Week 1 | Day 2 | BIOA02

Week 1 | Day 2 | BIOA02

• Adapted better than bryophyte outside of water because of these characteristics:
  • Cuticles
    • Waxy layer that helped retain water
  • Stomata
    • Because they’re outside of water, they need ‘breathing ports’ to take in CO2 and take out water
    • Stoma made up of 2 guard cells <- like this
  • Vascular tissue

Diversity of Lycophytes

3 groups:

1. Clubmosses (400 species)
2. Quillworts (150 species)
3. Spikemosses (700 species)

Ferns (3 groups)

1. Whisk ferns (2 species)
2. Horsetails (15 species)
3. True ferns (2000 species)
   • 75% of species found in tropics

Life Cycle of Ferns (Same as Lycophytes)

• Diploid (sporophyte) is dominant/most seen in this state
  • Bryophytes is the opposite (gametophyte is dominant)

Sorus can be found on underside of leaves

• Prothallium used for sexual reproduction
  • Grows 2 structures: female is archegonia, male is antheridia
  • They can self-fertilize by just transferring antheridia spermatozoids to the female counterpart

• The two generations are ‘independent’ (aka sporophyte can do its own photosynthesis after a bit)
• Male gamete (spermatozoid) self-propelled over short-distances
• Spores can disperse over long distances
• Prothallium does not have a cuticle, meaning it still heavily depends on water

Gymnosperm

5 groups:

1. Conifers (900 species)
2. Ginkgo (1 species)
3. Ephera (35 species)
4. Welwitschia (1 species)
5. Gnetum (35 species)

1. Conifers (in latin: ‘cone-bearing’)

• Male and females short lived after they give their pollen/seeds BUT…
  • It takes a female cone 2 years to disperse its seeds

Key Invention: Wood

• Wood did not exist before gymnosperms
  • Allowed gymnosperms to grow gigantic and be protected

Angiosperm (in Latin: Covered Seeds)

• Do not produce through cones, instead uses flowers
• Sporophyte is dominant over gametophyte

Sporophyte Feeds the Gametophyte

Interpretation of Life Cycle (gymno and angiosperm)

• Gametophyte totally dependent on sporophyte
• Male gametophyte (pollen) moved over short/long-ish distances = pollination syndrome
• Seeds dispersed over long distances = seed syndrome

Tree of Life - Key Evolutionary Inventions

Photosynthetic Summary

• Bryophytes: gametophyte feeds sporophyte
• Lycophytes/ferns: both generations are photosynthetic
• Gymnno/angiosperms: sporophyte feeds gametophyte

Mobility of Life Cycle Phases Summary

Dependence on Water