1.C.1: Speciation and Extinction

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1 1.C.1: Speciation and Extinction
JULIAN ANDERSON

2 Learning Objectives Learning Objectives:
LO 1.20 the student is able to analyze data related to questions of speciation and extinction throughout the Earth’s History See SP 5.1 LO 1.21 the student is able to design a plan for collecting data to investigate the scientific claim that speciation and extinction have occurred throughout the Earth’s history See sp4.2

3 Speciation Definition: lineage-splitting event that produces two or more separate species Speciation rates can vary, especially when adaptive radiation occurs when new habitats become available

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5 Causes of Speciation Geographic isolation Rivers change course
Mountains rise Continents drift Organisms migrate

6 Causes of Speciation Reproductive isolation
Evolution of different mating location, time, or rituals Lack of fit between sexual organs Offspring unviability or sterility

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9 Modes of Speciation Allopatric Peripatric Parapatric
Allo = other, patric = place Geographically isolated populations Peripatric Peri = near, patric = place A small population isolated at the edge of a larger population Parapatric Para = beside, patric = place A continuously distributed population

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11 Modes of Speciation Sympatric Sym = same, patric = place
Within the range of the ancestral population

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14 Extinction Definition: the cessation of existence of a species or group of taxa, reducing biodiversity Species extinction rates are rapid at times of ecological stress 5 major extinctions

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18 Causes of Extinction Competition Sudden unprecedented event
Habitat loss Fires Disease

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20 The 5 Extinctions Permian Extinction Ordovician-Silurian Extinction
266 million to 252 million years ago 95% of marine species wiped out 70% of land species Ordovician-Silurian Extinction 444 million years ago 25% of marine families 85% of marine species

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22 The 5 Extinctions Cretaceous-Tertiary (K-T)/Cretaceous-Paleogene (K-Pg) Extinction 66 million years ago 80% of all animal species End-Triassic Extinction 201 million years ago Caused by rapid climate change or asteroid striking earth 20% marine families 76% of all species

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24 The 5 Extinctions Devonian Extinctions
407 million to 359 million years ago 15-20% of marine families 70-80% of animal species

25 Further Reading life/a/species-speciation