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Bio204 Lecture Midterm FC's


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What is the dictionary definition of algae?
-Traditional term for a series of unrelated groups of photosynthetic eukaryotic organisms lacking multicellular sex organs
What are some reasons as to why algae are important?
-71% of earth's surface is water
-50% of global primary production is algal
-Algae remove C02 from the atmosphere through photosynthesis:
6CO2 + 6H2O -> C6H12O6 +6O2
What was used as early evidence of the evolution of Cyanobacteria?
-one of the first forms of cyanobacteria like algae

Fossil records
-Cyanobacterium like fossils 3.5 billion years old!!!

Banded Iron Formations (BIFS)
-ferrous iron was very plentiful in ancient oceans
-it entered from hot cracks and fissures i the ocean's floor and from rives draining into the oceans
-3.5 billion years ago, the atmosphere and oceans contained very little oxygen
-Ferrous iron remained in solution in anoxic ancient seas and oceans
-once ocygenic photosynthesis started with the advent of Cyanobacteria, oxygenaccumulated in the atmosphere and in the surface waters of these ancient water bodies, reulting in the oxidation of ferrous iron to ferric iron
-ferric iron is insoluble, and precipitated to the bottom sediments on seasonal cycles, leaving bands of iron in the sediments
-over the period stretching from 3.5 to 2 billion years ago, the oceans became more and more oxygenated
-but much of this oxygen was precipitated with ferric iron
-20x more oxygen is now stored in BIFs than is presen in the atmosphere as a result of billions of years of oxygen production by photosynthesis and precipitation with iron
What structures are present on a Cyanobacteria cell?
-DNA fibrils
-thylakoid membrane
-cyanophycin granules
-cell wall
-gas vesicles
-plasmalemma (cell membrane)
-glycogen granules
-polyphosphate body
Discuss the Cyanobacteria thylakoid.
-evolved from invaginations of the plasmalemma
-usually located at the periphery of the protoplasm
-contans the photosynthetic pigments:
++chlorophyll a
****found in the thylakoid membrane
****are attaced to the outer surface of the thlatkoid membrane (peg like structure)
Discuss Cyanobacteria carotenoids.
-another set of accessory pigments, expands the useful light range
-located in the thylakoids, but also in the plasmalemma and cell wall
-fuctions to harvest energy from blue and green light, sequester free radicals of oxygen and as a UV sun block
Define Chromatic Adaptation
-some cyanobacteria can adjust pigment composition for changes in light quality

-redlight stimulates phycocyanin synthesis
-green light stimulates phycoerythrin synthesis
What are the main storage granules/bodies in cyanobacteria?
Glycogen granules:
-storage of glycogen between thylakoids

-storage of rebulose 1,5 biphosphate carboxylase/oxygenase (RuBisCo)

Cyanophycin granules:
-storage of nitrogen in proteins

Polyphosphate bodies:
-storage of phosphorus as polyphosphate
How do cyanobacteria move up and down the water column?
-By use of gas vacuoles
-low light, reduction of osmotically active solutes, gas vesicles reform and cell floats
-cell near surface, recieves lots of light, storage products increas, ion uptake, gas vesicles collapse, cell sinks

**Rise and falls to recieve light and to recieve nutrients as needed**
-specialized nitrogen fixing cells
-cyanobacteria are the only alge known to fix nitrogen
-a huge advantage when other forms of nitrogen are scarce
-atmospheric N2 -> N4 -> amino acids
-in order to fix N2, an oxygen free environment is necessary
-therefore, to avoid O2 production, heterocysts are photosynthetically inactive
-in addition, a thick cell wall is present to minimize O2 diffusion into the cell
-obtain energy through adjacent cells through cytoplasmic connections
-formation stimulated by low concentrations of ammonia and nitrate in the environment
-cytoplasmic connections between heterocysts and adjacent cells
-AKA resting spores
-occurs in Cyanobacteria
-akinete formation is triggered by unfavorbale conditions such as low light, nutrients, temp etc.
-develop from vegetative cells
-photosynthetic and repiratory activities can by reduced by 90%
-gas vacuoles disapper
-cytoplasmic density, ribosomes and cyanonphycin granules increase
-with loss of flotation and an increase in cell density, akinetes sink to the sediment
-with the return of favorable conditions, germination occurs
--cyanophycin and glycogen are metabolized
--gas vacuoles reappear, and cyanobacteria ascend into the water column

