Algal Diversity: Autotrophic “protists”
Haptophytes, Cryptomonads, Dinoflagellates,
Euglenoids
Photosynthetic Heterokonts
Chrysophyceae: the golden algae
Xanthophyceae: the yellow-green algae
Phaeophyceae: the brown algae
Bacillariophyceae: the diatoms
Heterotrophic Heterokonts
Oomycota: the water molds
Algal Diversity
Organisms known as “algae” belong to several different lineages.
Algal Diversity
“Heterokonts”
Bacillariophyceae (diatoms)
Chrysophyceae ( golden algae)
Xanthophyceae (Yellow-green algae)
Phaeophyceae (brown algae, “seaweeds”)
“Heterokonts” (= Stramenopiles)
2 different types of flagella (smooth, hairy/tinsel)
(often only present during sexual reproduction, on “male” gametes)
Dinoflagellates, Euglenoids,
Dinoflagellates are autotrophic; Euglenoids vary
Haptophytes and Cryptomonads
?
Algal Diversity
Red and Green Algae: the “land plant” lineage
Primary Endosymbiosis occurred in a common ancestor of this lineage.
Evolution of Multicellularity
Characteristics of “Algae”
• Photosynthetic (Autotrophic)
• Function like plants ecologically.
• Phycology = study of algae
Highly diverse in form
• Many unicellular
• Some multicellular
- colonial
- filamentous (branched or not)
- multinucleate masses
- some with differentiated organs (macroalgae)
marine phytoplankton
• Vary in size from microscopic to 30 meters long.
Ecology of “Algae”
Microscopic/unicellular algae and cyanobacteria are phytoplankton.
•Basis of the food chain in marine and freshwater ecosystems
• Fix atmospheric CO2 into organic molecules (~30% of Earth’s primary production?)
Macroalgae have similar roles.
- some occur in intertidal
zones
- exposed to air twice each
day
- adaptations that allow them
to survive fluctuations of
humidity, temperature,
light, and pounding surf
Food for humans:
“Kombu” = kelp (brown algae)
“nori” = red alga
Alginates: gelatinous/mucilaginous components of some algal cell walls used in foods,
pharmaceuticals, cosmetics as thickening agents, drying agents, colloid stabilizers
Ex. Agar, carageenan
Euglenoids
•Chloroplasts similar to those of green algae and land plants.
•Secondary endosymbiosis: a common ancestor of some Euglenoids ingested a green algae
as a symbiont.
• Flagellated unicells: swim
• Most Euglenoids are heterotrophic
• No cell wall; flexible or rigid
protein “pellicle”
• Eyespot senses light
• Chloroplast degenerates in dark;
organisms becomes heterotrophic
and feeds by phagocytosis.
Cryptomonads
• Single-celled flagellates
• Marine
• Chloroplast structure and pigments
suggest
secondary endosymbiosis of red
algae
• Ecologically important
phytoplankton
• Dominant in lakes and coastal
waters at times when diatoms and
other algae seasonally decline
Cryptomonads
Haptophytes
•Marine phytoplankton, few
freshwater, terrestrial
• Important in food webs
• Photosynthetic pigments
include Chlorophylls A and C,
fucoxanthin
• Some covered with calcium
carbonate plates.
- Coccolithophorids
haptonema
Haptophytes: coccolithophorids
Dinoflagellates
•Unicellular biflagellates
• Flagella reside in grooves: cingulum and sulcus
• Cellulosic cell walls in some
• Many produce toxic or bioluminescent compounds
Dinoflagellates
Toxic “red tide” dinoflagellate bloom
Dinoflagellate bioluminescence
Protection from predation?
Photosynthetic heterokonts
“Heterokonts”
Bacillariophyceae (diatoms)
Chrysophyceae ( golden algae)
Xanthophyceae (Yellow-green algae)
Phaeophyceae (brown algae, “seaweeds”)
“Heterokonts” (= Stramenopiles)
2 different types of flagella (smooth, hairy/tinsel)
(often only present during sexual reproduction, on “male” gametes)
Golden algae: Chrysophyceae
Mostly
unicellular or
colonial,
non-motile
Some
autotrophic,
others
heterotrophic
Synura: unicellular
chrysophyte with silica
scales
Dinobryon : colonial chrysophyte
Xanthophyceae: “yellow-green” algae
•Most non-motile,
filamentous
• Coenocytic: filaments
with multiple nuclei, not
separated by cell walls
Bacillariophyceae: Diatoms
Diatoms are Centric or Pennate
Centric: radial symmetry
bilateral symmetry
2-part cell wall (frustrule) composed of silicon dioxide (SiO2)
Ditylum (a centric diatom)
Ditylum (centric, girdle view)
Meiosis vs. Mitosis
Isogamy
Reproduction in Pennate Diatoms
is Isogamous
Iso = “sameness”
gamous = refers to gametes
Oogamy: centric diatoms
Navicula: pennate diatom
Assorted Diatoms
Assorted Diatoms
Assorted Diatoms
Assorted Diatoms
Assorted Diatoms
Macroalgae: Kelp (Phaeophyceae)
• Specialized functions in different parts of plant.
(but very little differentiation of cells or tissues)
Macroalgae: Kelp
Postelsia palmiformis: “sea palm”
• no gas bladders
• Thick, hollow stipe
Brown Alga Lifecycle