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ANGIOSPERMS DIVERSITY
Phylogeny of Angiosperms
Basal angiosperms
The Gnetophytes is a monophyletic group
Similarities between Gnetophytes & Angiosperms is convergent
evolution
Example : Magnolias
Features:
- Many-free parts
- A single pore on pollen
- Glands that produce ether-like oil (nutmeg, pepper)
Characteristics common to almost all
Angiosperms
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Evolution of the gymnosperms into angiosperms
involved many alterations:
Conversion of the gymnosperms sporophylls into
flowers
Carpels are angiospermous (closed) - protection
Pollen must interact with the stigma – tested
Tough & resistant seeds protect embryo from
drying
Deciduous feature (resistance to drought & cold)
Characteristics common to almost all
Angiosperms
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Double fertilization (endosperm)
Reduced gametophytes
Genome duplications
Nitrogen fixation (10 families)
Synorganized flowers
chemical evolution (pollination, dispersal,
defense)
evolution of the vessel elements and sieve tubes
Vessels in Angiosperms
Vessels are shorter & wider than tracheids
Sieve cells & sieve tubes
Conifers’ Phloem
Angiosperms’ Phloem
Which of the above evolved
first?
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Double fertilization and the flower
Sieve tubes (lacking in only 1 or 2 species)
Vessels - many species lack vessels
Herbaceous habit - all herbs have vessels
Other derived features:
 Fusion of parts (sympetally)
 Reduction of parts
 Flower zygomorphic