence
• Ancient similar organisms?
• Culminate in Theory of Evolution

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Galapagos Tortoises
Different islands different tortoise shells
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Galapagos Finches
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(No Transcript)
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Darwins Influenced by others

• The world is ancient and continually changing
• MUCH older than previously thought
• Continually changes not fixed
• Populations grows faster than the environment can
  support them
• Leads to competition for existing resources
  food, shelter, locations
• Characteristics are inherited, not acquired
  during a lifetime
• Characteristics that allow organisms to survive
  better can reproduce more offspring
• The survival trait gets passed on to offspring

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Darwins Concepts

• Inherited Variation
• Observed that members of any species vary from
  one another in nature
• Observed that breeders are able to get desired
  traits in animals by breeding together those
  animals that exhibit the wanted traits
• The traits randomly occurred in nature
• Named Artificial selection since helped by
  humans

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• Struggle for existence
• Organisms produce more offspring than can
  naturally survive
• Produces a struggle for existence resources,
  space, mates

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• Survival of the Fittest
• Struggle for existence led to only the most fit
  surviving and having offspring
• The ability of an individual to survive and
  reproduce in an environment is fitness
• Anatomical
• Structural
• Behavioral

(The BEST definition)
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• With time, natural selection results in changes
  in the inherited traits of a population. These
  changes can increase a species fitness in an
  environment.

Descent with Modification Over a vey long period
of time, natural selection produces organisms
that have different structures, establish
different ways of surviving, or occupy different
habitats so that organisms today look different
from their ancestors
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Evolution Evidence

• Fossils showed that organisms have been around
  and changing for millions of years
• Geographical distribution of living species
  similarity of species around the world in similar
  environments
• Homologous structures of living organisms
  similar anatomical structures in different
  species led to the idea that they may have had a
  common ancestor
• Similar embryonic development embryos of many
  animals with backbones look similar

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Fossil Evidence
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Geographic Distribution of Living Organisms
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Homologous Body Structures
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Similar embryonic development
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Summary of Darwins Theory

• Individual organisms differ - some of these
  variations are heritable
• Organisms produce more offspring than can
  survive. Some survivors do not reproduce
• Due to overcrowding in an environment, there is
  competition for limited resources
• Each organism has unique characteristics that can
  help it survive or not. Individuals that have
  characteristics that allow them to survive and
  reproduce successfully, produce more offspring
  and pass along these traits to their offspring.
  (Survival of the fittest)
• Species alive today have descended, and changed,
  from ancestors in the distant past (Descent with
  modification)