E. Special adaptations
1. flagellae
2. gas vacuoles - can adjust
their buoyancy, position in the water column
3. mixotrophy
4. many can survive
desiccation
for years or have resting stages that can do so
II. Taxonomic survey
A. Cyanophyta (cyanobacteria; blue-green
algae)
1. Ancient group --
stromatolites
-- fossils that are 3 by old
2. Distinguishing
characteristics
a. They are prokaryotic --
b. pigments
1) chlorophyll a
2) secondary pigments - phycobilins
a) phycoerythrin - red (marine red tides)
b) phycocyanin - blue -- gives the blue-green color
c. storage product - glycogen-like substances
d. cell wall - mucopolysaccharide with unique amino acids
e. no flagella
3. Some are nitrogen fixers
a. use the enzyme nitrogenase
b. some have heterocysts, specialized thick-walled cells in
which
N2 fixation occurs
4. Have another type of
specialized cell - akinete - dormant cell
5. Some are toxic -- kill
cattle, dogs
a. Examples:
b.
Toxins hepatotoxins, neurotoxins
6. Common genera
a. Oscillatoria – (Planktothrix)
filaments with short vegetative cells;
no heterocysts; an indicator of beginning eutrophication;
tolerant of low light
b. Lyngbia
c. Anabaena - heterocysts and akinetes
d. Chroococcus
e. Microcystis -- commonly in high abundance in
eutrophic
lakes and can reach nuisance bloom proportions;
some species and strains produce
toxins
f. Aphanizomenon - parallel filaments in bundles; N fixer
g. Spirulina -- common in health food stores as a high
protein
food; grows in saline ponds; eaten by flamingoes
h. Gleotrichia - often occur as 'puff ball' colonies with
heterocysts
on the inside
i. Nostoc
The rest of the divisions are eukaryotic
B. Chlorophyta (green algae)
1. Distinguishing
characteristics
a. eukaryotic
b. pigments
1) chlorophyll a
2) chlorophyll b
c. storage product - starch
d. cell wall - cellulose
e. may have flagella (0-8)
2. Pigments and storage
products lead many scientists to believe that some ancient members of
the
chlorophyta
were the ancestors of higher plants
3. Common genera
a. Spirogyra - spiral chloroplast
b. Pediastrum; Hydrodictyon - autocolony formation –
each
cell forms a whole new colony
c. Chlamydomonas/Gonium/Pandorina/Volvox-
(order Volvocales) from a single cell with 2 equal length flagella
to multicellular forms with colonies of different sizes
d. Closterium (desmid -- 2 half cells with mirror images) also Staurastrum
and Microasterias, Cosmarium
desmids are common in low pH waters
e. Scenedesmus
C. Cryptophyta (cryptomonads)
1. Distinguishing
characteristics
a. eukaryotic
b. pigments
1) chlorophylls a and c
2) many secondary pigments; carotenes and unique xanthophylls -- can be
different colors from green, blue, brown, olive, red
c. storage - starch
d. no cell walls - naked
e. biflagellate
2. Unicellular
3. Are generally small and
good/preferred food for zooplankton
4. Common genera
a. Cryptomonas - capable of mixotrophy -- will ingest
bacteria
D. Chrysophyta (golden algae; yellow-green
algae; diatoms)
1. Distinguishing
characteristics
a. eukaryotic
b. pigments
1) chlorophylls a and c
2) carotenoids (e.g., b-carotene);
fucoxanthin
c. storage product - chrysolaminarin (beta 1-5 glucan); oils
d. cell wall
1) naked
2) cellulose
3) silica frustule (diatoms)
e. may or may not have flagella - 1 or 2 if present
2. Groups
a. Class Chrysophyceae (Golden Algae)
1) Ochromonas – single celled
2) Synura - cluster of cells, each with 2 flagellae; golden
brown
color; no division of labor between cells
3) Mallomonas - has silica plates, each with a spicule;
these
spicules increase the effective size of the cell
and make it harder for some zooplankton to ingest it
4) Dinobryon - makes a lorica out of cellulose;
has
a diploid zygote that is a resting stage
(can survive for years in the sediments)
b. Class Bacillariophyceae (Diatoms)
1) Have frustules made of silica with 2 valves -- fit together
with
2 intercalary bands
valve view; girdle view; epitheca and hypotheca
2) Unicellular or colonial
3) Diatomaceous earth – diatom frustules in sediments
4) Opal is the mineralized form of diatoms in sediments
5) Reproduction:
a) the two valves subdivide
b) each always makes a hypotheca
c) progressive decrease in size
d) sexual reproduction occurs and restores the original size --
zygote known as an auxospore
6) Orders
a) Centrales -- radially symmetrical in valve view(mostly
marine
and pelagic)
i. Aulacosira (Melosira) - colonial
ii. Stephanodiscus
iii. Cyclotella
b) Pennales - bilaterally symmetrical (mostly freshwater); some
groups have a raphe (split in frustule)
through which organic material is released that allows them some
'gliding'
motility on surfaces --
'pennate diatoms'
i. Synedra
ii. Fragillaria
iii. Asterionella - never seen auxospores or gametes,
but
assume that they occur because the cells undergo
the same size decrease and then increase
iv. Tabellaria
v. Navicula - has a raphe
vi. Cocconeis - often found on rocks in streams
E. Pyrrophyta (dinoflagellates)
1. Distinguishing
characteristics
a. eukaryotic
b. pigments
1) chlorophylls a and c
2) xanthophylls
c. storage product - starch
d. cell wall -- cellulose; some may be armored theca
e. flagella -- typically biflagellate in equatorial and longitudinal
grooves
2. Common
a. Ceratium - armored dinoflagellate; covered with
cellulose
plates
b. Peridinium
c. Gymnodinium - non-loricate (related to endosymbionts in
corals)
3. Interesting facts
a. red tides
b. Pfisteria outbreaks (non-photosynthetic dinoflagellate)
c. Biolumninescence -- Noctoluca
d. Some may have extremely complicated lifecycles with amoeboid,
predatory
or parasitic stages --
active area of controversy and research
F. Euglenophyta
1. Distinguishing
characteristics
a. eukaryotic
b. pigments
1) chlorophylls a and b
2) carotenoids
c. storage product – paramylon (polymer of glucose)
d. cell wall – typically no cell walls; have pellicles (strips
of
protein) within the cell membrane
e. flagella – typically 2, often with hairs
2. Common
a. Euglena
b. Phacus
3. Interesting facts
a. Can take up dissolved organic molecules from the water
b. Have an eyespot
G. Rhodophyta
1. Distinguishing
characteristics
a. eukaryotic
b. pigments
1) chlorophylls a and d
2) phycobilins, especially phycoerythrin
c. storage product – starch
d. cell wall – cellulose
e. no flagellated cells
2. Common – found mostly
in well oxygenated cold streams
a. Audouinella (Rhodochorton) – small, tufted
b. Batrachospermum – ‘frog eggs’
3. Interesting facts
a. Mostly marine
b. Marine species are often used as food emulsifiers (agar, carageenan)