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Angiosperm Evolution
Chapter 6Simpson, 2nd Edition
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 mya
Multicellar plants - 1,000 mya
Vascular tissue - 430 myaNeeded on land - why?
Seeds - 350 mya
1. Earth2. Prokaryotes3. Eukaryotes4. Multicellular life5. Vascular tissue6. Seeds7. Flowers
TimelineDevonian Period
• 400mya – 1st vasc plts• Psilotum – like
Devonian-Carboniferous• ferns, lycophytes,
sphenophytes & progymnosperms
Mesozoic• gymnosperm-dominant seed
plants
Cretaceous Period• 130 mya 1st fossil flowers• 90 mya - worldwide
angiosperm dominance
Relationships of Angiosperms
Bennettitales and Genetophytes – 225 mya
Relationships of Angiosperms
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)
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
Angiosperm Systematics
What conclusions can be drawn from this cladogram?
Angiosperm Apomorphies1. flower, usually with
perianth
Angiosperm Apomorphies2. stamens with 2
lateral thecae, each composed of 2 microsporangia
3. reduced, 3-nucleate male gametophyte
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)
Angiosperm Apomorphies5. ovules with 2 integuments• bitegmic with micropyle at distal end
Angiosperm Apomorphies6. reduced, 8-nucleate female gametophyte
Angiosperm Apomorphies6. reduced, 8-nucleate female gametophyte:• evolution of female gametophyte
Angiosperm Apomorphies7. endosperm formation• product of double fertilization• zygote = 1 sperm + egg• endosperm = 1 sperm + polar nuclei
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
Archaefructus 130 mya northern China
reconstruction of Archaefructus sinensis fossil imprint of Archaefructus lianogensis
Origin of Angiosperms
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
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)
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
Order AsteralesAsteraceae
(=Compositae)Sunflower Family1620 genera23,600 species
p. 429Fig. 8.131
Order AsteralesAsteraceae
(=Compositae)Sunflower Family1620 genera23,600 species
p. 430Fig. 8.132
Order AsteralesAsteraceae
(=Compositae)Sunflower Family1620 genera23,600 species
p. 431Fig. 8.133
Order AsteralesAsteraceae
(=Compositae)Sunflower Family1620 genera23,600 species
p. 432Fig. 8.132