Polyploidy results from nondisjunction of chromosomes during meiosis

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Polyploidy results from non-disjunction of
chromosomes during meiosis

• 1) Autopolyploidy

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• 2) Allopolyploidy
• Hybridization followed by non-disjunction

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Polyploids are phenotypically different
reproductively isolated from parents

• Instant speciation

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• Wheat evolved by allopolyploidy

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Polyploidy is rare in animals
An all-female species
New Mexican whiptail
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How many species are there?

• 1.5 - 2 million named species
• 42,000 vertebrates
• 13 - 14 million total (?)
• (mostly insects microorganisms in tropics)
• gt 99 of all species have gone extinct

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How is evolutionary history reconstructed?
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How is evolutionary history reconstructed?

• 1. Comparison of living species

Homologies indicate common ancestry
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Time ?
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Molecular comparisons
Frog
Monkey
Chimp
Whale
A Molecular Clock
Time ?
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How is evolutionary history reconstructed?

• 2. Fossil Record

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Four Geological Eras
Cenozoic
Mesozoic
Paleozoic
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Four Geological Eras

• 1. Precambrian (4.6 0.6 b.y.a.)
• initially no atmospheric O2
• organic molecules accumulated
• (primordial soup)

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Origin of Life
3.5 b.y.a. - First Fossils
3.9 b.y.a. - Origin of Life?
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Evolutionary Innovations of The Precambrian

• Photosynthesis, and then aerobic respiration
• Eukaryotic cell
• - endosymbiosis
• Multicellularity ?
• 1 b.y.a

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(No Transcript)
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• 2. Paleozoic (543 245 m.y.a.)

Paleozoic
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• 2. Paleozoic (543 245 m.y.a.)
• Begins with "Cambrian Explosion"
• - all remaining invertebrate phyla evolve in
  40-50 million years

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Evolutionary Innovations of The Paleozoic

• gut with two openings

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Evolutionary Innovations of The Paleozoic

• gut with two openings
• complex nervous system (cephalization)

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Evolutionary Innovations of The Paleozoic

• gut with two openings
• complex nervous system (cephalization)
• shells exoskeletons

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Three Vertebrate Classes evolved during the
Paleozoic

• Fish 500 mya

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Three Vertebrate Classes evolved during the
Paleozoic

• Reptiles 250 mya
• Amphibians 400 mya
• Fish 500 mya

Modification of pre-existing structures
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Paleozoic ended with a major Extinction

• gt 90 of all species disappear

Pangea forms
Sea level drops
Volcanic activity
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• 3. Mesozoic (245 - 65 m.y.a.)

Mesozoic
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• 3. Mesozoic (245 - 65 m.y.a.)
• "Age of Reptiles"

Birds Mammals appear early but dinosaurs are
ecologically dominant
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Evolutionary innovations of the Mesozoic

• flowering plants

Cycad
Magnolia
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• homeothermy

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• vertebrate flight

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Mesozoic ends with major Extinction

• 50 of all species disappear

Asteroid Impact
Volcanic Activity
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• 4. Cenozoic (65 m.y.a. - today)

Cenozoic
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• 4. Cenozoic (65 m.y.a. - today)
• "Age of Mammals"

diversified to fill empty niches
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History of life is marked by

• Innovation leading to adaptive radiation
• Extinction leading to adaptive radiation

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Species adapt to fill ecological niches
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