greening of the land

• Origin of land plants: 450 million years ago, land plants appeared in the fossil record
• Land plants: Embryophytes
• Evidence of life 1.1 BYA in the nonesuch shale michigan.
• little evidence of multicellular 1.1bya
• 1bya torridonian west scotland. degrees of spacial organisation. clustering of simple organisms
• 1bya subareal exposure signs
• Cell walls and enveloping= adaptation to prevent desiccation
• protoembryophytes = early evolution stage
• Thallus: a plant body that is not differentiated into stem and leaves and lacks true roots and a vascular system. Thalli are typical of algae, fungi, lichens, and some liverworts.
• palynology: the study of pollen grains and other spores, especially as found in archaeological or geological deposits. Pollen extracted from such deposits may be used for radiocarbon dating and for studying past climates and environments by identifying plants then growing.
• palynology evidence of bryophytes 495mya
• Spores with tri-leaf mark are indicative of vascular plants starting rom around 450MYA
• Why spores to date evolution

  Well preserved and chemical signals saved
• Non vascular collinisation 270MYA
• Macrofossils in 425mya.
• Challenges of leaving the water

  Water free reproduction-Motile gametes

  Modify life cycle

  protection against descication

  mechanical support (3D)

  Cells for water and nutrient uptake

  Anchorage

  UV-B radiation
• Water free reproduction involved evolving spores. Spores are small, lightweight, and can survive in the environment.
• Sporopollenin provides:


  Microbiol protection

  chemical protection

  physical protection

  UV-B protection
• Alternation of generations: two stages of life cycle Gametophyte and sporophyte
• Bryophytic organisms are Haploid dominant with the majority of their lifecycle being gametophytic and micropore
• Protection agaisnt dessication- cuticle for vascular plants. thick biopolymer that provides a waterproof coating. stomata to allow for gas exchange
• Mechanical support: provided by lignin and phenolic acids
• Terrestrialization: adaptation to living on land
• Vascular tissue: xylem and phloem
• PAR: photosynthetic active radiation
• UV-B: 280-315nm, mostly absorbed by the ozone but extremely harmful. Causes cancers and mutations
• UV-B damage

  Protein, membrane and DNA destruction