Evolution of Populations

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Evolution of Populations

• Chapter 16 (M)

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• Evolution ? a continuing process of change in a
  population of organisms over long periods of time

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History

• 1700s? Scientists believed that Species are
  Fixed and do not change
• Mid 1700s? fossil records lead Georges Buffon to
  say
• Earth is older than 6000years
• Different species arose from variation from a
  common ancestor
• 1800s? Lamarck explained fossil records species
  diversity

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Lamarck

• Proposed the theory of Inheritance of Acquired
  Characteristics? body changes developed during
  an organisms life time could be passed on to the
  offspring

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Short neck? ate up grass? had to stretch neckto
reach trees

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Lamarck

• Acquired characteristics would have to modify DNA
  to be inherited? no evidence of this
• Lamarcks theory was rejected
• Set the stage for Darwin

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• Variation in the population? long short necks
• Long necked survived? reproduced? population was
  gradually changed to long necked animals

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Darwin(1809-1882)

• Started his voyages at the age of 22 on the HMS
  Beagle
• Was responsible for collecting specimens of
  fossils
• He was aware of geological formations of land
  masses? could explain fossils of snails from
  mountains
• Studied his collections for the next 22 years

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Darwins Key Observations

1. Fossils fossil records show that organisms ?
   simpler ? complex
2. Overproduction of offspring
3. Limited supply of resources in an environment
4. Survival in a limited environment depends in part
   on features inherited from parents

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Information that influenced Darwin

• Charles Lyell? geologist proposed that the Earth
  was very old and had slowly been changing for
  millions of years
• Thomas Malthus ? economist ? social problems as a
  result of the exponential growth of the human
  population
• Artificial selection by breeders

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Darwin Concluded

1. Descent with Modification
2. Natural Selection

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Descent with Modification

• All present day organisms are related through
  descent from unknown ancestors in the past.
• These descendants of earliest organisms spread
  into different habitats? adapted to diverse ways
  of life

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Natural Selection

• Individuals whose inherited characteristics adapt
  them best to their environment are most likely to
  survive and reproduce
• Basic Mechanism of Evolution? Natural Selection

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Natural Selection

• Occurs over a vast period of time
• Individuals undergo selection, but do not evolve?
  Populations Evolve

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Evidence of Evolution

• Section 16.4(M)

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Evidence

1. Fossil Records
2. Comparative Anatomy
3. Embryonic Structures
4. DNA Homology

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Fossils

• Remains, traces or imprints of an organism
  preserved in the earths crust
• Imprint
• Mold
• Cast
• Petrified

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Fossil Records

1. Fossils the order in which they appear in
   layers of rocks
2. Fossil records show that animals plants have
   appeared in a historical sequence, fossils found
   in rocks of different ages differ because life on
   Earth has changed through time

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Each Layer represents a particular time period
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Comparative Anatomy

• The comparison of body structures in different
  species
• Homologous Structures
• Analogous Structures
• Vestigial Structures
• Ex common descent? evident in anatomical
  similarities between species in the same
  taxonomic group

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Homologous Structures

• Structures that are similar have been derived
  from a common ancestor, but have been adapted to
  different functions.
• ex humans, cats, whales, bats? all mammals
• Whales flipper does not have the same function
  as a bats wing

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Homologous Structures
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Analogous Structures

• Body parts similar in function but have different
  structures
• Ex wings of insects and birds

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Vestigial Structures

• Body parts reduced in size appear to serve no
  function

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Embryonic Structures

• Embryos of closely related organisms often have
  similar stages in development

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DNA Homology

• Comparison of genes and proteins shows the
  relationships between species

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Darwins Natural Selection A Mechanism of
Evolution
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Natural Selection

• Regional and timely
• Adapts organisms to their local environment
• Environmental factors vary from place to place
  time to time? adaptation in one situation may be
  useless in another
• Example Biston betularia? peppered moth

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Peppered Moth

• England ? two varieties? dark light
• 1850? almost all were light? industrial
  revolution? pollution? tree trunks turned black?
  light moths became easy prey
• Dark survived reproduced
• End of century ? almost all were dark

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Biston betularia peppered moth
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Populations

• A group of individuals of the same species living
  in the same place at the same time
• Mainland animal species colonizes a chain of
  distant and isolated islands? separate
  population.
• These populations adapt to their local
  environments.
• Over time, the isolated populations would become
  more and more different.
• And over many generations, the populations could
  become different enough to be separate species.

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Darwins Finches? adapted to different food
sources ?beak Structures
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Variation

• Differences among members of the same Species

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Adaptation

• Inherited trait that Improves the Chances Of
  Survival Reproduction
• Structural? mimicry? organism copies the
  appearance of another species
• Physiological? changes in the organisms metabolic
  process? penicillin? drug resistant bacteria
• Behavioral? inherited behavior pattern that
  allows organism to survive

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Adaptation- Mimicry

• Monarch? tastes bitter? birds avoid them because
  they get sick

• Viceroy(extra black lines on wings)? not bitter,
  look act like Monarchs ?birds avoid them

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Adaptation Camouflage

• Protective adaptation that allows an organism to
  blend into its surroundings
• The better the camouflage, the more likely it is
  for the organism to survive and reproduce

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Adaptation Camouflage
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Artificial Selection

• Selective breeding of domesticated plants and
  animals to produce offspring with genetic traits
  that humans value.

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From Wild Mustard to our Table
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Pesticides- Natural Selection in Action

• Spraying crops ?kill insect pests? favored the
  reproduction of insects with inherited resistance
  to the poisons