4.3

• Even the most remote islands still have organisms that inhabit them. How is this possible if there is no visible connection to the mainland?
• Scientists, for centuries, have studied the patterns of distribution that organisms have.
• Scientists believe that looking at these patterns may give insights regarding how species have developed over the history of Earth.
• Biogeography


  The primary concern is knowing when and where species existed in order to determine evolutionary and ecological relationships
• The Science of Biogeography

  1. Initial dispersal of a portion of the population

  2. Dispersed population starts to diverge from original population

  3. Isolation of population due to geographic barrier

  4. The formation of mountain ranges and other landforms can cause vicariance
• Dispersal


  How plants spread seeds around and how organisms occupy different geographic locations through movement
• Vicariance


  When a barrier appears which isolates two populations of the same species that were once connected
• Phenomena That Shape Biogeographical Patterns

  • Continental Drift
  • Climate and Sea Level Change
  • Migration
  • Geographical Barriers
  • Center of Origin
• Continental Drift


  A theory proposed by Alfred Wegener suggesting that most of today's continents were once connected
• How Alfred Wegener imagined Pangea looked like

  • Shared faunal composition of the continents based on fossils
• Climate and Sea Level Change

  Changes in sea levels affected the amount of land available for organisms to thrive in, and may have affected how species were dispersed and how they interacted with each other
• Some places found below sea level

  • The Bering land bridge between Russia and North America
• Migration


  The movement of populations from one geographic location to another, which can be either emigration (movement away from an area) or immigration (movement into an area)
• Geographical Barriers


  Landforms like mountains and valleys, or bodies of water like rivers and oceans
• Center of Origin


  A geographic location where multiple species have been proven to have acquired distinct characteristics which may have led to speciation
• Evidence suggests that most of today's continents were once connected to an ancient supercontinent known as Pangaea
• The dip in sea levels meant that land bridges, which is a stretch of land that connected areas in times when sea levels were low, became exposed from underwater
• Migration refers to the movement of populations from one geographic location to another, which can be either emigration or immigration