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Review Multicellular green algae (Chara) gave
rise to first land plants 475 mya Bryophytes (mosses) – lack vascular
tissues and roots, no seeds, gametophyte dominant
Pterophytes (ferns) – have vascular tissues and roots, no seeds, sporophyte dominant, swimming sperm
Seeds vs. Spores
Spores No protection or
support for embryo Rely on
environmental conditions for dispersal
Short lifetime (no dormancy)
Seeds Provide protection and
support for embryo Dispersal via various
means (fruits animals)
Dormancy allows a waiting period for ideal conditions
Five Derived Traits of Seed Plants
Reducedgametophytes
Heterospory
Ovules
Pollen
Seeds
Microscopic male andfemale gametophytes(n) are nourished andprotected by thesporophyte (2n)
Microspore (gives rise toa male gametophyte)
Megaspore (gives rise toa female gametophyte)
Ovule(gymnosperm)
Integument (2n)
Megaspore (n)
Megasporangium(2n)
Pollen grains make waterunnecessary for fertilization
Seeds: survivebetter thanunprotectedspores, can betransportedlong distances
Seed coat
Food supply
Embryo
Femalegametophyte
Malegametophyte
GymnospermsEx: Cycads, Ginkos, Gnetos,
ConifersSEED!
Inside a seed is the female gametophyte
Pollen is male gametophyte If sperm reaches ova, zygote
formsSeeds help plants survive
harsh conditionsGymnosperms have a
naked seed (cones)
Angiosperms Ex: Very diverse plants (monocots,
dicots) Flower – helps plants reproduce Fruit – helps seed dispersal
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