Development of Evolutionary Thought

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Development of Evolutionary Thought
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Isnt evolution just a theory?

• Scientific theories are explanations that are
  based on lines of evidence, enable valid
  predictions, and have been tested in many ways.

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Evolve change over time
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What is Evolution?

• Evolution - a change in the genetic composition
  of a population over time.

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Paleontology Evolution

• Older layers of sedimentary rock (the layers on
  the bottom) contain fossil species very
  dissimilar from modern life.
• Each layer (stratum) is characterized by a unique
  group of fossil species.
• As you move upward through the layers, you find
  species more and more similar to modern life.

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James Hutton - 1795

• A Scottish geologist
• proposed that it was possible to explain the
  various landforms by looking at mechanisms
  currently operating in the world
• Proposed that the earth was much more than a few
  thousand years old

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Jean Baptiste Lamarck

• Theory of evolution in 1809
• mechanism
• use and disuse - the idea that the parts used the
  most grow stronger the parts that dont get used
  deteriorate
• inheritance of acquired characteristics - the
  modifications that an organism acquires during
  its lifetime can be passed along to its offspring
• recognized adaptation to environment as a primary
  product of evolution

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Charles Darwin (1809-1882)

• Father of modern
• evolutionary theory
• Born in England
• HMS Beagle
• Galapagos Islands

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The Galapagos Finches
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What is an adaptation?

• An inherited characteristic that increases an
  organisms ability to survive and reproduce in
  its specific environment.

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Darwins Observations

• Darwin noticed that every bird on the Galapagos
  Islands was a modified finch.
• The only differences in the birds were their
  beaks and what they ate.
• These finches looked very similar to one type on
  South American continent, but none of these were
  found in S.A.
• How did one species change into a different
  species?

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He wrote On The Origin of Species (1859) after
20 years of study.
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Darwins Four Postulates

• Individuals within a population vary in their
  traits.
• Some of these traits are heritable.
• More offspring are produced than can survive
  because of limited resources.
• Individuals with advantageous traits will survive
  and reproduce.

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What is natural selection?

• Natural selection - a population of organisms can
  change over generations if individuals having
  certain heritable traits leave more offspring
  than others
• Natural selection is the mechanism by which
  evolution is proposed to occur

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What is artificial selection?

• Nature provides the variation among different
  organisms, and humans select variations that they
  find useful.
• Example breeding cows, horses, hogs
• Darwin used this to help support his case for
  natural selection.

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Descent with modification

• the history of life is like a tree, with multiple
  branching and re-branching from a common trunk
  all the way to the tips of the youngest twigs
• most branches of evolution are dead ends about
  99 of all species that have ever lived are
  extinct

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Figure 22.7 Descent with modification
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Survival of the Fittest

• Another name for Darwins theory of natural
  selection.

• Biologists use the word fitness to describe how
  good a particular genotype is at leaving
  offspring in the next generation relative to how
  good other genotypes are at it.

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Mechanisms of Evolution
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Natural Selection Survival of the Fittest

• (already discussed with Darwin)

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Modern Ideas

• Darwin Mendels work and the work of others,
  have lead to modern ideas about evolution.
• Another mechanism of evolution is Genetic Drift
  (random changes in genes) which occurs through
  natural selection.

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Modern Ideas

• Speciation formation of new species is due to
  gradual genetic changes, and that large scale
  evolution is the result of a lot of small scale
  evolution.
• Microevolution process responsible for the
  variations that exist within a species, or a
  change in the allele frequency.

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Modern Ideas

• Macroevolution evolution that occurs between
  species.
• Examples the separation of a species to form two
  distinct species or the development of a new
  species from many small changes within an
  existing species

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Gene Flow

• The change in occurrence of genes in a
  population. This occurs when an individual leaves
  a population (emigration) or new individual joins
  a population (immigration).

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Genetic Drift

• Random changes in the occurrence of genes through
  chance events.
• Can occur when a few individuals of a population
  break off from the original group and start their
  own population (founder effect).
• Large number of population is killed due to
  disease, starvation, natural disaster, etc.
  (bottle necking)

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Punctuated Equilibrium

• Darwin felt that biological change was slow and
  steady as indicated in the fossil record.
• Modern scientists see that this pattern does not
  always hold. (Darwins finches)
• The term punctuated equilibrium is used to
  describe a pattern of long, stable periods
  interrupted by brief periods of more rapid
  change. This is still controversial today.

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Evidence of Evolution
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Fossil Evidence

• Fossils provided a detailed record of evolution.
• Fossils formed in different layers of rock were
  evidence of gradual change over time.

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Homologous Body Structures

• Structures in different species that may perform
  different functions but are similar because of
  their common ancestry
• Vestigial organs - structures of no apparent
  function to an organism leftover from ancestry
  ex - snakes have leg pelvis bones

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Figure 22.14 Homologous structures anatomical
signs of descent with modification
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More homology

• Molecular homology - similarity in DNA sequence
  between an ancestor and its progeny
• Embryological homology - similarities only
  apparent in embryological development
• ex all vertebrate embryos have pharyngeal
  pouches which later become gills or Eustachian
  tubes

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Patterns of Evolution
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Adaptive Radiation

• When a single species or a small group of species
  has evolved into several different forms that
  live in different ways.
• Example Darwins finches (more than a dozen
  evolved from a single species)

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Convergent Evolution

• Explains how unrelated species can develop
  similar characteristics
• Porpoise (mammal) Shark (fish)
• Unrelated animals, but share similar
  characteristics to suit their environment

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Analogous structures

• Show similarity in structure based on adaptation
  for the same function, not common descent.

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Divergent Evolution

• Suggests that many species develop from a common
  ancestor
• Penguins (wings for swimming) vultures (wings
  for flying)
• Both are birds, diverged from a common ancestor

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Co-evolution

• When two or more organisms in an ecosystem evolve
  in response to each other.
• Example Flowers and their pollinators

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Camouflage an animal looks like its environment.

• http//rainforests.mongabay.com/0306.htm

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Mimicry- when animals have coloring and markings
to look like another animal