ALGAL DIVERSITY
Chlorophyta (green algae) in Archaeplastida and from same distance ancestor Rhodophyta
(red algae) in Archaeplastida
Stramenopila: Bacillariophyta (diatoms) and Phaeophyta (brown algae) in Chromalveolata
Euglenophyta (Euglenozoans) in Excavate
Habitat: marine and freshwater as well as land
Growth form: unicellular, colony, unbranched filament, branched filament and
parenchymatic
Euglenozoa: Genus Euglena Stramenopila: Phaeophyta and Bacillariophyta
Archaeplastida (ancestor) to: Rhodophyta
Unicellular, microscopic organism/microscopic filaments, organism with macroscopic leaf-
like and stem-like structures (3D)
>7000 species mostly confined to sea water – Nori (Porphyra) in Japan for sushi
Coralline algae: cell walls impregnated with calcium and magnesium carbonate
Thallus produces gametes and fertilisation occurs on the thallus that grows into tiny diploid
things producing spores by mitosis born into shells producing conchocelis (filamentous)
Conchocelis helped with cultivating Porphyra
Red algae polysaccharides used to thicken ice cream (pink/red ice-cream pigment) –
Carrageenan’s (Gigartina)
Cell walls: cellulose, agar and carrageenan’s that store glycogen (floridean starch)
Sets group apart: gametes lack flagella and there are photosynthetic phycobilin pigments
(phycoerythrin and phycocyanin) as well as chlorophyll a and c
Phycobilin pigments give organisms red appearance as they absorb blue light that
penetrates deep into water. Red algae then photosynthesizes/flourishes at greater depths
than another algal group
Phycocyanin has a longer wavelength than Phycoerythrin (lower wavelength and small
amounts of carotene)
,Archaeplastida (ancestor) to: Chlorophyta which are Viridiplantae
Very diverse and ancestors of land plants as well as including land plants
Adaptations: developed complex multi-cellular bodies and some moved onto land therefore
ancestors of true plants
Habitat: most in fresh water, some in salt water, snow, shady or moist habitat as well as
being symbiotic with animals/fungi (lichens)
Green plant clades: Chlorophyta and Streptophyta
Land plants originated from Streptophyta algae and therefore includes land plants with 7
lineages – Charales (Chara) with 300 species and Coleochaetales with 30 species (both
multicellular freshwater algae)
Charales larger organisms than Coleochaetales. A shared ancestor of Charales and land
plants was complex freshwater alga
DNA: simpler unicellular organisms (Spirogyra) are closest to land plants
Growth form complexity
1 billion years at level of unicellular with algae complex multicellular forms a few times
Transition to life on land was complex so occurred a few times
Green algae remarkable developmental and metabolic pathway therefore survive major
disturbances and environmental changes
Multicellular bodies developed among red/brown algae by less tolerant of ecological change
Few red/brown algae survive in fresh water, soil, air or in animals compared to green algae
Living on land means no water challenge and plasticity necessary
Characters shared between green algae and higher plants:
Same type of chlorophyll a and b pigments, carotenoids, flagella lacking tubular hair,
chloroplast enclosed by double membrane, food storage in starch in chloroplast and
pyrenoids embedding in chloroplast (mosses)
Viridiplantae
Pigments: chlorophyll a and b and carotenoids
Carbohydrate storage: starch and cell wall: cellulose
Flagella: 2/4 no tinsel flagella
Habitat: freshwater
Growth forms: unicellular, colonial, filamentous, complex multicellular
,Unicellular green algae
Chlamydomonas represent primitive green algal growth forms
Microscopic, green, and rounded with 2 anterior flagella for movement
Each individual has eyespot helping direct swimming
Divide through mitosis asexually
Environment stimulates sexual cycle: availability of nitrogen and day length
Flagella of crossable lineages touch = entangled
Delicate cytoplasmic threads develop between cells
Cell walls dissolve and cytoplasm of 2 cells merges
Fertilisation occurs when nuclei of 2 cells fuse = single large diploid nucleus
Diploid zygote surrounded by thick/prickly walls for protection against heat and desiccation
After rest phase, zygote divides through meiosis = 4 haploid zoospores (2 each mating type)
Retract flagella and settle down as immobile dormant uniceullar orgnaims when
environment dries out and when water is avaible new flagella form so the cells become
enlarged and speices reproduces immediately
Major lineage = formation of colonies: Volvox with 500-60 000 Chlamydomonas-like
individuals arranged in hollow space
Colony forming green algae are motile/non-motile
Colony moves forward through synchronised motion of flagella of all members
Individual cells enlarge inward and bud off into centre of sphere during vegetative
reproduction (asexual)
Daughter colonies formed in parental colony & released when parental colony disintegrates
Sexual reproduction oogamous, enlarged cells give rise to daughter colonies changing into
fertile egg cells, packets of sperm formed elsewhere in same/different colony, zygote forms
after fertilisation enters rest phase in parental colony, when dormancy broken zygote
