BIOL 3445 Lecture Notes - Lecture 24: Cambrian Explosion, Continental Drift, Macroevolution
BIOL 3445.001 | Lecture #24 | 4/12/2018
Macroevolution
OBJECTIVES
― Explain the difference between microevolution and macroevolution
― What processes lead to the patterns of biogeography we see today?
― Why do species become extinct?
― What are adaptive radiations and why do they occur?
― Explain the factors that might have led to the Cambrian explosion
WHAT IS MACROEVOLUTION?
― Microevolution: changes in allele frequencies within populations
o Caused by genetic drift and selection
― Macroevolution: large-scale processes and patterns of evolution
o Speciation
o Changes in levels of biological diversity
o Extinction
― Group Exercise:
o Where can you draw a line between what is microevolution and
macroevolution?
▪ Microevolutionary changes lead to macroevolutionary speciation
▪ Macro is the result of generations’ worth of micro-changes
▪ A speciation event (when two species split into 2+)
o Should we make a distinction between them?
▪ Yes, because they are not interchangeable
▪ Microevolution leads to macroevolution but not vice versa
BIOGEOGRAPHY
― Biogeography: the study of species distributions across space and time
o How can we explain the patterns we see in the types and number of
species around the world?
o Influenced by the movement of species and changes in the geography
of the Earth
o Where are species? How did they get there? Why are they there?
― Dispersal: the movement of populations from one geographic region to another
o Different organisms have very different dispersal patterns
o For example, islands tend to be colonized
by organisms that can fly, swim, or float
― Vicariance: the formation of geographic barriers
to dispersal and gene flow
o Rising mountain ranges
o Sea level changes
o Formation of islands
o Continental drift
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Document Summary
Explain the difference between microevolution and macroevolution. Explain the factors that might have led to the cambrian explosion. Microevolution: changes in allele frequencies within populations: caused by genetic drift and selection. Macroevolution: large-scale processes and patterns of evolution: speciation, changes in levels of biological diversity, extinction. Dispersal: the movement of populations from one geographic region to another: different organisms have very different dispersal patterns, for example, islands tend to be colonized by organisms that can fly, swim, or float. Vicariance: the formation of geographic barriers to dispersal and gene flow: rising mountain ranges, sea level changes, formation of islands, continental drift. The current patterns of biogeography that we can observe are due to both dispersal and vicariance: we can study these patterns by looking at molecular data, the fossil record, geology, etc. Marsupials today live in australia, south america, and one species (possum) in.
