08-Introduction to seed plants, Cycadophyta,...

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BIOL1309 EVOLUTIONARY DIVERSITY 7. Evolution of seed plants
VASCULAR PLANTS VASCULAR PLANTS
SEEDLESS VASCULAR PLANTS PTERIDOPHYTES or FERNS & FERN ALLIES
SEED PLANTS SEED PLANTS
MEGAGAMETOPHYTE MICROGAMETOPHYTE SPOROPHYTE sperm egg zygote megaspores microspores HETEROSPORY & ENDOSPORY EVOLUTIONARY ADVANCE OF SEED PLANTS
Two evolutionary advances associated with this: 1. POLLEN GRAIN 2. OVULE and SEED EVOLUTIONARY ADVANCE OF SEED PLANTS
POLLEN GRAINS: General characteristics Male spores ( MICRO- SPORES ) with endosporic male gametophyte ( MICROGAMETOPHYTE )
Pollen grain germinates to produce POLLEN TUBE that conveys the sperm to the egg POLLEN GRAINS: General characteristics
Pollen grain has resistant wall made of SPOROPOLLENIN POLLEN GRAINS: General characteristics
POLLEN GRAINS: Evolutionary advantages In seedless vascular plants, the sperm (antherozoid) is motile, and has to swim to reach the egg in the archegonium; water is therefore required In seed plants, the pollen grain is adapted for transporting the sperm: thick sporopollenin wall protects microgametophyte; pollen tube conveys sperm to the egg
OVULE: General characteristics The OVULE is a multi- layered structure: 1.

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