undergoes meiosis = 4 zoospores and spores divide mitotically to give rise to new colonies
Main points
1. 6 protist groups with Euglenoids animals/plant-like and Stramenopila oxygen-wise
2. Red algae no motile flagella, unique pigments and evolved structurally (not habitat)
3. Green algae plasticity allowed for transition to land sharing traits with land plants
, Filamentous green algae
Microscopic, branched, and unbranched
Epiphytic, attached to rocks or free-floating
Meiosis being zygotic or sporic (gametic meiosis uncommon)
Asexual reproduction by fragmentation
Sexual reproduction by conjugation
2 cells of neighbouring filaments grow towards each other
Outgrowths merge to form connecting tube
Content of 1 cell moves through tube to second cell
Diploid nucleus = meiosis and 3 haploid cells disintegrate and 1 divide = new filament
Multicellular green algae: Chara
Chara most complex, plant like green algae comprised of dichotomously branched filaments
with leaf-like structures at nodes
Cells of nodes, internodes and leaf-like structures develop from 1 apical cell
Wrongly views as aquatic vascular plant because of vegetative morphology and size
Reproductive structures differ from typical higher plant structures but unique among algae
– all included cells are fertile
Antheridia and oogonia are multicellular and surrounded by sterile cell layer
Outer layer sterile cells unusual for algae but Chara shares it will higher plants as well as
produces flavonoids (only algal group like land plants)
Ecological role of algae
1. Wide range of habitats: fresh/sea water or moist soils, rooftops, walls, and trees
2. Mutualism: unicellular species endosymbionts in diverse sea organism and green
algae live symbiotically with fungi to form lichens
3. Primary production: algae maintain aquatic ecosystems, constitute plankton (base
of food chain) with unicellular organisms, diatoms/microscopic algae in plankton fix
1/2 – 2/3 of photosynthetic carbon and algal photosynthesis oxygenates all waters
4. Habitat creation: brown/red algae form forests in tidal zones (habitats for others),
coral reefs are diverse and productive communities providing
food/shelter/protecting shores from erosion, reef corals primary producers in reef
communities through symbiosis with unicellular algae
Coral colony has polyps that are heterotrophic and feed on small particles/animals floating
in water and photosynthetic endo-symbiotic algae provide a source of nutrition to corals
Reefs formed by calcium carbonate produced by tiny coral polyps (main builder of reefs)
Coralline large cement corals together with calcium and tube works/molluscs donate hard
skeletons
Chlorophyta (green algae) in Archaeplastida and from same distance ancestor Rhodophyta
(red algae) in Archaeplastida
Stramenopila: Bacillariophyta (diatoms) and Phaeophyta (brown algae) in Chromalveolata
Euglenophyta (Euglenozoans) in Excavate
Habitat: marine and freshwater as well as land
Growth form: unicellular, colony, unbranched filament, branched filament and
parenchymatic
Euglenozoa: Genus Euglena Stramenopila: Phaeophyta and Bacillariophyta
Archaeplastida (ancestor) to: Rhodophyta
Unicellular, microscopic organism/microscopic filaments, organism with macroscopic leaf-
like and stem-like structures (3D)
>7000 species mostly confined to sea water – Nori (Porphyra) in Japan for sushi
Coralline algae: cell walls impregnated with calcium and magnesium carbonate
Thallus produces gametes and fertilisation occurs on the thallus that grows into tiny diploid
things producing spores by mitosis born into shells producing conchocelis (filamentous)
Conchocelis helped with cultivating Porphyra
Red algae polysaccharides used to thicken ice cream (pink/red ice-cream pigment) –
Carrageenan’s (Gigartina)
Cell walls: cellulose, agar and carrageenan’s that store glycogen (floridean starch)
Sets group apart: gametes lack flagella and there are photosynthetic phycobilin pigments
(phycoerythrin and phycocyanin) as well as chlorophyll a and c
Phycobilin pigments give organisms red appearance as they absorb blue light that
penetrates deep into water. Red algae then photosynthesizes/flourishes at greater depths
than another algal group
Phycocyanin has a longer wavelength than Phycoerythrin (lower wavelength and small
amounts of carotene)
,Archaeplastida (ancestor) to: Chlorophyta which are Viridiplantae
Very diverse and ancestors of land plants as well as including land plants
Adaptations: developed complex multi-cellular bodies and some moved onto land therefore
ancestors of true plants
Habitat: most in fresh water, some in salt water, snow, shady or moist habitat as well as
being symbiotic with animals/fungi (lichens)
Green plant clades: Chlorophyta and Streptophyta
Land plants originated from Streptophyta algae and therefore includes land plants with 7
lineages – Charales (Chara) with 300 species and Coleochaetales with 30 species (both
multicellular freshwater algae)
Charales larger organisms than Coleochaetales. A shared ancestor of Charales and land
plants was complex freshwater alga
DNA: simpler unicellular organisms (Spirogyra) are closest to land plants
Growth form complexity
1 billion years at level of unicellular with algae complex multicellular forms a few times
