Biodiversity Last time Species Concept Biodiversity Measuring Biodiversity
Biodiversity Today Last time Endemism Species Concept Rates of species formation Biodiversity Mass Extinctions Measuring Biodiversity Species Area Relationship
Endemism Endemics – Species found in a particular region but no where else. Endemism – proportion of species in an area that are endemic.
Endemism
Rates of Species formation 3 major rapid origins of species diversification • Cambrian (500mya) • Paleozoic (440mya) • Triassic (250mya)
High rates of speciation • Mass extinctions – after permian extinction it took 50 million years to regain same # of families. • Increasing separation of land masses across earth. • Evolution of new life forms and types of species interaction.
Number of Species
Rates of Extinction • Background extinction rate • Mass extinction
Rates of Extinction • Background extinction rate • Mass extinction 1. Cambrian 50% of animal species 2. Devonian 75% of species 3. Permian 95% of marine and terrestrial organisms (trilobites) 4. Triassic 80% of reptiles and 65% of all species 5. Cretaceous Dinosaurs and other large reptiles
Rates of Extinction • Background extinction rate • Mass extinction 1. Cambrian 50% of animal species 2. Devonian 75% of species 3. Permian 95% of marine and terrestrial organisms (trilobites) 4. Triassic 80% of reptiles and 65% of all species 5. Cretaceous Dinosaurs and other large reptiles Species richness not directly affected by mass extinction
Rates of Extinction Current • extinction rate 100 to 1000 times of past geologic periods • Extinction for birds and mammals 1species per decade (1600 - 1700); One species per year (1850 - 1950). •Does not take into account T&E species •99% of modern extinction can be attributed to human activities. •Islands have higher extinction rates; � of extinctions occur on Islands (1600 - present).
Carolina Parakeet extinct around 1935? (1918?)
Panthera leo barbaricus Barbary Lion Extinct 1922
Tasmanian Tiger Extinct 1936
Gastric brooding frog • Extinct ? • Not found since 1985
Aldabra tortoise Seychelle saddleback Seychelle tortoise http://members.aol.com/jstgerlach/tortoise.htm
Species-Area relationship c is a taxon specific constant z is the extinction coefficient is in the range 0.1 to 0.3 Number of species S Area A
Species-Area relationship c is a taxon specific constant z is estimated using the slope log(Number of species S) log(Area A)
Mac Arthur and Wilson (1967): the theory of island biogeography
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