biology 20-4 Plantlike Protists

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biology 20-4 Plantlike Protists Powered By Docstoc
					Plantlike Protists: Red, Brown,
       and Green Algae
                     Algae
• Plant like
• Most are multicellular
• Have reproductive
  cycles similar to
  plants
• Many have cell walls
  and photosynthetic
  pigments
• Many possess high
  specialized tissues
                   Red Algae
• Members of the phylum
  Rhodophyta (red plants)
• Able to live at great
  depths due to their
  efficiency in harvesting
  light energy
• Red algae contain
  chlorophyll a and reddish
  accessory pigments
  called phycobilins
• Found all throughout the
  world
• Phycobilins are especially
  good at absorbing blue
  light, enabling red algae to
  live deeper in the ocean
  than many other
  photosynthetic algae
    – Found from surface to
      depths of up to 260
      meters
• Many red algae are actually
  green, purple, or reddish
  black depending upon the
  other pigments they contain
• Most are multicellular
• All have complex life
  cycles
• Lack flagella and
  centrioles
• Play an important role
  in the formation of
  coral reefs
• Supply nourishments
  to coral
               Brown Algae
• Belong to the phylum
  Phaeophyta (dusky
  plants)
• Contain chlorophyll a
  and c, as well as a
  brown accessory
  pigment
• Largest and most
  complex algae
• Multicellular
• Most are marine
• Found in cool shallow
  coastal water of the
  temperate or arctic
  waters
• Largest known alga is
  giant kelp
• Can grow up to 60
  meters!
• Forms mats
  kilometers long!
• One of the most common is
  Fucus (rockweed)
• Found along the rocky coast of
  the eastern United states
• Has a holdfast structure that
  attaches the alga to the bottom
• Flattened stemlike structures
  called stripes
• Leaflike structures called
  blades
• Gas-filled swellings called
  bladders which keep the alga
  upright
                   Green Algae
• Are members of the phylum
  Chlorophyta (green plants)
• Share many characteristics
  with plants
   – Photosynthetic pigments
     (chlorophyll a and b)
   – Cell wall compositions
     (have cellulose)
   – Store food in the form of
     starch
• Scientists believe that green
  algae are the ancestors of
  modern land plants
• Are found in fresh and
  slat water and even in
  moist areas on land
• Many species live most of
  their lives as single cells
• Other form colonies
  (groups of similar cells)
• A few are multicellular
  and have well-developed
  specialized structures
• Unicellular green algae
   – Ex. Chlamydomonas
   – Grow in ponds, ditches,
     and wet soil
   – Is a small egg-shaped cell
     with two flagella and a
     single large, cup-shaped
     chloroplast
   – Within the base of the
     chloroplast is a region that
     synthesizes and stores
     starch
   – Lacks large vacoules has
     two small contractile
     vacoules
• Colonial green algae
  – Ex. Spirogyra
     • Found in freshwater
     • Forms long threadlike
       colonies called
       filaments
  – Ex. Volvox
     • Eleaborate colonies
       with 500-50,000 cells
       arranged in hollow
       spheres
     • Coordinates movement
• Multicellular green algae
   – Ex. Ulva
   – “Sea lettuce”
   – Commonly found along
     rocky seacoasts
   – True multicellular organism
     containing several
     specialized cell types
   – Only two cells thick but
     tough enough to survive
     pounding waves
   – A group of cells at its base
     form holdfasts that attach
     Ulva to the rocks
  Reproduction in Green Algae
• The life cycles of many algae include both
  a diploid and a haploid generation
• Many algae switch back and forth between
  haploid and diploid stage during their life
  cycles, in a process known as alternation
  of generations
• Many species also shift back and forth
  between sexual and asexual reproduction
Reproduction in Chlamydomonas
Reproduction in Chlamydomonas
Reproduction in Ulva
Reproduction in Ulva
         Human uses for algae
• Food source
• Algae produces much of
  the world’s oxygen
• Medicines and vitamins
• Thickener in ice cream
  from brown algae called
  algin
• Sushi rolls use red algae
  as a wrapper
• Chemical industry uses
  for manufacturing

				
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