Archaeplastida

• Organisms


  • Diplomonads
  • Parabasalids
  • Euglenozoans
  • Dinoflagellates
  • Apicomplexans
  • Ciliates
  • Diatoms
  • Golden algae
  • Brown algae
  • Oomycetes
  • Cercozoans
  • Forams
  • Radiolarians
  • Red algae
  • Chlorophytes
  • Charophytes
  • Land plants
  • Slime molds
  • Gymnamoebas
  • Entamoebas
  • Nucleariids
  • Fungi
  • Choanoflagellates
  • Animals
  • Alveolates
  • Stramenopiles
  • Green algae
  • Amoebozoans
  • Opisthokonts
  • Excavata
  • Chromalveolata
  • Rhizaria
  • Archaeplastida
  • Unikonta

  
• Supergroup Archaeplastida

  • Monophyletic group
  • Chloroplasts origin: primary endosymbiosis with a cyanobacterium
  • Cells typically lack centrioles
  • Cell wall compose of cellulose
  • Store food: starch (of various types)
• Kingdoms in Supergroup Archaeplastida

  • Rhodoplantae (Red algae)
  • Viridiplantae (green algae, land plants)

  
• Phylum Rhodophyta (red algae)


  • Unicells to complex filaments and parenchymatous thalloid plants
  • Mainly of warm marine habitat
  • With phycobilin pigments
  • Chlorophyll a (absence of b or c)
  • No flagellate stages
  • Food stored: floridean starch (alpha 1,4 glucan), similar to cyanophycean starch of the Cyanobacteria

  
• Classes in Phylum Rhodophyta

  • Florideophyceae

  
• Orders in Class Florideophyceae

  • Ceramiales

  
• Families in Order Ceramiales

  • Rhodomelaceae

  
• Polysiphonia (red algae)


  • Mostly branched, filamentous
  • Attached by rhizoids or haptera
  • Thallus consists of fine branched filaments
  • Central axial filament
  • Supporting pericentral cells = 4–24

  
• Polysiphonia reproduction


  1. Typically diplohaplontic -- alternation of haploid and diploid stages; some are haplontic

  2. Oogamous: female gametophyte with carpogonium containing the egg with receptive surface called trichogyne; male gametophyte produce spermatia (non-motile cells that function as male gametes)

  3. Triphasic life cycle: gametangial, carposporangial and tetrasporangial phases

  
• Gametangial phase - gametophyte phase (n): male gametophyte produce spermatia, female gametophytes produce carpogonium with female gamete; after fertilization, diploid nucleus migrates and fuses with supporting cell in carpogonium
• Carposporophyte phase - diploid phase, origin: zygote, entirely parasitic on parent female gametophyte, produces non-motile diploid carpospores

  
• Tetrasporophyte phase - develops tetrasporangium, produces tetraspores after meiosis, spores settle and grow to become male and female gametophyte plants

  
• Ecology of red algae

  • Mostly marine, a few freshwater
  • Typically live attached to surfaces
  • Light harvesting is very efficient, can live at tremendous depths due to phycoerythrin accessory pigments
  • Coralline red algae can build up calcium carbonate in their cell walls, and can be reef-building organisms

  
• Economic importance of red algae

  • Agar-agar is a jelly-like food delicacy in Japan
  • Agar used as culture medium in microbiology (cannot be digested by most microorganisms)
  • Agarose -- purified from agar – used in molecular biology (gel electrophoresis)
  • Paper thin glossy sheets of nori: mineral rich wrap for rice, vegetable and seafood in sushi

  
• Ecological importance of red algae

  • Corallines (calcified red algae) help build and maintain coral reefs, consolidate and stabilize reef crests, protect reefs from wave damage
  • Regarded as keystone organisms - species whose decline could cause the collapse or loss of entire biotic communities
• Phylum Glaucophyta


  • Freshwater habitat
  • Coccoid and occur in loose colonies formed by the persistent cell wall of the parent cell following division
  • Have mitochondria with flat cristae
  • Chloroplasts known as 'cyanelles' with peptidoglycan layer (relic of endosymbiotic origin from cyanobacteria)
  • Plastids contain chlorophyll a and phycobilins organized into phycobilisomes
  • Motile forms have two unequal flagella, which may have fine hairs

  
• Classes, Orders, Families in Phylum Glaucophyta


  • Class Glaucocystophyceae; Order Glaucocystales; Family Glaucocystaceae

  
• Kingdom Viridiplantae


  • Comprise the green algae and land plants
  • Common synapomorphies: cell walls containing cellulose, chloroplasts containing chlorophylls a and b, food stored in the form of starch, typically have mitochondria with flat cristae

  
• Subgroups in Kingdom Viridiplantae

  • Chlorophyta (chlorobiont clade) - green algae
  • Streptophyta (streptobiont clade) - Charophyta, Embryophyta (bryophytes, seedless and seeded vascular plants)

  
• Differences between Chlorobionts and Streptobionts

  • Mitosis: Chlorobionts generally with centrioles (centric) and closed (nuclear envelope remains intact), Streptobionts no centrioles (acentric) and open (nuclear envelope breaks down)
  • Cytokinesis: Chlorobionts have phycoplast, Streptobionts have phragmoplast
  • Flagellar insertion: Chlorobionts at the apex, Streptobionts subapical
• Phylum Chlorophyta (green algae)


