origin of flowers and fruits - PowerPoint PPT Presentation

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origin of flowers and fruits

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  1. origin of flowers and fruits • angiosperms (seeds inside fruits • fruits develop from flowers • at least 140 my ago • coevolution w/animals--> diversification • animal pollination & seed dispersal • agriculture

  2. model organism for research Arabidopsis • small genome (sequenced) • fast lifecycle (genetics) • small size (fits in small space)

  3. flower • shoot modified for reproduction • parts are modified leaves • sepals protect • petals attract pollinators • stamens have pollen • carpels have ovules

  4. fruit • ovules inside ovary • ovary develops into fruit • fruit is mature ovary with seeds • fruit attracts seed dispersers

  5. angiosperm life cycle • further reduction in gametophyte • no antheridia OR ARCHEGONIA • sperm + egg = zygote AND • extra sperm fuses with 2 other nuclei • makes stored food: endosperm (3n) • food-->cotyledons, or not (eg corn)

  6. angiosperm seed seed coat (2n) endosperm (3n) embryo (2n) embryo is new sporophyte endosperm is stored food

  7. gymnosperms angiosperms • pollen grains • ovules • seeds (w/stored food) • food is megagphyte food is endosperm • food always made food only if fertilized • cones flowers • seeds on scale seeds in fruit

  8. types of flower • flowers solitary or in cluster = inflorescence • grasses infls. have tiny flowers, wind pollination • corn: many stigmas (silks), one /flower, each kernel is fruit • examples of inflorescences: • 1) catkin = dangling infl. (eg. oak) • tiny flowers, wind pollination • 2) composite “flower” = infl. • (eg sunflower) big, attract pollinator • each flower has own carpel (& fruit)

  9. flowers & pollinators • showy (esp red), nectar, NOT fragrant-- birds • colorless, fragrant-- beetles, nocturnal moths, bats

  10. flowers & pollinators • smell & look like dead meat-- flies • eg Titan arum—giant stinky infl. • fly pollination • male flowers (top) • female flowers • w/fly larvae • bird-dispersed fruits

  11. Thermal Images of Titan heat mimics rotting carcass, disperses smell images by Frank Landis http://www.news.wisc.edu/titanarum/facts.html

  12. co-evolution: orchids • flower shapes accomodate certain insects • Madagascar orchid, 30 cm tube • Darwin predicted pollinator • hawkmoth discovered

  13. seed dispersal • wind: orchids, dandelion, maple • animals • nutritious fruits w/changes in color, sweetness • burrs (plant velcro) coffee