Evolution of Angiosperms
Chapter 20
Archaefructus sinensis
Rafflesia arnoldii
True or False
1) Flowers are the
reproductive
structures of
angiosperms.
2) Flowers are
determinate shoots
that bears
sporophylls.
Evolutionary Trends Among Flowers
1) 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 sixcarbon 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
Axile
Free central
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.