Continental Drift

1
Continental Drift Speciation
2
Continental Drift

• Alfred Wegener
• In the 1930s suggested that continents were (and
  are currently) moving relative to each other and
  that at some time in the past they were joined
  together forming a super continent Pangea

3
Continental Geography

• The eastern coast of South America and the
  western coast of Africa appear to fit nicely
  together like pieces of a puzzle

4
Paleontology Climate

• The ranges of fossil plant and animal specimens
  of similar age appear to correlate well across
  current continental boundaries
• Tropical fossils exist in Antarctic sediment
  suggesting that this continent has not always
  existed in its current location

5
Past Glacial Events

• Mapping of the extent of glacial rock remains on
  the different continent suggests particular
  connections between the continents in the past

6
Plate Tectonics

• Continental Drift was not taken seriously by the
  geological community until a mechanism that could
  explain the movement of the continents could be
  developed

7
Ruggedness of the Ocean Floor

• Through development of sonar and more extensive
  use of submarines a picture of a rugged sea floor
  emerged (previously it was thought that the ocean
  floor was flat)
• In fact, the Earths largest feature is the
  Mid-Atlantic Ridge running down the middle of the
  Atlantic Ocean

8
Oceanic Ridges

• At ocean ridges new crust arises from magma
  within the Earth forcing the existing plate out
  while a new border for the plate is being made

9
Magnetic Striping

• As new magma cools magnetic crystals within it
  line up with the magnetic poles of the Earth
• The north end facing north and the south end
  facing south

10

• As magma in the Earths core circulates magnetic
  or polar reversals occur
• Our current north and south flip such that the
  magnetic crystal line up opposite of what they
  would be normally.

11
Oceanic Trenches

• Where two plates come together one is subducted
  under the other forming a trench
• Tension builds up in the plate laying on top
  while heat may generate magma below (Mts
  Volcanoes)

12

• Mapping of the distribution of Earthquakes across
  the globe correlates well with places were plates
  are coming together

13

• http//pubs.usgs.gov/publications/text/
• Information on Continental Drift and Plate
  Tectonics

14
(No Transcript)
15
Speciation

• Process by which
• a) subpopulations of one species diverge
  becoming adapted to different environments and
  reproductively isolated
• b) descendants of a species become adapted to
  an environment different than the one in which
  it was originally adapted

16
Allopatric Speciation

• Type of speciation in which the subpopulations
  diverge because they are separated by a
  geographic barrier

17
(No Transcript)
18
Reproductive Isolation

• Pre-Zygotic Mechanisms
• 1) Temporal
• 2) Behavioral
• 3) Mechanical
• 4) Ecological
• 5) Gametic Mortality

• Post-Zygotic Mechanisms
• 1) Hybrid Inviability
• 2) Hybrid Sterility
• 3) Low Fitness Hybrids