History of plant evolution

1
Plant reproductive modes

• History of plant evolution

• Adaptations for terrestrial life (ancestors were
  multicellular green algae)

• Plants had to overcome need for water to

• Reproduce

• Provide structural support

How are new organisms produced?
2
Plant reproductive modes

• Simple plant taxonomy

• 12 living phyla (divisions) of plants

• 3 phyla are non-vascular (no specialized cells
  for transport of water and carbohydrates such as
  xylem or phloem)

• Phylum Bryophyta (mosses)

• 9 phyla are vascular (plants with vascular tissue)

• Seedless vascular plants

• Phylum Pterophyta (ferns)

• Seed plants

• Gymnosperms (Phylum Coniferophyta) plants with
  ovules exposed at fertilization

• Angiosperms (Phylum Anthophyta) plants with
  ovules enclosed within flower tissue at
  fertilization

How are new organisms produced?
3
Plant reproductive modes

• Evolutionary pattern seen in reproductive modes
  of plants

• Less reliance on water

• Increasing protection of embryo

• Reduced haploid stage of life cycle

• All plant life cycles are haplodiplontic ( both
  haploid and diploid stages are multicellular)

• Animal life cycles are diplontic ( only diploid
  stage is multicellular)

How are new organisms produced?
4
Plant reproductive modes

• Generalized life cycle of plants

egg
Haploid stage
Gametophyte
(gamete-producing, haploid plant)

sperm
Gametangia (structure where gametes
produced)
spores
Spore mother cell (diploid
cell that undergoes meiosis to produce haploid
spores)
zygote
embryo
Sporangia (structure where spores produced)
Sporophyte
(spore-producing, diploid plant)
Diploid stage
How are new organisms produced?
5
Plant reproductive modes

• Comparison of reproductive modes of plants

• Nonvascular plants (e.g. Phylum Bryophyta)

• Small, unspecialized plants (no true leaves or
  roots)

• Sporophyte attached and (usually) nutritionally
  dependent on dominant gametophyte

• Reproduction completely dependent on water

How are new organisms produced?
6
Plant reproductive modes

• Comparison of reproductive modes of plants

• Nonvascular plants (e.g. Phylum Bryophyta)

How are new organisms produced?
7
Plant reproductive modes

• Comparison of reproductive modes of plants

• Seedless vascular plants (e.g. Phylum Pterophyta)

• More specialized plants (true leaves and roots)

• Sporophyte dominant stage of life cycle
  gametophyte reduced (unspecialized) and
  independent

• Reproduction completely dependent on water

• Embryo slightly protected in archegonia

How are new organisms produced?
8
Plant reproductive modes

• Comparison of reproductive modes of plants

• Seedless vascular plants (e.g. Phylum Pterophyta)

How are new organisms produced?
9
Plant reproductive modes

• Comparison of reproductive modes of plants

• Other seedless vascular plants with similar life
  cycles

How are new organisms produced?