  • Includes most of the green algae
  • May grow as colonies, unicells, filaments, and large seaweeds
  • Occur in almost all types of water and often are dominants in freshwater environments
  • Some are terrestrial species

  
• Ulva (sea lettuce)


  • Flat expanded sheet
  • Asexual reproduction by biflagellated zoospores
  • Sexual reproduction isogamous with alternation of diploid and haploid isomorphic generation
• Chlamydomonas (sea cockroach)


  • Asexual - motile unicellular algae, oval in shape, cell wall of glycoprotein and non cellulosic polysaccharides, with prominent cup or bowl shaped chloroplast, pyrenoid with starch sheath, 2 anterior flagella (whiplash; 9+2 arrangement)
  • Sexual - gametes fuse to form zygote, which undergoes meiosis to produce mature cells

  
• Volvox


  • Composed of numerous flagellate cells similar to Chlamydomonas, up to 50,000 in total
  • Cells are embedded in the surface of a hollow sphere or coenobium containing an extracellular matrix made of a gelatinous glycoprotein
  • Asexual reproduction by repeated mitotic division of zooids to form daughter colonies
  • Sexual reproduction by differentiation of some zooids into macrogametes or microgametes, which fuse after release from the parent colony

  
• 50,000 cells are embedded in the surface of a hollow sphere or coenobium containing an extracellular matrix made of a gelatinous glycoprotein
• Asexual reproduction


  1. Repeated mitotic division of one of the cells (zooids) to form a hollow sphere of cells, with the flagellated ends of the cells inside

  2. The sphere then turns itself inside out to form a daughter colony similar to the parent colony

  3. Several daughter colonies are formed inside the parent colony before they escape by rupture of the parent
• Sexual reproduction


  1. Some of the zooids differentiate into macrogametes or microgametes

  2. Macrogametes are fewer and larger and are loaded with food for nourishment of the young organism

  3. Microgametes, by repeated division, form flagellated sperms that leave the mother organism and swim about to find a mature ovum

  4. After fertilization, the zygote secretes a hard, spiny, protective shell around itself

  5. When released by the breaking up of a parent, a zygote remains dormant during the winter

  6. Within its shell the zygote undergoes repeated division, producing a small organism that breaks out in the spring
• Volvox sp.


  • Pandorina
  • Eudorina
• Pandorina


  • Composed of 8, 16, or sometimes 32 cells, held together at their bases surrounded by mucilage
• Eudorina


  • Composed of 16 or 32 spherical biflagellate cells loosely aggregated into a globular shape within a mucilage envelope
• Oedogonium


  • Filamentous; cells uninucleate
  • Sexual reproduction is oogamous; with flagellated zoospores
  • Only certain cells can divide, with stacks of old cell walls (called apical caps) at the cell apex
• Phylum Charophyta is a group of green algae with characteristics in common with the land plants, including phragmoplast formation, cell plate, and sexual reproduction without flagellated gametes (except in the stoneworts)

  
• Chara (Muskgrass/stoneworts)


  • Multicellular
  • Superficially resemble land plants because of stem-like and leaf-like structures
  • The stem consists of nodes and internodes
  • Typically anchored to the substrate by means of branching underground rhizoids
  • Rough to the touch because of deposited calcium salts on the cell wall
  • Asexual reproduction takes place by tubers, and secondary protonema
  • Sexual reproduction involves a globule or antheridium (male) producing biflagellated antherozoids (sperm), and a nucule or archegonium (female) with an oogonium (containing an egg/ovum)
• Class Zygnematophyceae


  • Filamentous or unicellular forms
  • Reproduction involving conjugation between 2 cells
  • No flagellated stages in the life cycle
  • All are fresh water algae

  
• Order Cosmariales


  • Micrasterias furcata
  • Closterium sp.
• Closterium sp.


  • Variously shaped unicells; usually 2 chloroplasts with nucleus sited between them; often with a narrow isthmus; mobility by mucilage secretion
• Order Zygnematales


  • Unbranched, filamentous forms
  • With varied forms of chloroplasts
  • Cell wall usually slimy
  • Conjugation results in the formation of a resistant zygospore
• Zygnema


  • Freshwater habitat; filamentous, free-floating or anchored with a holdfast; composed of elongate barrel-shaped cells, each with two star-shaped chloroplasts arrayed one after the other along the axis of the cell

  
• Spirogyra


  • Unbranched with cells connected end to end in long green filaments
  • With spiral arranged chloroplasts
  • Cell wall layers: outer wall= pectin, inner wall = cellulose
  • Pyrenoids = centers for starch production
  • Asexual reproduction = fragmentation and mitosis to form new filaments
  • Sexual Reproduction = conjugation and formation of zygospore, with two forms: scalariform conjugation between two filaments, and lateral conjugation between two adjacent cells on the same filament

  
• Meiosis in Spirogyra


  1. Meiosis forms 4 haploid nucleus (only one survives and others disintegrate)

  2. The zygospore bursts open to form a germ tube

  3. The germ tube divides repeatedly by transverse division and develops into a new haploid filament of Spirogyra