BIO2231 Lecture Notes - Lecture 23: Biogeography, Continental Drift, Reproductive Isolation
Lecture 23 –
Diversity and habits Exams
Speciation
• Allopatric
o Population separated by geographic barriers
o Interruption of gene flow
o Physical barriers
o Different selective pressures
o Divergence
o Start of with population get separated by physical barriers → isolated
▪ Reproductive isolation
• Sympatric
o Don’t have geographical barriers/isolation
o Separate for other ecological reasons
o Have isolation occurring between population of same species initially
→ ecological separation → evolved to become divergent species over
long time periods
Extinction
• 5th mass extinction event (currently experiencing 6th – climate change)
• Opens up niches for new adaptive radiations
Discontinuous
• Dispersal
• Vicariance (geographic isolation)
o Evolved to become different species
o Each
Species dispersal
• Global distribution – cosmopolitan species
o Found everywhere: rats, flies
• Water bears – not globally distributed
Global Patterns
• Continental drift
o Some distributions can be explained by the history of connections
between continents
o Marsupials in Australia
• Latitudinal cline in biodiversity
o Less diversity further away from tropics
o More diversity around tropics
▪ Tropics are stable, productive and old
• Biogeographic regions
o Map patterns of biodiversity based on biogeography of different
continents of ocean as well
o Maps based on vegetation type
• Hotspots of biodiversity
o Conservation perspective
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