Plantae Seed Plants. Vascular Plants l Formation of vascular tissue –Xylem (water) –Phloem...
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Transcript of Plantae Seed Plants. Vascular Plants l Formation of vascular tissue –Xylem (water) –Phloem...
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