Adaptive Radiations

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Topic 12

• Adaptive Radiations Development

Hawaiian honeycreepers
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Adaptive Radiation

• Rapid increase in number of species

Causes?
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1. New Adaptive Zone
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Cichlid Diversity in E. Africa
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Key Innovation pharyngeal jaw apparatus system
of muscle and bone
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b. Fall of major taxa --gt rise of another

• Mammals minor group for 150 my
• - Dinosaur extinction --gt radiation

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2. Global Environmental Change

• Drying trends --gt rise of angiosperms

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3. Archipeligos
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Galapagos Finches
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Hawaiian Honeycreepers
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1. Structure may change function
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2. Structure may become elaborated

• Greater dissection of lungs
• Amphibians --gt reptiles --gt mammals

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3. Structure may become reduced
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Role of Development
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(a) Early in development
FISH LIMB BUD
MOUSE LIMB BUD
(b) Later in development
Tail
Head
Tail
Head
(c) Hypothesis
Foot
Fin
Hoxd-11 expression along long axis of limb
Hoxd-11 expression as in fish,followed by
expression toward head
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Homeotic Mutations
Structure grows in place of another
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How do Finch beaks evolve?
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its all in the timing

• robust, thick bills?
• strong, early expression of BMP4 gene (bone
  morphogenetic protein 4)
• long, probing bills?
• early expression of calmodulin gene

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Evolutionary Experiments