ANGIOSPERMS DIVERSITY

 The Gnetophytes is a monophyletic group  Similarities between Gnetophytes & Angiosperms is convergent evolution Phylogeny of Angiosperms Basal angiosperms

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