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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 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 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? 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