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Alternation of generations life cycle
- Two multicellular bodies
- Diploid sporophyte (2N), haploid gametophyte (N)
- Spores produced by sporophyte
- By meoisis, in structures called sporangia
- Spores germinate to create gametophyte
- Gametes produced by gametophyte
- By mitosis, in structures called gametangia
- Eggs in archeogonia, sperm in antheridia
- Fertilization occurs to produce sporophyte
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Byrophytes
- Dominated by the gametophyte generation
- Gametophyte is larger, more obvious
- Sporophyte is dependent on gametophyte
- Gametophyte photosynthesizes, shares food
- Don't have true leaves, roots, or stems
- Those organs are defined by vascular tissue
- Have simpler structures ex. rhizoids
- Example: Mosses
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Moss Life Cycle
- 1) Gametophyte gametes lead to sporophyte
- Sporophyte remains attatched to gametophyte
- Attatchment is called the foot
- 2) Sporophyte capsule releases spores
- Capsule elevated by seta (stalk)
- 3) Spores produce gametophyte
- Initial spore germination creates protonema
- Protonema becomes mature gametophyte
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Pteridophytes
- Vascular plants
- Have xylem and phoem conductive tissue
- Life history dominated by the sporophyte
- Sporophyte initally dependent on small gametophyte
- Sporophyte develops to become large and self-sufficient
- Example: Ferns
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Fern Life Cycle
- Sporophyte produces sporangia
- Spores are released
- Sporophyte has leaves (fronds), stem (rhizome), & roots
- Spores germinate to produce gametophyte
- Small and sometimes heart-shaped
- Gametophyte produces gametes
- After fertilization, sporophyte develops
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