Green Algae - Fog.ccsf.edu

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Cyanobacteria
and
Algae
Prokaryotes and Eukaryotes
Prokaryotes
Eukaryotes
“primitive nucleus”
“true nucleus”
Lack clear nucleus and other
inclusions
Clear nucleus and other inclusions
All organisms with cells that lack a
nucleus
All organisms with cells that have a
nucleus
Nutritional Requirements of
Prokaryotes

Methods of obtaining carbon
Autotroph (“self-feeding)  incorporate carbon into
organic molecules from inorganic sources
 Heterotroph (“other feeding”)  derive carbon
from breakdown of organic compounds


Methods of deriving energy
Chemotroph (“chemical feeding”)  obtain energy
from catalyzing inorganic reactions
 Phototroph (“light feeding”)  obtain energy by
absorbing light photons

Symbiotic Relationships Between
Prokaryotes & Plants

Rhizobium lives in soil


Synthesizes enzyme nitrogenase which converts
unusable N2 to plant-available ammonium (NH4+)
Forms mutualistic relationship with legumes
within root nodules
Plant → carbohydrates & protection
 Bacterium → nitrogenase & other enzymes
 Both benefit from supply of fixed nitrogen

Cyanobacteria
“blue green algae”



Photosynthetic
chlorophyll a, phycobilins
fix nitrogen
Symbiotic Relationships Between
Prokaryotes & Plants

Other examples of symbiotic nitrogen fixing
Bacteria
Frankia – within cells of root nodules of alders
 Anabaena – association with water fern, Azolla
 Nostoc – invades cavities in gametophytes of
hornworts & cycads

Figure 17.11
Photosynthetic Protists
“Algae”
Algae = Photosynthetic Protists



Variety of life histories, body forms, ecological
roles
Often named for distinctive colors
Unicellular, colonial, multicellular
Phylum Chlorophyta
“green algae”





Unicellular, colonial, multicellular
Most found in freshwater, also some in shallow
marine habitats
Pigments: chlorophyll a & b, carotenoid
Food stored as starch
Cellulose cell walls
Green Algae
50 µm
(a)
(b)
(c)
Algal Reproduction

Zygotic



Gametic




diploid phase of life cycle is single-celled zygote
Examples: Volvox, green algae, Chlamydomonas
Multicellular sporophytes
haploid phase of life cycle is single-celled gamete
Examples: some brown algae like Cystoseira
Sporic


multicellular gametophytes & sporophytes
Examples: Ectocarpus, Ulva (isomorphic), Laminaria
(heteromorphic)
Zygotic l.h found commonly
in green algae
Gametic l.h. found in some
Brown algae, especially rockweeds
(Fucus, Pelvetia, Cystoseira)
Sporic l.h. found in kelps,
green algae, land plants
Zygotic Life Cycles
Chlamydomonas
Figure 18.
Ulothrix Life Cycle
Figure 18.
Spirogyra Sexual Reproduction
Phylum Chromophyta
(Stramenopiles)


All have 2 unequally sized flagella (hairy &
smooth)
Photosynthetic ones include:
Chrysophyceae (golden algae)
 Bacillariophyceae (diatoms)
 Phaeophyceae (brown algae)

Chrysophyceae
“golden algae”




Carotenoid pigments
Usually biflagellated
Most unicellular, some
colonial
Cell wall of cellulose
Figure 28.17
25 µm
Bacillariophyceae
“diatoms”



Unicellular algae with silica
tests (cell wall)
Important phytoplankton
Contain chl. a & c, fucoxanthin
Reproduction in Diatoms
Phaeophyceae
“brown algae”






abundant in cool, shallow marine
waters
Largest algae, multicellular thallus
Life history sporic or gametic
More Chlorophylls a & c,
fucoxanthin
Carbohydrates can move through
sieve elements & be stored
(“mannitol”)
Cell wall of cellulose & algin
Blade
Stipe
Holdfast
Gametic
(film)
Figure 18.
Sporic
Life Cycle
Phylum Rhodophyta
“red algae”
(b)
(c)

Widespread
Shallow to deep water
 Warm to cool water




.
Chlorophyl a, phycobilins
complex life cycle involving three types of
thallus structures (“triphasic life cycle”)
Cell wall of cellulose, agar or carrageenan
Triphasic
Life Cycle
Figure 18.
Phylum Euglenophyta
“euglena”




“mixotroph”, contains chlorophyll a & b
No cell wall
Contains eyespot
Lack cell wall
Phylum Dinophyta
“dinoflagellates”


Unicellular
Contain two flagella.
1 trails from the cell
 1 encircles the cell




disc-shaped chloroplasts with
xanthophyll pigments
Many with tiny projectiles
Many produce toxins (Red Tides)
Dinoflagellates
Ecological & Economic Importance

Phytoplankton



Help build tropical reefs



Base of aquatic food chains
Produce about 4x food as earth’s crops
Coralline green & red algae
Medicine, food, and fertilizer
Uses of algal cell walls




diatomite for filtering, bulking, abrasive
agar as culture medium, gel electrophoresis & in baking
carrageenan used as stabilizer
algin used to absorb water & as additive

Kelp movie
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