Transition to life on land was complex so occurred a few times
Green algae remarkable developmental and metabolic pathway therefore survive major
disturbances and environmental changes
Multicellular bodies developed among red/brown algae by less tolerant of ecological change
Few red/brown algae survive in fresh water, soil, air or in animals compared to green algae
Living on land means no water challenge and plasticity necessary
Characters shared between green algae and higher plants:
Same type of chlorophyll a and b pigments, carotenoids, flagella lacking tubular hair,
chloroplast enclosed by double membrane, food storage in starch in chloroplast and
pyrenoids embedding in chloroplast (mosses)
Viridiplantae
Pigments: chlorophyll a and b and carotenoids
Carbohydrate storage: starch and cell wall: cellulose
Flagella: 2/4 no tinsel flagella
Habitat: freshwater
Growth forms: unicellular, colonial, filamentous, complex multicellular
,Unicellular green algae
Chlamydomonas represent primitive green algal growth forms
Microscopic, green, and rounded with 2 anterior flagella for movement
Each individual has eyespot helping direct swimming
Divide through mitosis asexually
Environment stimulates sexual cycle: availability of nitrogen and day length
Flagella of crossable lineages touch = entangled
Delicate cytoplasmic threads develop between cells
Cell walls dissolve and cytoplasm of 2 cells merges
Fertilisation occurs when nuclei of 2 cells fuse = single large diploid nucleus
Diploid zygote surrounded by thick/prickly walls for protection against heat and desiccation
After rest phase, zygote divides through meiosis = 4 haploid zoospores (2 each mating type)
Retract flagella and settle down as immobile dormant uniceullar orgnaims when
environment dries out and when water is avaible new flagella form so the cells become
enlarged and speices reproduces immediately
Major lineage = formation of colonies: Volvox with 500-60 000 Chlamydomonas-like
individuals arranged in hollow space
Colony forming green algae are motile/non-motile
Colony moves forward through synchronised motion of flagella of all members
Individual cells enlarge inward and bud off into centre of sphere during vegetative
reproduction (asexual)
Daughter colonies formed in parental colony & released when parental colony disintegrates
Sexual reproduction oogamous, enlarged cells give rise to daughter colonies changing into
fertile egg cells, packets of sperm formed elsewhere in same/different colony, zygote forms
after fertilisation enters rest phase in parental colony, when dormancy broken zygote
undergoes meiosis = 4 zoospores and spores divide mitotically to give rise to new colonies
Main points
1. 6 protist groups with Euglenoids animals/plant-like and Stramenopila oxygen-wise
2. Red algae no motile flagella, unique pigments and evolved structurally (not habitat)
3. Green algae plasticity allowed for transition to land sharing traits with land plants
, Filamentous green algae
Microscopic, branched, and unbranched
Epiphytic, attached to rocks or free-floating
Meiosis being zygotic or sporic (gametic meiosis uncommon)
Asexual reproduction by fragmentation
Sexual reproduction by conjugation
2 cells of neighbouring filaments grow towards each other
Outgrowths merge to form connecting tube
Content of 1 cell moves through tube to second cell
Diploid nucleus = meiosis and 3 haploid cells disintegrate and 1 divide = new filament
Multicellular green algae: Chara
Chara most complex, plant like green algae comprised of dichotomously branched filaments
with leaf-like structures at nodes
Cells of nodes, internodes and leaf-like structures develop from 1 apical cell
Wrongly views as aquatic vascular plant because of vegetative morphology and size
Reproductive structures differ from typical higher plant structures but unique among algae
– all included cells are fertile
Antheridia and oogonia are multicellular and surrounded by sterile cell layer
Outer layer sterile cells unusual for algae but Chara shares it will higher plants as well as
produces flavonoids (only algal group like land plants)
Ecological role of algae
1. Wide range of habitats: fresh/sea water or moist soils, rooftops, walls, and trees
2. Mutualism: unicellular species endosymbionts in diverse sea organism and green
algae live symbiotically with fungi to form lichens
3. Primary production: algae maintain aquatic ecosystems, constitute plankton (base
of food chain) with unicellular organisms, diatoms/microscopic algae in plankton fix
1/2 – 2/3 of photosynthetic carbon and algal photosynthesis oxygenates all waters
4. Habitat creation: brown/red algae form forests in tidal zones (habitats for others),
coral reefs are diverse and productive communities providing
food/shelter/protecting shores from erosion, reef corals primary producers in reef
communities through symbiosis with unicellular algae
Coral colony has polyps that are heterotrophic and feed on small particles/animals floating
in water and photosynthetic endo-symbiotic algae provide a source of nutrition to corals
Reefs formed by calcium carbonate produced by tiny coral polyps (main builder of reefs)
Coralline large cement corals together with calcium and tube works/molluscs donate hard
skeletons