**akinete formation is a survival mechanism for re-populating environments
**akinetes are only produced by cyanobacteria that can also produce heterocysts
How do Cyanbacteria reproduce?
Asexual reproduction:
-binary fission
-cell enlargement, protoplast division into daughter cells (ENDOSPORES)
-budding cells from a large mother cell (EXOSPORES)
-filament fragments detach (HORMOGONIA)

Sexual Reproduction
-no sexual processes
-can transfer genes through conjugation, transformation or transduction
What is the relevance of Cyanobacteria to humans?
-eutrophication of freshwaters
-loss of water quality: taste and odour problems
-fish kills
-loss of recreational value
-food source (eg:spirulina was eaten by aztecs, rich in protein, considered a health food)
Why are Cyanobacteria dangerous?
-releases cyanotoxins
-releases hepatotoxins and neurotoxins
-contaminates livestock, fish, wildlife and humans
What are some basic characteristics to the phylum Rhodophyta?
-macroscopic multicellular algae, seaweeds
-few unicellular forms
-5000-6000 spp, <150 spp live in freshwater
-mainly marine
-abundant in warm waters
-high level of productivity
-can be found at >250 m depths
What structures are found on Rhodophyte Cell?
-chloroplast (2 membranes)
-golgi apparatus
-pyrenoid (formation of starch)
-starch (floridean)
Discuss the chloroplast and pigments of Rhodophyta
-pigments are similar to cyanobacteria
-phycoerythrin is more abundant than phycocyanin (thats why its red)
-has both chlorophyll 'd' and 'a'
Defin Chromatic adaptation.
-expands the range of useable light wavelengths for plants

eg:increased phycoerythrin content permits the existence of red algae at great depths (>200m) where only blue and green light are present
In Rhodophytes, what is a major component of the cell wall?
-cellulose (fibrillar fraction) embedded in an amorphous matrix (MUCILAGE)
What is Mucilage?
-an amorphous matrix found in the cell wall of Rhodophytes
-mucilage = polysaccharides,
-mucilage gives this algae its flexible, slippery feel
What is CARRAGEENAN? Might as well discuss Agar in this too.
-composed of the mucilage found on Rhodophytes
-important gelling and thickening agents in food, pharmaceuticals and paint industries
-obtained from irish moss and other types of red algae
-common to the class florideophyceae
-consists of a proteinaceous plug between 2 cells
-widespread among the red algae
-useful for taxonomic identification
-function is uncertain, thought to strengthen thallus
-found in the order Corallinales
-CaCO3 is deposited extracellularly in the cell wall
-defence mechanism against herbivores
-thrives in shallow turbulent tidal regions
-important for ref building
Define Symbioses
-a close asociation between organisms of 2 or more species
Define Endosymbiosis
-refers to one species living within another called the host
-explains the origin of the chloroplast in eukaryotic algae
-relevant to red and green algae

