Flowers• Reproductive structures of

angiosperms• Sepals are the outermost layer

which encloses a bud and protects the developing flower

• Petals are just inside sepals, fragrance and color attracts pollinators

• The receptacle is where sepals, petals, and sex organs attach

Flowers (cont.)• Stamen - male sex organ

– Anthers produce pollen– Filaments hold the anther up for

pollinators or wind• Pistil (aka carpel) – female sex

organ– The stigma is the sticky end where

pollen lands– The style is the “neck” which

connects the stigma to the ovary– The ovary contains ovules, when

mature the ovary becomes a fruit (ovules become seeds)

Flower Anatomy

FilamentSta

men

Anther

Pistil

Style

Stigma

Petal

Ovary

Ovule

Receptacle

Sepal

Pollination• Pollen transfers from anther to

stigma– Self-pollination – pollen fertilizes

ovule of the same plant– Cross-pollination – pollen fertilizes

ovules of another plant • thus increasing genetic variation

Cross Pollination Methods• Wind Pollination

– Inefficient, high pollen production – Flowers (if present) are small and

not colorful

Cross Pollination Methods

• Vector pollination uses animals • More efficient • Plants attract pollinators by:

– Color– Fragrance– Nectar

Coevolution• Two species evolve in response

to changes in one another

Bee Pollination

Butterfly Pollination

Bat Pollination

Moth Pollination

Seed Dispersal• Wind scatters seeds

– Maple trees, dandelions

Barbs stick to animal fur– Burdock plant

Animals eat and excrete seeds

Fertilization

1. Pollen lands on stigma

2. Pollen tube grows in the style

3. Sperm and egg form a zygote

Double Fertilization

• 2 sperm enter the ovary• 1st sperm fertilizes the egg;

results in a zygote (2N)• 2nd sperm fertilizes the

polar nuclei; forms endosperm (3N)

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