EVOLUTION

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EVOLUTION
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Variation

• The differences between individual members of a
  population (ex fur color, eye color, etc.)
• Can not always be observed
• Are almost always genetically inherited
• Results from mutations and recombination

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Adaptation

• An inherited trait that increases the
  populations chances of survival and reproduction
• It can be physical or behavioral

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Evolution

• Defined as change over time
• There were 3 scientists who made important
  contributions to this field
• Charles Bonnet
• Jean-Baptiste Lamarck
• Charles Darwin

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Charles Bonnet

• Noticed that fossils didnt look like modern
  organisms
• Theorized that periodic catastrophes affected the
  entire planet and after each catastrophe life
  began anew

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Jean-Baptiste Lamarck

• Challenged Bonnets views
• Believed that the fossils of extinct animals were
  the ancestors of those living today
• Developed Lamarcks hypothesis

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Lamarcks Hypothesis

1. Organisms strive to improve themselves
2. Principle of Use and Disuse the most-used body
   structures develop, whereas unused structures
   waste away
3. Principle of Inheritance of Acquired
   Characteristics modified structure is inherited
   by the organisms offspring

This 3rd principle was disproved by August
Weismann. Changes in an individual during its
lifetime do not affect its reproductive cells or
its offspring.
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Charles Darwin

• Scientist who studied plants and animals while on
  an around-the-world trip
• After studying several organisms, he developed
  his theory of evolutionNatural Selection

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Natural Selection

1. There is variation within populations
2. Some variations are favorable favorable
   variations improve an organisms ability to
   function and reproduce in its own particular
   environment
3. Not all young produced in each generation can
   survive
4. Individuals that survive and reproduce are those
   with favorable variations

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Rate of Evolution

• Gradualism
• states that evolution occurs at a slow, gradual
  rate
• this is what Darwin believed
• Punctuated Equilibrium
• states that populations remain genetically stable
  for long periods of time, interrupted by brief
  periods of rapid genetic change
• this new theory was first stated by Stephen Jay
  Gould and Niles Eldridge

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Comparing Anatomy

• Homologous Structures
• structure or characteristic with similar
  functions found in different species
• thought to be inherited from common ancestors
• EX humans, whales, and bats all have the same
  number and type of bones in the forelimbs

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Comparing Anatomy (cont.)

• Analogous Structures
• structures that are similar in function, but are
  not inherited from a common ancestor
• EX wings of insects and wings of birds

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Comparing Anatomy (cont.)

• Vestigial Structures
• structures that are inherited, but reduced in
  size and often unused
• suggest structures of the ancestors of modern
  organisms
• EX pythons have vestigial hip and leg bones

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Types of Evolution

• There are 5 different types of evolution
• Speciation
• Divergent Evolution
• Convergent Evolution
• Coevolution
• Adaptive Radiation

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Speciation
new species
species
original species
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Divergent Evolution
new species
species
new species
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Convergent Evolution
species
new species
new species
species
These two succulent plant genera, Euphorbiaand
Astrophytum, are only distantly related, but have
independently convergedon a very similar body
form.
These 2 new species share many traits.
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Coevolution
species
original species with new traits
Bumblebees and the flowers they pollinate have
coevolved so that both have become dependent on
each other for survival
original species with new traits
species
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Adaptive Radiation
new species
new species
species
new species
new species
new species
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Population Genetics

• Populations are the smallest unit in which
  evolution takes place
• Population genetics is the study of genetic
  traits and changes in populations

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Hardy-Weinberg Principle

• If a population is not evolving, the allele
  frequencies in the population remain stable
• The population is said to be in genetic
  equilibrium

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Conditions Required to Maintain Equilibrium

1. No natural selection
2. Random mating
3. No migration
4. No mutation
5. Very large population size

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Types of Selection

• In stabilizing selection, the extreme phenotypes
  are selected against

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Types of Selection (cont.)

• In directional selection, there is a shift in
  frequency to an extreme phenotype

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Types of Selection (cont.)

• In disruptive selection, the most common
  variation in a population is not favored