seed plants angiosperms and gymnosperms. gymnosperms seed plants that produce “naked seeds”....
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Seed Plants Angiosperms and Gymnosperms
Gymnosperms •Seed plants that produce “naked seeds”.
•Seeds are not enclosed by a fruit. •The oldest type of seed plant.
• Gymnosperms Many have needle-like or scale-like leaves. Pacific yew -- taxol
Four Types of gymnosperms …Cycads – Ancient plants.
Look like palm trees with cones. Grow mainly in tropical or subtropical areas.
Conifers – “cone bearing”. Largest and most diverse gymnosperm group today. Most are evergreens… like firs, pines, spruces,
sequoias, junipers.
Gnetophytes• Found in deserts and tropical rain forests.• Are trees, shrubs, or vines. Some may live for
more than 1000 years. Ephedra – ephedrine - decongestant
Gymnosperm reproduction Cones – reproductive structures Usually, both male and female cones are made by a single plant. Cones are covered by scales.
Scales on male cones produce pollen – the male gametophyte! Each scale produces thousands of pollen grains.
Scales on the female cone contain at least one ovule at the base. Ovule is female gametophyte.Ovule contains egg cell. What
advantage do these gametophytes have over those of nonvascular and seedless plants?
4 Steps of reproduction 1. Pollination – Wind often carries the pollen to the female cones. Pollen sticks
to substance produced by ovules.
2. Fertilization -- After pollination, ovule closes and seals. p.275
3. Seed Development -- Female cones stay on tree and get bigger as seeds mature. May take up to 2 years.
4. Seed Dispersal -- Scales open when seeds mature. Wind carries them away. Few will land in places suitable
for germination.