Plantae Seed Plants Vascular Plants Formation of vascular

Plantae Seed Plants

Vascular Plants Formation of vascular tissue – Xylem (water) – Phloem (food) – True leaves, roots, and stems l Lignin l Sporophyte generation dominate l

Alternation of Generation

Alternation of Generation Sporophyte dependent on gametophyte – mosses l Large sporophyte and small independent gametophyte – ferns l Gametophyte dependent on sporophyte – seed plants l

Why be Sporophyte Dominant? l Reduced mutations – UV light harmful to DNA – Diploid (2 n) form copes better with mutations utwo alleles

Why Retain Gametophyte Generation? Ability to screen alleles – doesn’t require a large amount of energy l Sporophyte embryos rely on some gametophyte tissue l

Seeds l l 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 l Gametophyte generation reduced – Gymnosperms lack antheridium – Angiosperms lack both archegonium and antheridium l

Phylogeny

Gymnosperms (Naked Seed) Division: l Cycadophyta Ginkgophyta Gnetophyta Coniferophyta

Ginkgophyta l l Ginkgo or Maidenhair Tree Characteristic leaves Only one species Only males are planted

Cycadophyta l l Cycads Palm-like plants – Sago Palms Leaves in cluster at top of trunks True Secondary growth

Gnetophyta l l l 3 Genera Ephedra Mormon Tea – Ephedrine uraises heart rate uraises blood pressure

Coniferophyta

Coniferophyta l l Pine tree is the sporophyte generation Contains both male and female cones – Pollen (staminate) cones (low in tree) u produces pollen – Ovulate cones (high in tree) with scales u produces seeds

Pine Life Cycle l 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 l Ovule in a ovulate cone – integument (seed coat) (2 n) – megasporangia (meiosis) or nucellus (nutrition) (2 n) – produces 4 megaspores (3 die) udevelops into female gametophyte –archegonium with eggs (n)

Angiosperms

Angiosperm

Flower l l l Sepals Petals Receptacle l l Stamen – Anther – Filament Carpel – Stigma – Style – Ovary with ovule

Angiosperm Life Cycle

Angiosperm Life Cycle l No Antheridium (microsporangia) uproduce pollen grain – 1 generative cell • produces 2 sperm – 1 tube cell

Angiosperm Life Cycle l Ovule in Ovary – megasporangia – produces 4 megaspores (3 die) udevelops into female gametophyte called the embryo sac

Angiosperm Life Cycle l Inside embryo sac – 7 cells (eight nuclei) due to 3 mitotic divisions u 3 antipodals u 2 polar nuclei (one cell) u 2 synergids u 1 egg

Angiosperm Life Cycle Double fertilization – one sperm unites with egg – one sperm unites with polar nuclei udevelops into endosperm (3 n) l Fruit and Seed development – ovule = seed – ovary = fruit l

Cross Pollination l 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) l Most closely related to the Gnetophyta l Coevolution – the mutual influence of two species on each other – plants and animals (insects, birds, bats) l

Pollination

Dispersal

The Global Impact Transformed atmosphere – reduced carbon dioxide – cooled the earth l Nonrenewable resource l