BOT 14 - 6 - Evolution of Angiosperms and Their Reproductive Features

• Complex xylem - incl. vessels and parenchyma

• Complex phloem - sieve tube elements w/companion cells

• flower

• closed carpels

• 8-nucleate megagametophyte

• 3-nucleate microgametophyte

• stamens with 2 pairs of pollen sacs

• Double fertilization and formation of triploid endosperm

• Ovary to protect ovules ("seeds in vessels")

• Advanced pollination syndromes - insects, birds, etc.

• Fruits to protect and disperse seeds

Angiosperm Apomorphies

Accessory parts (perianth)

1. Sepals (calyx)

2. Petals (corolla)

Essential parts

1. Stamen (androecium)

2. Pistil/Carpel (gynoecium)

What are the accessory and essential parts of the angiosperm apomorphy:

Flower and closed carpels

Explain the evolution of the carpel.

Explain the evolution of the stamen.

1. Pollen grain lands on the stigma and germinates; the pollen tube grows into the style.

2. Two sperm nuclei travel through the pollen tube to the ovary.

3. One sperm nucleus fuses with the egg nucleus to form a diploid zygote.

   • The other sperm nucleus fuses with two nuclei in the central cell to form the triploid endosperm.

Explain the Angiosperm Apomorphies:

Double fertilization and formation of triploid endosperm

• Pollen grains (reduced male gametophyte)

• Embryo sac (reduced female gametophyte)

• ______________ (reduced male gametophyte)

• ______________ (reduced female gametophyte)

Pollination

It is the transfer of pollen grains from the stamen to the pistil that is facilitated by wind or pollinators

late Devonian

Early seed plants appeared during the __________ period

Mesozoic

Gymnosperm dominated during the __________

Cretaceous; 140

Angiosperm 1st fossil record was during the ___________,  ______ MYA

90

Worldwide dominance in vegetation was ______ MYA

75

Many modern families and some modern genera existed ____ MYA

many indefinite; fewer; definite

Evolutionary Trends Among Flowers

Flowers have gone from ______ ________ parts to having _______ parts that are _________ in number.

Floral whorls are one of the layers of modified leaves that make a flower; a complete flower has four whorls: sepals, petals, stamens, and pistil from base to top.

Evolutionary Trends Among Flowers

Floral _________ have reduced over time.

Evolutionary Trends Among Flowers

Floral parts have become ________.

Evolutionary Trends Among Flowers

Floral axes have become ___________.

leaflike and incompletely closed; pistil-shaped and sealed

Evolutionary Trends Among Flowers

Carpels have gone from _____________ to _______________.

superior; inferior

The ovaries went from above the sepal to below it.

Evolutionary Trends Among Flowers

Ovaries have gone from _________ to _________

indistinct sepals and petals; distinct calyx and corolla

The sepal and petals are on the same plane.

Evolutionary Trends Among Flowers

Perianths have gone from having _____________ to having a _______________.

radial; actinomorphic; bilateral; zygomorphic

Evolutionary Trends Among Flowers

Flowers have gone from ________ (___________) to ________ (___________) symmetry