Protists, nonvascular plants

• Dinoflagellates

  • mostly unicellular, approximately 50% photoautotrophic
  • important members of the marine and freshwater food chains
  • 4000 living species
  • most are plankton (free-drifting in mates)
  • covered with silicate-based shells (cellulose and silitate)
  • when it reaches condition for it to proliferate 'red-tide' occur
• red-tide

  • harmless
  • occasionally produces toxic substance
  • outcome: death toll on other species in the environment can be very high
• Algae

  • plant-like protists, photoautotrophs
  • mostly multi-cellular
  • red, green and brown
  • responsible for fixing half of the world's carbon, liberating oxygen
• Brown Algae (Kelp)

  • multicellular, sometimes diploid state, sometimes haploid
  • emulsifiers in many products
  • photosynthetic
  • has chlorophyll 'c' and 'a'
• green algae

  • photosynthetic, multicellular
  • probably the ancestor to land plants
  • able to trap light during photosynthesis: cell walls, chlorophyll
  • chlorophyll 'a' and 'b'
  • found in fresh-water environments
  • inhibits very moist terrestrial environments
• eukarya and archaea

  • histones
  • RNA polymerase
• Diversity among protists

  1. multi-cellularity: most are unicellular but some are complex multi-cellular organisms
  2. Chlorophyll: all eukaryotic autotrophic algae contain chlorophyll 'a' - a chemical that capture light energy for photosynthetic reaction
  3. Green Algae: plants evolved from a green algal ancestor - shares many similarities with land plants
  4. alternation of generations: life-cycle that consists of a multicellular diploid phase and a multicellular haploid phase
  5. two folds cost: one offspring needs two parents when there is sex (meiosis), one parent no sex (mitosis) -- less alternations
• Alternation of generations for algae

  1. sporophyte (2n) goes through meiosis to produce spores
  2. spores are haploid (n) and go through mitosis to create separate gametophytes
  3. mitosis: male and female gametophytes are separate (n) through mitosis creates gametes (n)
  4. mitosis of gametes creates egg and sperm (n)
  5. fertilization of egg and sperm create zygote (2n)
  6. mitosis of the zygote creates a sporophyte (2n)
  7. then mitosis creates a more mature sporophyte (2n)
• important points of algae life-cycle

  • spores are motile, they swim
  • gametes can also swim
  • water is important for the reproduction of algae
  • water provide nutrients, and gives the sperm the ability to swim to egg
• sporophyte: diploid multicellular form that produces spores by meiosis
• spores: haploid cells that multiply by mitosis to generate a multicellular haploid form
• gametophyte: a haploid multicellular form that produces gametes
• egg and sperm are haploid gametes
• zygote is the result of fertilization (syngamy) between egg and sperm
• embryo is what the zygote develops into and (diploid) develops into the sporophyte
• The origin of Land Plants

  • evolved on the order of 475 mya
  • multicellular eukaryotes successfully invaded land
  • biodiversity was restricted to the ocean for billions of years
  • most major animal phyla evolved before there were plants
• land plants are multicellular photosynthetic autotrophic eukaryotes that can survive and reproduce on land
• Plants invade land

  • sexual reproduction happens on land not water (embryophyte - embryo bearing plant)
  • the ability to survive on land in contact with air
• key formation of land plants

  • waxy cuticle layer: helps a plant retain moisture
  • stomata: series of pores for gas exchange
  • vascular tissue formed due to a heterogeneous environment
• 4 major groups of land plants (all contain: waxy cuticle layer, stomata)

  1. Non-vascular tissue: no vascular tissue
  2. seedless vascular plants: no seeds, but has vascular tissue
  3. Gymnosperms: have seeds and vascular tissues and gametophytes
  4. angiosperms: seeds, vascular tissue, flowers and fruit
• common ancestor of land plants

  • cuticles, stomata and embryophyte
• land plants years of evolution

  1. origin of plants 475 mya
  2. Silurian-Devonian explosion 416 mya
  3. Seedless vascular plants (carboniferous, Lycophytes, horsetails) 359 mya
  4. Gymnosperms abundant 299 mya
  5. angiosperms 145 mya
• Nonvascular plants

  • first group of plants: moss
  • liverworts, marchantia polymorpha, embryophyte
  • able to live on land
• Main alternation of generation in nonvascular plants

  1. gametophyte is dominant: physically attached to gametophyte
  2. male and female gametophyte are independent
  3. sperm form antheridium
  4. egg and the zygote form archegonium
  5. fertilization still requires water