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

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