Angiosperm Evolution
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Transcript of Angiosperm Evolution
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Angiosperm Evolution
Chapter 6Simpson, 2nd Edition
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Major Evolutionary Advances
Flowers – 130 mya
5,000mya
4,000mya
3,000mya
2,000mya
1,000mya
EarthForms
ProkaryoticCells
EukaryoticCells
MulticellularPlants
Vascular
tissue
Seeds
Flowers
Life - 3,800 myaProkaryotic cell/autotrophic
Eukaryotic cell - 1,400 myaMulticellar plants - 1,000 myaVascular tissue - 430 mya
Needed on land - why?Seeds - 350 mya
1. Earth2. Prokaryotes3. Eukaryotes4. Multicellular life5. Vascular tissue6. Seeds7. Flowers
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TimelineDevonian Period
• 400mya – 1st vasc plts• Psilotum – like
Devonian-Carboniferous• ferns, lycophytes,
sphenophytes & progymnosperms
Mesozoic• gymnosperm-dominant seed
plantsCretaceous Period
• 130 mya 1st fossil flowers• 90 mya - worldwide
angiosperm dominance
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Relationships of Angiosperms
Bennettitales and Genetophytes – 225 mya
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Relationships of Angiosperms
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Systematics
• phylogeny represented by cladogram (phylogenetic tree• branching diagram that
conceptually represent the evolutionary pattern of descent
• lines represent lineages, with implied time scale
• branch = divergence• ancestral = preexisting• apomorphy = derived
(evolutionary novelty)
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Systematics• Phylogenetic Systematics
(cladistics)• methodology to infer
evolutionary history using apomorphies
• recognizes monophyletic groups (= clade)
• Phylogenetic Classification Scheme can result
• avoids:• paraphyletic groups
• com anc but not all descendants• polyphyletic groups
• two or more sep groups with sep anc
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Angiosperm Systematics
What conclusions can be drawn from this cladogram?
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Angiosperm Apomorphies1. flower, usually with
perianth
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Angiosperm Apomorphies2. stamens with 2
lateral thecae, each composed of 2 microsporangia
3. reduced, 3-nucleate male gametophyte
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Angiosperm Apomorphies4. carpels and fruit formation
• conduplicate (inwardly folded longitudinally & along the central margin) megasporophyll bearing 2 adaxial rows of ovules
• carpel body encloses seed (angiosperm name origin)
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Angiosperm Apomorphies5. ovules with 2 integuments• bitegmic with micropyle at distal end
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Angiosperm Apomorphies6. reduced, 8-nucleate female gametophyte
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Angiosperm Apomorphies6. reduced, 8-nucleate female gametophyte:• evolution of female gametophyte
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Angiosperm Apomorphies7. endosperm formation• product of double fertilization• zygote = 1 sperm + egg• endosperm = 1 sperm + polar nuclei
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Angiosperm Apomorphies8. sieve tube members• sieve plates – contain pores at end walls
larger than lateral pores• sieve cells are primitive sugar-conducting
cells
vessels found in all but primitive angiosperms
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Archaefructus 130 mya northern China
reconstruction of Archaefructus sinensis fossil imprint of Archaefructus lianogensis
Origin of Angiosperms
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Four evolutionary trends among flowers
1. floral parts many -> few2. floral whorls from 4, long floral axis,
separate parts -> reduced whorls, short floral axis, fused parts
3. superior -> inferior ovary4. symmetry radial -> bilateral
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1. floral parts few2. reduced whorls,
short floral axis, fused parts
3. inferior ovary4. bilateral
symmetry Anemone
Lonicera (honeysuckle)
Nelumbo (Lotus)
Helianthus disk floret
Vanilla (vanilla bean orchid)
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Order AsteralesAsteraceae
(=Compositae)Sunflower Family1620 genera23,600 species
1) most diverse dicot family 2) 98% herbaceous, but
shrubs, trees or vines also
3) inflorescence a head, subtended by involucre of phyllaries
4) K 0-∞ C (5) [4] or (3) A (5) [(4)] G (2) inferior
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Order AsteralesAsteraceae
(=Compositae)Sunflower Family1620 genera23,600 species
p. 429Fig. 8.131
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Order AsteralesAsteraceae
(=Compositae)Sunflower Family1620 genera23,600 species
p. 430Fig. 8.132
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Order AsteralesAsteraceae
(=Compositae)Sunflower Family1620 genera23,600 species
p. 431Fig. 8.133
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Order AsteralesAsteraceae
(=Compositae)Sunflower Family1620 genera23,600 species
p. 432Fig. 8.132