-heterotrophic cells acquired chloroplasts by incorporating cyanobacteria as endosymbionts
-normally the engulfed cell would be digested, but a mutualistic symbiotic relationship evolved
-inorganic nutrients (eg:N and P) and shelter were provided by the host
-organic nutrients (eg:sugars) were provided by the cyanobacterium
-as symbiont and host became more interdependant, they may have become a single organism
-therefore the chloroplast has 2 membranes; Outer = phagosome membrane (plasmalemma) of the host, Inner = plasmalemma of the endosymbiont
What evidence is used in suggesting the THEORY OF PRIMARY ENDOSYMBIOSIS is true?
-eukaryotic chloroplasts have common features with cyanobacteria (eg: circular DNA lacking histones)
-cyanobacteria occur as symbionts in the cells of many organisms (aid in nitrogen fixation)
What are some distinguishing features of the Phylum Chlorophyta?
-has chlorophylls 'a' and 'b', but NO phycobilisomes
-thylakoids are stacked in pairs
-chloroplast has double membrane
-no chloroplast endoplasmic reticulum
-starch is formed and stored in the chloroplast
-ranges from microscopic unicellular to multicellular macroscopic
-has flagella that occur in pairs or in multiples of 2
-isokont flagella
-no mastigonemes on the flagella
-majority found in freshwater
List the structures found in a chlorophyte cell.
-colony wall (if colonial)
-golgi apparatus
-cell wall
What are the cell walls of Chlorophyta composed of?
-mainly composed of cellulose
-xylans and mannans replace cellulose in the Caulerpales
-Volvocales have walls composed of glycoprotein
-Motile cells of the Micromonadophyceae, Charophyceae and Ulvophyceae often have scales
Discuss the Scales in the Chlorophyceae.
-became interlaced over evolutionary time
-coherent cell covering of scales developed into the THECA that covers many motile cells in the Chlorophyceae
-composed of crystalline, hydroxyproline rich glycoproteins associated with polysaccharides
-these coverings occur outside of the plasmalemma
Summarize the structures found in the Chlorophyceae chloroplast
-no phycobilisomes
-thylakoids occur in pairs (generally) and may be stacked into GRANA
-starch is now stored in the chloroplast
-ribosomes are scattered everywhere
What photosynthetic pigments are found in Chlorophyceae?
⬢Chlorophylls a and b (similar to higher plants)
⬢Main carotenoid is lutein (in chloroplast)
⬢Outside the chloroplast are other carotenoids (e.g., betacarotene),
may collect under nitrogen deficiency
⬢External carotenoids may impart a red or orange color
⬢But most cells appear green because chlorophyll a is not
as masked by accessory pigments as in other phyla
T/F Phycobilins are water insoluble
-phycobilins are water soluble
What is the Pyrenoid?
-found in the chloroplast
-a proteinaceous structure that contains RuBisCO and is involved in CO2 fixation via the Calvin cycle (production of carbon compounds
-movement of the whole organism toward (positive phototaxis) or
away from light (negative phototaxis)
What are Eyespots?
-important in phototaxis
-found in chloroplasts near the flagella
-common in motile cells
-consists of layers of lipid droplets in stroma
-colored orange red from carotenoids in lipid

-The eyespot reflects light back onto a photoreceptor
found in the plasma membrane above the eyespot.
⬢The photoreceptor consists of a chromophore (rhodopsin) and a protein
⬢Different amounts of light reflect back onto the photoreceptor while swimming
⬢The permeability of the plasma membrane to calcium is adjusted depending on the amount of light hitting the photoreceptor
⬢The concentration of calcium in the cytoplasm affects the beating rate of the flagella
⬢And the rate of beating changes the cells direction
-functions in osmoregulation
-found near the anterior end of the cell
-common in freshwater algae
-may also function in removing cellular waste
Discuss the flagella found in Chlorophyceae.
-usually occur in pairs
-if > a pair, then a primitive feature
-not common to all chlorophyta
-inserted anteriorly, but run along the cell wall
-are positioned in different locations depending on the taxonomic group
Where is the flagella positioned in Charophycean?
Where is the flagella positioned in Ulvophycean?
Where is the flagella positioned in Chlorophycean?
-note the theca
Where is the flagella positioned in Micromonadophyceae?
-its variable
What is an AXONEME?
-the cylindrical arrangement of microtubules
-9(x2) + 2 structure
What structures are present in the axoneme of the flagellum?
-outer microtubule doublet
-central microtubule
-dynein side arms
-radial spoke
-plasma membrane
How do flagella produce their 'whipping' motions?
-power strokes of the dynein arms, crawling on the back of adjacent microtubule filament causes movement
-ATP is the driving force for this motion
How is flagella used to propel Chalmydomonas and other anteriorly positioned flagellate organisms?
-flagella brought to sides, and whipping motions of the tip propel it forward

