BIOEE 1780 Lecture 30: Lecture 30
7 May 2018
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We walked on two feet (bipedal) before our brains were big.
Standing Diversity: the number of species (or other taxonomic unit) present in a particular area at a
given time
Turnover: the extinction of some species and their replacement by others (origination)
• The sum of the number of originations and the number of extinctions
Origination: the creation of a new species
Adaptive Radiation: exceptional rate of speciation; high rates of originations that occur in a relatively
short period of geologic time
• Can be rapid
• Usually occurs because organisms have a variety of "lifestyles" or niches"
• Examples
o Cambrian Explosion
o Hawaiian honeycreepers → 50 species arose over the course of 5 million years
o Hawaiian Silverswords → exhibit enormous phenotypic variation (herbs, trees, vines)
• Factors that Contribute to Adaptive Radiation
o Open habitats/niches
o Release from competition
o Evolution of a key phenotype
o High geographic habitat heterogeneity
o Sexual selection
Causes of Extinction
• Changing climate
• Loss of food resource
• Predation
• Disease
• Competition
• Loss of habitat
Diversity curve over time may be biased. It indicates there is an increase in diversity in more recent
years.
• The fossil record is biased toward younger rocks due to superposition (these fossils are closer to the
surface) - known as the Pull of the Recent.
• Environment may not have been opportune for fossilization during certain periods.
• Lagerstatten effect
• Effect of available sediments
Background Extinction: the normal (baseline) rate of extinction
• "ordinary" extinction
• The expected extinction that occurs because species are competing for resources, etc.
Mass Extinction: a statistically significant departure from background extinction rates that results in a
substantial loss of taxonomic diversity
• Occurs in multiple lineages simultaneously
Document Summary
The sum of the number of originations and the number of extinctions. We walked on two feet (bipedal) before our brains were big. Standing diversity: the number of species (or other taxonomic unit) present in a particular area at a given time. Turnover: the extinction of some species and their replacement by others (origination) Factors that contribute to adaptive radiation: open habitats/niches, release from competition, evolution of a key phenotype, high geographic habitat heterogeneity, sexual selection. Causes of extinction: changing climate, predation, disease, competition. It indicates there is an increase in diversity in more recent years. The fossil record is biased toward younger rocks due to superposition (these fossils are closer to the surface) - known as the pull of the recent. Lagerstatten effect: environment may not have been opportune for fossilization during certain periods, effect of available sediments. Background extinction: the normal (baseline) rate of extinction.
