Evolution of AngiospermsChapter 20

Archaefructus sinensis

Rafflesia arnoldii

True or False1) Flowers are the

reproductive structures of angiosperms.

2) Flowers are determinate shoots that bears sporophylls.

Evolutionary Trends Among Flowers1) Flowers have gone from many indefinite parts to having

fewer parts that are definite in number. 2) Floral whorls have reduced over time.3) Floral parts have become fused.4) Floral axes have become shortened.5) Carpels have gone from leaflike and incompletely closed

to pistil-shaped and sealed.6) Ovaries have gone from superior to inferior.7) Perianths have gone from having indistinct sepals and

petals to having a distinct calyx and corolla.8) Flowers have gone from radial (actinomorphic) to

bilateral (zygomorphic) symmetry.

• Which of the following is not involved in flower pollination?– A) bees– B) bats– C) beetles– D) toads named Mel– E) land mammals, i.e. mice– F) birds

True or False

• Floral evolution was and still is driven by animals.

Floral Evolution

• Flowers and insects have coevolved.– Coevolution- the simultaneous

evolution of adaptations in 2 or more interacting populations.

• Insect pollination is more efficient than passive pollination.

• Beetles, flies, bees.• Bees are the most important

group of visiting insects.

Bird and bat-pollinated flowers

• Produce copious nectar.

• Usually bright red and yellow in color.– Birds have a good sense

of color.

• Flowers usually have very little odor.– Smell not developed in birds.

Flavonoids• Water soluble phenolic compounds with two

six-carbon rings linked by a three-carbon unit.

• Occur in the vacuole of plant cells.

• The most important pigments in floral coloration are the anthocyanins (red, violet, and blue) and the flavonols.

Wind pollinated flowers do not produce nectar.

Asteraceae and Orchidaceae• Asteraceae

– Composites have flowers closely bunched together in a head.

• 22,000 species.• Ovary with 1 ovule• Disk and ray flowers.

• Orchidaceae– Orchid flowers are showy

and zygomorphic.• 24,000 species.• Ovary with 1,000s of ovules.• Cuplike lower petal.

Fruit Related Terminology

• Fruit- a mature ovary.• Ovary- the enlarged basal portion of a carpel.• Carpel- the vessel that encloses the ovule/s; forms

the gynoecium.• Ovule- the structure that contains the female

gametophyte with egg cell, including the nucellus and integuments.

• Seed- a mature ovule.• Locules- chambers in the ovary that contain the

ovules.

Parietal

Free central

Axile

Fruit Classification

• Fruit derived from more than 1 pistil– Multiple fruit- develop from a cluster

of mature ovaries produced by a cluster of mature flowers.

• Pineapple.

– Aggregate fruit- develop from several separate carpels of a single flower.

• Raspberry, strawberry, blackberry.

Simple Fruit Types- fruit derived from 1 pistil• Fleshy Simple Fruits

– Berries- fleshy inner layer. Tomatoes, bananas, grapes.• Pepo- a berry with a thick, leathery, inseparable rind. Cucurbitaceae.• Hesperidium- a berry with a thick, leathery, separable rind. Citrus.

– Pome- fleshy hypanthium. Pear, apple.– Drupes- stony endocarp. Peach, cherry, olive.

• Dry Simple Fruits– Dehiscent- tissue of the mature ovary wall splits open, freeing

the seeds.• Legume- dehisces along 2 sutures. Bean.

– Indehiscent- tissue of the mature ovary wall remains sealed with seeds remaining in the fruit.

• Nut- hard pericarp, usually one-seeded.• Achene- small. Dandelion.

Fruits and seeds have evolved in relation to their dispersal agents

• Wind-borne fruits & seeds.

• Floating.

• Fleshy for animal dispersal.

• Attachment to animals.