-if moving backwards, simply keeps flagella outstretched and wiggles like a worm
What is the structure of a BASAL BODY?
-lacks central microtubules
-outer microtubules occur as 9 triplets
-9(x3) + 0 structure
What is the functions of BASAL BODIES?
-anchors flagella
-similar to centrioles
--prior to cell division, the flagella are lost
--the 2 basal bodies remain and migrate to the nucleus, one at each pole where they are now called centrioles
--when cell divides, each daughter gets one centriole
--centriole replicates and moves to the periphery to assemble the new flagella of the daughter cells
How are organisms within Chlorophyta classified?
-based on ultra structure, biochemical, and molecular sequence

Ultrastructure investigation focus on conervative features: structures that reatin old characteristics like
-reproductive cells (zoids)
-flagella position and symmetry
-cell wall covers
-nuclear and cell division (cytokinesis)
What 4 conservative features will be compared to explain the current phylogeny in the chlorophyta?
1)Reproductive cells (zoids)
2)Flagella positiong and cell symmetry
3)Cell covering (cell wall?)
4)Nuclear and Cell division
What is the flagella position of Micromonadophyceae?
What is the flagella position of Chlorophyceae?
What is the flagella position of
What is the flagella position of Charophyceae?
subapical (lateral)
What is the cell symmetry of Micromonodaophyceae?
What is the cell symmetry of Chlorophyceae?
What is the cell symmetry of Ulvophyceae?
What is the cell symmetry of Charophyceae?
What is the motile cell cover of Micromonadophyceae?
What is the motile cell cover of Chlorophyceae?
What is the motile cell cover of Ulvophyceae?
What is the motile cell cover of Charophyceae?
-nuclear envelope remains through mitosis
-centrioles are external of the nuclear envelope

-nuclear envelope breaks down early in mitosis and reforms in telophase
-centrioles are in contact with microfilaments

-also in plants
-spindles remain present during cell division
How does cytokinesis occur in Micromonadophyceae and Ulvophycaea?
-infurrowing of the plasma membrane results in new cells
-most primitive method in the greens (similar to prokaryote division)
-spindle is PERSISTENT
-no microtubules involved outside of those in spindle
How does cytokinesis occur in Chlorophyceae?
-THECA may restrict division
-spindle COLLAPSES in telophase and daughter nuclei come close
-microtubules of PHYCOPLAST keep daughter nuclei separate and organize vexicles containing cell wall building materials
-phycoplast migrates from center to cell walls as cell plate is formed
-plasmodesmata may form during development of cell plate
-micotubules are in a parallel line of division
How does cytokinesis occur in Charophyceae?
-phragmoplast migrates from center to cell walls as cell plate is formed
-spindle is PERSISTENT
-plasmodesmata may form between daughter cells
What is Phragmoplast?
-double sets of microtubules PERPENDICULAR to the plane of division
Out of Micromonadophyceae, Chlorophyceae, Ulvophyceae and Charophyceae; which is the only one to have OPEN NUCLEAR DIVISION?
What is a Coleochatales?
-member of Charophyceae
-land plants are thought to have evolved from these
-most spp's are epiphytes that can be seen microscopically on macrophyte leaves in the shallow zone of lakes
-thallus is branched or discoid in shape
-1 cell thick
What features do Coleochaete and Embryophytes have in common?
1. Similar photosynthetic pigments, starch reserve and
well developed grana
2. Open (mitosis) and persistent spindles
3. Plant-like cell division by means of a phragmoplast
4. Asymmetric flagellated cells (lateral insertion of flagella)
5. Repeated loss of motility (flagella, centrioles) in both
6. Oogamous: large nonmotile egg cell is fertilized by a
smaller motile sperm
7. Zygote retained in parental thallus and is protected by vegetative cells
8. Zygote may receive nutrients from the enveloping haploid filaments (transfer cells)
9.Pattern of cell division is apical (localized growth
10. Pattern of cell dision in some Coleochaete is similar to that of parenchyma of higher plants
11. Molecular evidence (rRNA) shows that the Charophyceae are much more closely related to the land plants than to the rest of the Chlorophyta
-mass of cells produced by divisions in 3-D to form a tube, blade or cylinder
What 3 factors may influence cell morphology?
1) Predation (herbivory)
-eg: produce spines, mucilage, etc.

