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Exam 4 - Coggle Diagram
Exam 4
Steps
Evolution of the Ovule
Heterospory
Megasporangium enclosed in integuments
Retention of megaspores within megasporangium
Reduction # of megasporocytes/megasporangium to 1
Survival of 1 megaspore
Endosporic megagametophyte
Modification of megasporangium apex of microspores or microgametophytes
Embryos develop within megagametophyte
Heterospory
Megaspores
Megagametophyte
Microspores
Microgametophyte
Megasporangium Enclosed in Integuments
First integument
Telomes
Second integument
Phyllad origins
Reduce # of Megasporocytes/Megasporangium to 1
Megasporocyte
Megaspore mother cell
Reduced to one per megasporangium rather than hundreds
Survival of 1 Megaspore
Megasporocyte undergoes meiosis
4 resulting daughter cells
3 megaspores degenerates
1 megaspore remains
Retention of Megaspores within Megasporangium
Reduced megaspores w/ other 3 aborted
Large megaspores retained inside megasporangium
The extra layer of protection
Endosporic Megagametophyte
Megagametophyte retained inside Megapore wall
Fertilization of the egg occurs in the wall
An extra layer of protection
Modification of Megasporangium Apex
Pollen Chamber
Through programmed cell death
Micropyle
Embryo Develop within Megagametophyte
Multicellular megagametophyte
Egg retained
After syngamy, an embryo develops within
Seeds
Origins
Seed Plants
Seed ferns (extinct)
Gymnosperms
Progymnosperms (extinct)
Angiosperms
Primitive Ovule
Lobate integuments
Free form nucellus/megasporangium
Enclosed Ovule
Complete enclosure of megasporangium within integument
Increases protection
Ovule Evolution
Evolved from the shoot apex
Gymnosperm nucellus apex similar to shoot apex
Similar genes
Innovations
Heterospory
Protection
Integuments
Pollen capture
Pollen chamber
Micropyle
Nucellus
Microgametophytes
Pollen
