Flowering_plants_-_the_angiosperms_(Anthophyta)

Flowering_plants_-_the_angiosperms_(Anthophyta) - Ioana...

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Ioana Dobre Flowering plants: the angiosperms (Anthophyta) Characterized by the evolution of: - Carpel “seed in vessel’ (= angiosperm) rather than “naked seed” *in gymnosperms, the seeds are carried on the scale of the cone, not covered in any protective structure* - True flowers with petals, sepals, anthers, pistil, etc. - Advanced word (hardwood) replaces gymnosperm wood (soft wood) *just diff structure*; hardwood is more durable than softwood - A double fertilization process occurs during reproduction this gives rise to a storage tissue called the endosperm as well as the zygote - Embryo/zygote is diploid but the endosperm is triploid (unusual feature) - One key to angiosperm success is pollination by insects Carpels: - Cut a tomato in half we see an outer ring of tissue, and then compartments with seeds i.e the concept of seeds in a vessel Early angiosperms: overview - There is a sudden an explosively abundant fossil record of angiosperms starting about 120 mybp (Cretaceous) - One early fossil record is the Koonwarra angiosperm which appeared in Australia and whose flowers resemble the pepper family - Other early flowers resembled the modern Protea or Magnolia. They had multiple, symmetrical flower parts are were possibly beetle pollinated (there were no bees around at that time) - Later simultaneous rapid expansion of flowering plants and advanced insects (hymenoptera) occurred after dinosaur extinction 65 mybp - The big break for angiosperms was the same big break that allowed mammals to become dominant - A meteor struck which lead to a global extinction - Forests of conifers were decimated and thus angiosperms which were already present were able to move in and take over During the cretaceous, the continents were combined in one supercontinent called Gondwanaland which was relatively arid. The continents began splitting up at about the same time that angiosperms evolved **We think that the place where angiosperms evolved was probably in northern Australia and also over in China Darwin’s “abominable mystery” the origin of angiosperms - Darwin’s mystery is the earliest origins of angiosperms where fossil records are very sparse *there are no fossils almost anywhere! And then they suddenly explode* - They make have evolved 200 mybp from the extinct gymnosperms called ‘seed ferns’ in upland areas ( no anoxic conditions to favor fossilization, therefore things just decompose and are recycled in the biosphere) where fossilization was poor and later invaded lowlands in Cretaceous
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Ioana Dobre - In april 2001, Dr. Sun Ge & D. Dilcher described oldest fossil flower to date - It was recently discovered near Beijing (age is 145 mybp) and clearly shows fruits
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Flowering_plants_-_the_angiosperms_(Anthophyta) - Ioana...

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