The Theory of Evolution

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Chapter 13

• The Theory of Evolution

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Jean Baptist de Lamarck

• Theory of Acquired Characteristics
• features increased in size because of use or
  reduced in size because of disuse!
• these acquired traits are passed to offspring
• change in species are due to the physical
  conditions of life ( environment)
• NOT TRUE!

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Charles Darwin

• A Naturalist who, in 1831, traveled on the HMS
  Beagle for a five year expedition to collect,
  study, and store biological specimens discovered.
• Father of the Theory of Evolution

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Alfred Russel Wallace

• Studied the birds of Malaysia and hypothesized
  the same Theory of Natural Selection as Darwin.
• Darwin then published his earlier works.

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Darwins Pigeons

• Artificial Selection - By breeding pigeons that
  had a desirable trait, the offspring would carry
  these same traits.
• Natural Selection - Nature selects or chooses
  which traits in an organism will be passed on to
  future generations.

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Darwins Theory of Natural Selection

• 1. Variations exist within populations.
• 2. Some variations are more advantageous than
  others.
• 3. Organisms produce more offspring than can
  survive.
• 4. The fittest survive and reproduce! Thus the
  species modifies itself over time. (Nature
  selects who lives.)

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The Galapagos Islands

• Darwin observed islands with great biodiversity.
• Organisms were best suited for their own
  particular climate.

• Island organisms seemed to have adapted to each
  particular island climate.
• After 22 years of data analysis, Darwin formed
  his Theory of Adaptation by Natural Selection.

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Adaptation

• Adaptation is the evolutionary process whereby a
  population becomes better suited to its habitat.
  This process takes place over many generations.
• Populations adapt as the environment changes.
• Types of Adaptions
• Structural-outward look, appearance, body part
• Behavioral-mating, food gathering
• Physiological-internal to the organism

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Structural Adaptations

1. Mimicry-A structural adaptation that provides
   protection by enabling an organism to copy
   another species.

(Monarch, original/poisonous and Viceroy,
copy/harmless) --coloring is a warning to other
organisms Stay away!
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2. Camouflage- A structural adaptation that
enables the organism to blend in with its
environment. ( Peppered Moths and Leaf Bugs)
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Behavioral Adaptations

• Behavioral adaptations help an organism to
  enhance survival or reproduction by making a
  change to their behavior.
• Mobbing birds- the mob may protect their young
  from predators by confusing them.
• Migrating waterfowl- have access to abundant food
  all year round by migrating.
• Mating Calls- Certain species of female frogs
  prefer males with long breeding calls, because
  males with long calls have better breeding
  habitats.
• Nesting Sites- Ground squirrels that select
  optimum nesting habitats can have a greater
  proportion of their young survive.

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Physiological Adaptations
A physiological adaptation is an adaptation in
which the organism changes internally (in its
cells/tissues) due to a very specific and direct
stimuli. Ex Bacteria that have developed a
resistance to antibiotics--Tuberculosis
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Physiological Adaptations

• Other Examples Include
• Camel urineit is extremely concentrated to
  reduce water loss (desert dwelling animal)
• Callouses on fingershardened skin tissue to
  lessen pain and feeling within an area of overuse
• Tanning of skinresponse to long periods of
  time in the sun

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Biological Molecules

• Proteins Sequences few changes in amino acid
  sequences share common ancestors.
• DNA Sequences Similar gene sequences show
  evolutionary ancestors.

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Points of Evidence for Evolution

• Fossil Record Past History
• Anatomical Studies similar body parts
• Homologous structures - Modified structures seen
  among different groups of descendents. Have a
  common ancestor.
• Whale fin and human arm (similar bone structure,
  different function)
• Analogous structure - Body part similar in
  function but different in structure. Do NOT have
  a common ancestor.
• Butterfly wing and bird wing (function is the
  same, but structure is different)

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Homologous Structures
Yes Common Ancestor
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Analogous Structures
NO Common Ancestor
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Vestigial Organs

• 3. Vestigial Organs - Structures that have no
  function in the organism today but may have been
  used at an earlier time in life.
• Examples in humans Appendix, tailbone, wisdom
  teeth
• http//www.livescience.com/animals/top10_vestigial
  _organs-1.html

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Embryological Development

• 4. Embryological development - Organisms that
  develop similarly as embryos have an evolutionary
  relationship.
• Example vertebrate embryos-have tails and gill
  slits

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EmbryologicalDevelopment
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Mechanisms of Evolution or Natural Selection

• Reproductive Isolation- Occurs when a population
  is separated by geographic , mating, or
  reproductive changes.
• Can no longer breed successfully.

Grand Canyon Squirrels Geographic Isolation
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Speciation

• The formation of a new species from an ancestor.
• Occurs if inter-breeding or the production of
  fertile offspring is prevented from forming
  subspecies.

Divergent Evolution - An ancestral species
evolves into many different species (Adaptive
Radiation) Ex. Vertebrate limbs Convergent
Evolution -Distantly related organisms evolve
similar traits. Ex. whales and fish
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Speciation

• Speciation can occur quickly or slowly.
• Gradualism- Species originate through a gradual
  accumulation of adaptations.
• Punctuated Equilibrium - Occurs in rapid bursts
  with long periods of stability in between.

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Changes in Genetic Equilibrium

• Genetic equilibrium - Allele frequencies do not
  change over time (non evolving)
• 3 Ways Evolution Occurs.....
• 1) Mutations - Cause genetic changes in gene
  pool
• 2) Genetic Drift - Changes due to chance
  events (Small populations)
• 3) Gene flow - Movement of genes into or out
  of a population