BIOL120 Lecture Notes - Lecture 5: Gymnosperm, Mesozoic, Laurasia
7 Jul 2016
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Document Summary
Successfully adapted to many different types of environments by accumulating through random mutation adn natural selection, allaes that increase likelihood of survial. Improved conducting system and many species are deciduous. Angiosperms did not appear until 130-145 mya, but spread wuickly due to selective advantages. Pollen tubes allow fertilization without fresh water needed by flagellated sperm. Seeds enclosed by ovary, at the base of a carpel, bearing a fruit (mature ovary) Both seed coat and surrounding tissues of fruit protect developing embryo. Vessel elements and deciduous leaves for efficient use of water. Deciduous habit provides wa of surviving dry or cool seasons. Improved hydraulic capacity pushed carbon-fixing capcity to new heights. Fruits aid in seed dispersal by attracting animals (co-evolution) In vascular plants, most spore-producint structures have sporophylls. Gymnosperms: sporangia developed within sporophylls and modiied branches that evolved as scales, organized into cones. Angiosperms: sporophylls containing microsporangia developed into stamen, sporophylls with megasporangium evolved into carpels.
