Angiosperm Evolution
Chapter 6
Simpson, 2nd Edition
Major Evolutionary Advances
Life - 3,800 mya
Prokaryotic cell/autotrophic
Eukaryotic cell - 1,400 mya
Multicellar plants - 1,000 mya
Vascular tissue - 430 mya
Needed on land - why?
1. Earth
2. Prokaryotes
3. Eukaryotes
4. Multicellular life
5. Vascular tissue
6. Seeds
7. Flowers
Seeds - 350 mya
Flowers – 130 mya
Earth
Forms
5,000
mya
Prokaryotic
Cells
4,000
mya
Eukaryotic
Cells
3,000
mya
2,000
mya
Multicellular
Plants
1,000
mya
Vascular
tissue
Seeds
Flowers
Timeline
Devonian 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 Apomorphies
1. flower, usually with
perianth
Angiosperm Apomorphies
2. stamens with 2 lateral
thecae, each
composed of 2
microsporangia
3. reduced, 3-nucleate
male gametophyte
Angiosperm Apomorphies
4. 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 Apomorphies
5. ovules with 2 integuments
• bitegmic with micropyle at distal end
Angiosperm Apomorphies
6. reduced, 8-nucleate female gametophyte
Angiosperm Apomorphies
6. reduced, 8-nucleate female gametophyte:
• evolution of female gametophyte
Angiosperm Apomorphies
7. endosperm formation
• product of double fertilization
• zygote = 1 sperm + egg
• endosperm = 1 sperm + polar nuclei
Angiosperm Apomorphies
8. 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
Origin of Angiosperms
Archaefructus 130 mya northern China
reconstruction of Archaefructus sinensis
fossil imprint of Archaefructus lianogensis
Four evolutionary trends
among flowers
1. floral parts many -> few
2. floral whorls from 4, long floral axis,
separate parts -> reduced whorls, short
floral axis, fused parts
3. superior -> inferior ovary
4. symmetry radial -> bilateral
Lonicera (honeysuckle)
Vanilla (vanilla bean orchid)
Nelumbo (Lotus)
1.
2.
3.
4.
floral parts few
reduced whorls,
short floral axis,
fused parts
inferior ovary
bilateral symmetry
Helianthus
disk floret
Anemone
Order Asterales
Asteraceae (=Compositae)
Sunflower Family
1620 genera
23,600 species
1)
2)
3)
4)
most diverse dicot family
98% herbaceous, but
shrubs, trees or vines also
inflorescence a head,
subtended by involucre of
phyllaries
K 0-∞ C (5) [4] or (3)
A (5) [(4)] G (2) inferior
p. 429
Fig. 8.131
Order Asterales
Asteraceae (=Compositae)
Sunflower Family
1620 genera
23,600 species
p. 430
Fig. 8.132
Order Asterales
Asteraceae (=Compositae)
Sunflower Family
1620 genera
23,600 species
p. 431
Fig. 8.133
Order Asterales
Asteraceae (=Compositae)
Sunflower Family
1620 genera
23,600 species
p. 432
Fig. 8.132
Order Asterales
Asteraceae (=Compositae)
Sunflower Family
1620 genera
23,600 species
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