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 Multicellular embryo inside Has supply of nutrient s inside SEEDS & SPORES Protective coating SPORES Made of single cell Can survive dry, harsh conditions Has no supply of nutrients Spread by wind, animal or water Has parent plants’ same genetic material Mostly spread by wind

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 released.

& sperm is • 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 = 1 st generation of plant; seed & tree that grows is 2 nd .

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).