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Transcript
SEEDS AND POLLEN ARE
REPRODUCTIVE
ADAPTATIONS
• SEEDS ARE AN IMPORTANT
ADAPTATION
• SOME PLANTS REPRODUCE WITH
SEEDS
• PINE TREES REPRODUCE WITH
POLLEN AND SEEDS
• GYMNOSPERMS ARE SEED PLANTS
Seeds Are An Important Adaptation
• Seed= young plant enclosed in
protective coating; enough nutrients
within to grow.
• Seeds & spores both can withstand
harsh conditions but seeds have
advantages.
• In seed plants, fertilization brings
growth of an embryo within seed (not
just another plant growing like with
spores); seed coat protects plant
embryo until good conditions(temp. &
moisture), then seed starts to grow.
• Germination= beginning of new plant
from spore or seed. Seed will take in
water and as embryo grows, uses
stored nutrients for energy & materials
(till roots & shoots start working).
Some Plants Reproduce with
Seeds and some with Spores
SEEDS
SEEDS &
SPORES
SPORES
Multicellular
embryo inside
Protective
coating
Made of single
cell
Has supply of
nutrients inside
Can survive dry, Has no supply
harsh conditions of nutrients
Spread by wind, Has parent
Mostly spread
animal or water plants’ same
by wind
genetic material
Pine Trees Reproduce with Pollen
and Seeds
• Seed plants like pine tree don’t
have swimming sperm but pollen
instead;
• Pollen grain= small, mulitcellular
structure holding sperm cell in hard
outer covering; can be carried by
wind, water or animals
• Pollination process completed
when pollen grain attaches to part
of plant holding egg & sperm is
released.
• Pine tree life cycle is good example
of how seed plants reproduce.
•
•
•
•
•
PINE
TREE
LIFE
CYCLE
Reproductive structure= pinecone; meiosis occurs
in it making sperm & egg cells. Each tree has male
and female cones.
Male cones have sperm cells in pollen grains
released into air. Female cones have egg cells in
protective compartments within cone scales.
Female cone makes sticky substance for pollen to
stick to. Pollen tube grows into egg so fertilization
occurs (when sperm meets egg)
Fertilized egg grows into embryo, which is held in
seed (in female cone). Cone releases winged seeds
to float in wind, land, germinate, and grow into new
pine tree. (see p. 101 of text!)
Sperm in pollen grain & egg in cone scale = 1st
generation of plant; seed & tree that grows is 2nd.
Gymnosperms are Seed Plants
• Most plant species on Earth reproduce with
seeds, and many seedless plants are extinct
(maybe because Earth is thought to have become
drier & cooler- better for seeds)
• Gymnosperms make seeds, but not enclosed in
fruit (means “naked seed”).
• Conifers (cone-bearing trees) are common
gymnosperms; pine, fir, spruce, hemlock,
cypress, and redwood trees. Found in colder
climates that don’t need much water.
• Conifer leaves are needle-shaped with thick
cuticle(preventing transpiration of water); keep
needles for years, so make sugar all year long.
Other Gymnosperms
• Cycads, gnetophytes & ginkgoes are other types of
gymnosperms.
• Cycads: palm-like plants in tropics; make cones for
seeds & many make poisons
• Gnetophytes: also make cones in tropics; chemicals
from them have been used to treat cold symptoms
for thousands of years
• Ginkgoes: make fleshy seeds that hang from
branches. Often seen in parks & on streets, but
usually don’t see seeds (keep male & female trees
apart because seed coat smells bad).