Processes Affecting Biodiversity.pptx

7/29/2019 Processes Affecting Biodiversity.pptx

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EXTINCTION

Is the end of an organism or of a

group of organisms . In most cases,extinction is a means by which a new speciesarises.


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1. Background

2. Mass


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also known as natural extinction

refers to the extinction that occurs naturally inthe evolution process. 0.00003% of species

become extinct naturally according to fossilrecords.

has been occurring since the origin of life onearth.


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During the ecological process, the naturalextinction occurs following the evolution of thespecies.

If a species cannot succeed in adapting to itssurroundings it eventually becomes extinct.


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gradual changes in temperature, humidity,predator -prey relationships , and tectonic platemovements.

David Raup estimates that the average speciesstays around for 4 -22million years before itbecomes extinct and that 99.9 of all the speciesthat have ever existed are now extinct.


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Ordovician (440mya)--50% of animal families

Devonian (360mya)--30% of animal families

Permian (250mya)--50% of animal families,

including 95% of marine species

Triassic (210mya)--35% of animal families

Cretaceous (65mya)--60% of animal species


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Maiasaura- "Good Mother Lizardlivedduring the late Cretaceous period, about 80 to65 million years ago, toward the end ofthe Mezoic, the Age of Reptiles.

STYRACOSAURUS- "Spiked lizardlived inthe late Cretaceous period, about 77-70 millionyears ago.

Protoceratops- "First Horned Face"lived in the late Cretaceous period, about 86 to71 million years ago, toward the end ofthe Mezoic, the Age of Reptiles.


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Is a relatively sudden, global decrease in thediversity of life forms.

Mass extinctions have occurred periodically

throughout the existence of life on Earth.


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Extinctions occur all over the world.

A large number of species go extinct.

Many types of species go extinct.

The extinctions are clustered in a short amountof geological time (a few million years is veryshort in terms of geological time).


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Five Mass Extinctions 1. End Ordovician (~445 Ma); ~12% of families, ~

65% species 2. Late Devonian (~365 Ma); ~ 14% of families, ~

72% species 3. End Permian (~250 Ma); ~ 52 % families, >90%

species

4. End Triassic (~210 Ma); ~ 12% families, ~ 65%species 5. End Cretaceous (65 Ma); ~11% families, ~ 62%

species


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PLESIOSAURS-"Near-lizards lived duringthe Mezoic Era, from the early Jurassic to theend of the Cretaceous.

AMMONITES -appeared during the Devonianand went extinct during the K-T Extinction, 65million years ago.

TRILOBITES - disappeared at the end ofthe Permian about 250 million years ago.


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1. Species Richness

2. Species Evenness


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the number of species within a particularsample area.


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trees found in an inventory plot

birds observed from a monitoring point,

beetles collected in a pitfall trap


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this refers to the evenness in number ofindividuals of each species in the area


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If there are 40 foxes, and 1000 dogs, thecommunity is not very even. But if there are 40foxes and 42 dogs, the community is quite

even.


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40 FOXES: 1000 DOGS

= NOT EVEN

40 FOXES: 42 DOGS

= QUITE EVEN

Documents

Processes Affecting Biodiversity.pptx