lecture 5

• Challenges posed by life on land


  • Staying hydrated: water evaporates quickly in air, raising danger of desiccation
  • Acquiring and distributing water: By not being available to all cells directly, need a water distribution system
  • Building support: without water, no buoyancy
  • Fertilization: How will motile gametes meet up for reproduction?
• Alternation of generations


  Haplodiplontic life cycle with a multicellular haploid gametophyte and a multicellular diploid sporophyte
• Embryophytes (land plants)


  • Nonvascular plants (bryophytes)
  • Vascular seedless plants (lycophytes, monilophytes)
  • Seed plants (gymnosperms, angiosperms)
• Bryophytes


  • Gametophyte dominates the life cycle
  • Lack vascular tissue for long-distance water transport
  • Rhizoids and phyllids for water/nutrient absorption and anchoring
  • Gametangia protect gametes and developing embryo
  • Sporophyte dependent on gametophyte for nutrition
• Lichens


  Provide initial soil for early land plants
• Mycorrhizal fungi


  Enhance land plants' capacity to obtain nutrients from soil
• Arbuscular mycorrhizal fungi were likely present early and essential for land plant colonization
• Molecular and morphological traits support the charophyte algae as the closest algal relatives of land plants
• Rational


  (in classical economic theory) economic agents are able to consider the outcome of their choices and recognise the net benefits of each one
• Rationality in classical economic theory is a flawed assumption as people usually don't act rationally
• Marginal utility


  The additional utility (satisfaction) gained from the consumption of an additional product
• If you add up marginal utility for each unit you get total utility
• Diploid (2n)


  Containing two sets of chromosomes
• Sperm


  Male gamete
• "Bud"


  Undifferentiated mass of cells that can develop into a new organism
• Antheridia


  Male gametophyte
• Male


  Producing male gametes
• Gametophyte (n)


  Haploid multicellular organism that produces gametes
• Egg


  Female gamete
• Spores


  Reproductive units capable of developing into a new individual
• Spore dispersal


  The spreading or distribution of spores
• Peristome


  Structure around the opening of a moss capsule that controls spore release
• FERTILIZATION


  Fusion of male and female gametes
• Seta


  Stalk that supports the capsule in mosses
• Capsule (sporangium)


  Structure that contains spores
• Foot


  Structure that attaches the sporophyte to the gametophyte
• Embryo


  Zygote that has begun to develop
• Archegonium


  Female reproductive structure in bryophytes
• 2 mm
• Zygote (2n)


  Diploid cell formed by the fusion of male and female gametes
• Archegonia


  Female gametophyte
• Protonemata (n)


  Filamentous stage of the gametophyte in mosses
• Rhizoid


  Hair-like structure that anchors and absorbs water and nutrients for the gametophyte
• Sporangium


  Structure that contains spores
• MEIOSIS


  Cell division that produces haploid spores from diploid cells
• Mature sporophytes


  Diploid multicellular organism that produces spores
• Capsule (LM)


  • Microscopic image of a moss capsule

  
• Female gametophytes


  Haploid multicellular organism that produces female gametes
• Young sporophyte (2n)


  Developing diploid multicellular organism that produces spores
• Key Life Cycle Innovations


  • Rhizoids and Phyllids
  • Gametangia
  • Retained Embryos
  • Waterproofed Sporophytes and Spores