Plantae

Seed Plants

Vascular Plants

Formation of vascular tissue

– Xylem (water)

– Phloem (food)

– True leaves, roots, and stems Lignin Sporophyte generation dominate

Alternation of Generation

Alternation of Generation Sporophyte dependent on gametophyte

– mosses Large sporophyte and small

independent gametophyte

– ferns Gametophyte dependent on sporophyte

– seed plants

Why be Sporophyte Dominant?

Reduced mutations

– UV light harmful to DNA

– Diploid (2n) form copes better with mutations two alleles

Why Retain Gametophyte Generation?

Ability to screen alleles

– doesn’t require a large amount of energy

Sporophyte embryos rely on some gametophyte tissue

Seeds A seed is a sporophyte in a

package– spores are only single

cells– packaged with food

All seed plants are heterosporous– megasporangia– microsporangia

From Ovule to Seed

Overview of Seed Plants Produce Seeds

– Can remain dormant for years

– Pollination replaces swimming sperm Gametophyte generation reduced

– Gymnosperms lack antheridium

– Angiosperms lack both archegonium and antheridium

Phylogeny

Gymnosperms(Naked Seed)

Division: Cycadophyta Division: Ginkgophyta Division: Gnetophyta Division: Coniferophyta

Ginkgophyta Ginkgo or Maidenhair

Tree Characteristic leaves Only one species Only males are planted

Cycadophyta

Cycads Palm-like plants

– Sago Palms Leaves in cluster at

top of trunks True Secondary

growth

Gnetophyta 3 Genera Ephedra Mormon Tea

– Ephedrine raises heart

rate raises blood

pressure

Coniferophyta

Coniferophyta

Pine tree is the sporophyte generation

Contains both male and female cones– Pollen (staminate)

cones (low in tree) produces pollen

– Ovulate cones (high in tree) with scales

produces seeds

Pine Life Cycle No Antheridium (microsporangia) produce pollen

grain (4 cells)

–2 prothallial cells

–1 generative cell

• become a sterile cell and a spermatogenous cell

• produces 2 sperm

–1 tube cell

–wings for dispersal

Pine Life Cycle Ovule in a ovulate cone

– integument (seed coat) (2n)

– megasporangia (meiosis) or nucellus (nutrition) (2n)

– produces 4 megaspores (3 die) develops into female gametophyte

–archegonium with eggs (n)

Angiosperms

Angiosperm

Flower Sepals Petals Receptacle

Stamen– Anther– Filament

Carpel– Stigma– Style– Ovary with ovule

Angiosperm Life Cycle

Angiosperm Life Cycle No Antheridium (microsporangia)

produce pollen grain

–1 generative cell

• produces 2 sperm

–1 tube cell

Angiosperm Life Cycle Ovule in Ovary

– megasporangia

– produces 4 megaspores (3 die) develops into female gametophyte

called the embryo sac

Angiosperm Life Cycle Inside embryo sac

– 7 cells (eight nuclei) due to 3 mitotic divisions 3 antipodals 2 polar nuclei (one cell) 2 synergids 1 egg

Angiosperm Life Cycle Double fertilization

– one sperm unites with egg

– one sperm unites with polar nuclei develops into endosperm (3n)

Fruit and Seed development

– ovule = seed

– ovary = fruit

Cross Pollination

Most flowers do not self-pollinate

– stamen and carpal may develop at different times

– stamen and carpal may be arranged in flower to avoid contact

Angiosperm Radiation

Begins the Cenozoic era (65 mya) Most closely related to the Gnetophyta Coevolution

– the mutual influence of two species on each other

– plants and animals (insects, birds, bats)

Pollination

Dispersal

The Global Impact

Transformed atmosphere

– reduced carbon dioxide

– cooled the earth Nonrenewable resource