Biodiversity Last time Species Concept Biodiversity Measuring - - PowerPoint PPT Presentation

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Mar 04, 2023 110 likes •347 views

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

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Biodiversity

Last time Species Concept Biodiversity Measuring Biodiversity

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Biodiversity

Last time Species Concept Biodiversity Measuring Biodiversity Today Endemism Rates of species formation Mass Extinctions Species Area Relationship

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Endemism

Endemics – Species found in a particular region but no where else. Endemism – proportion of species in an area that are endemic.

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Endemism

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Rates of Species formation

3 major rapid origins of species diversification

Cambrian (500mya)
Paleozoic (440mya)
Triassic (250mya)

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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.

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Number of Species

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Rates of Extinction

Background extinction rate
Mass extinction

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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

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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

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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
ccur on Islands (1600 - present).

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Carolina Parakeet

extinct around 1935? (1918?)

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Panthera leo barbaricus Barbary Lion

Extinct 1922

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Tasmanian Tiger

Extinct 1936

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Gastric brooding frog

Extinct ?
Not found since

1985

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Aldabra tortoise Seychelle saddleback Seychelle tortoise

http://members.aol.com/jstgerlach/tortoise.htm

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Species-Area relationship

Number

f species S

Area A

c is a taxon specific constant z is the extinction coefficient is in the range 0.1 to 0.3

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Species-Area relationship

log(Number

f species S)

log(Area A)

c is a taxon specific constant z is estimated using the slope

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Mac Arthur and Wilson (1967): the theory of island biogeography

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