Table 25'1b The Geological Time Scale: Paleozoic and Precambrian

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Table 25.1b The Geological Time Scale Paleozoic
and Precambrian


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Table 25.1a The Geological Time Scale Cenozoic
and Mesozoic
Holocene



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Floras Faunas Vegetation Flora Fauna
Biota - Historical Biogeography Vegetation -
growth forms - Ecological Biogeography

• Brief History
• 200 years ago, only 1 of species
• known today had been described
• Alexander von Humboldt (early 1800's)
• First to conceptualize primary role of
• climate in determining vegetation
• Alexandre Brongniart (1800's)
• French paleobotanist
• Carried theme of climate
• vegetation to fossils
• Fossil plants indicators of past climates
• e.g., Fern/Lycopod forests in Carboniferous
• e.g., Gymnosperm forests in Mesozoic Era
• Joseph Dalton Hooker (1800's)
• Botanical evidence suggested
• that floras of disparate land

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Figure 25.3  Earths crustal plates and plate
tectonics
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Figure 25.4  The history of continental drift
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Examples of Laurasian Taxa
Oaks
Pines

• Taxa endemic to northern hemisphere

Examples of Gondwanan Taxa
Marsupials
Proteaceae

• Taxa endemic to southern hemisphere

• What is a reasonable biogeographic explanation
• for this pattern on endemism?

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Gondwanan Disjunctions - Ratite Biogeography as
an example
Cassowary
Elephant Bird
Moa
Ostrich
Rhea
Emu
Kiwi
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A Few Biogeographic Patterns

• Parallel Evolution
• succulent plants
• similar environment in
• different regions
• porcupines
• similar life
• styles evolve
• in different
• regions

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• Large-scale Biotic Depletions
• Antarctica - once heavily vegetated, now
  very few land organisms
• Subsaharan Africa - not nearly as diverse as
  tropical America, Asia
• Saharan Africa - once forested, now desert
• Continents have moved or modified
• Merging Continents - Merging Biotas
• Beringia - 60 mya - 8,000 ya
• land bridge connecting Siberia and Alaska
• examples crotalids (pit-vipers) seals sea
  lions any others?
• Isthmus of Panama - 4-6 mya
• land bridge connecting North and South America
• these continents had been isolated since Pangaea
  broke up
• NA to SA - bears otters rabbits cameloids
  (llamas et al.)
• SA to NA - armadillos porcupines opossums
• Merging Continents - Fragmenting Biotas
• Isthmus of Panama - 4-6 mya - marine faunas

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Local Scale Biogeographic Events occur all the
time e.g., fragmentation of lakes, creation
of barriers, change in river courses

• Vegetational Diversification Evolution leading
  to present conditions
• from Eocene on, Cooling, Drying trend
• - especially in non-equatorial areas
• Seasonality evolves - species had to adapt,
  move, or go extinct
• - temperatures fluctuate over a years time
• - moisture availability fluctuates over a years
  time
• Orogeny - mountain building (via subduction)
• - new habitats created at high elevations
• - runoff creates wetland habitats
• - rainshadows create deserts
• creating numerous opportunities for
  colonization/radiation