2) Resistance to sinking out of the water column
-eg: reduce size to avoid sinking

3) Algal surface to volume ratio
-eg:the bigger the ratio, the better
What are some defining characteristics of Caulerpa?
-marine alga occurring as seaweeds in marine coastal waters up to 100m deep
-cosmopolitan species
-consists of fronds attached to STOLONS (stems)
-RHIZOIDS (simplistic roots) extend down from the stonolon and attach to the rocks, sand,mud and other organisms
What is the problem with Caulerpa taxifolia?
-extremely invasive
-infested thousands of hectares of the Mediterranean Sea, displacing native spp's of seagrasses and becoming the dominant plant life
-within one year, it can kill and replace up to 50% of native seagrasses
-toxic to herbivores
-spreads through the aquarium industry, reproduces easily by fragmentaton, even small pieces will form new plants
-cause of biodiversity inclination
-huma activities such as tourism, fishing and recreation decline
How is Caulerpa taxifolia controlled?
-it is beyond control in the Mediterranean... too widespread
-natural predators are found in the tropics
-but outside of the tropics, there are few natural predators. Bring in exotic predators? That can be problematic too...
-natural predators are sea slugs
-can't simply tear Caulerpa out because fragmentation would give rise to more
-tried puttin a tarp over and injecting with CHLORINE
Caulerpa toxifolia is uninucleate.
-may grow meters in length, as a single cell
Approximately how many spp's of Euglenoids are there?
-800 to 1000 species
When did Euglenoids first appear in fossil record?
410-460 million years ago
How do Euglenoids move? Be vague.
-euglenoid motion (METABOLY)
Do all Euglenoids possess green-pigmented chloroplasts?
-only 1/3 possess it
-many of them are SAPROPHYTIC (absorb organic compounds for nutrition)
-many of them are PHAGOTROPHIC
-some are MIXOTROPHIC (capable of autotrophy and heterotrophy)
What are some distinguishing features of Euglenoids?
-Chloropylls 'a' and 'b'
-has carotenoids as accessory pigments
-thylakoids occur in stacks of 2 or 3
-chloroplast is surrounded by 3 membranes, 2 is from the chloroplast envelope, the other is the chloroplast endoplasmic reticulum
-storage product is paramylon (not starch), stored outside the chloroplast
-majority are nicellular organisms
-2 heterokont flagella
-no detected sexual reproduction
-many are heterotrophic organisms
-true cell wall is lacking (except in cysts)
-mastigonemes present on flagellum
What structures would you expect to see on a Euglenoid Cell Structure?
-axoneme (x-sec of flagellum)
-chloroplast ER
-contractile vacuole
-long flagellum
-paraflagellar swelling
-plasma membrane
-short flagellum
Describe the Euglenoid Long Flagellum in detail.
-contains a rod of amorphous material, called the PARAFLAGELLAR ROD
-AXONEME of 9(x2) + 2 configuration
-MASTIGONEMES spiral down the long flagellum in a single row
How does Euglenoid move?
Flagellar Propulsion
1)spiralling undulations of the long flagellum from the apex to base as the flagellum is bent back beside the cell = CELL GYRATION... Forward
2)the long flagellum is held out straight in front of the cell with just the tip mobile = SMOOTH GLIDING LOCOMATION, Backwards

-cells exhibit rapid shape changes
-cytoplasm accumaltes at one end of the cell and is then rapidly redistibuted, driving the cell forwards or backwards
-only possible when not using flagella
-like a sped up version of amoeboid movement
How is Euglenoid Metaboly possible?
-metaboly requires large changes in body shape, therefore body has to be flexible enough to accomodate these changes
-rapid shape changes are possible with sideways mothion of flexible pellicle strips
-pellicle strips are long ribbons that extend helically from either end of the cell(///)
-pellicle strips are 'S' shaped, therefor able to hook and hinge into an adjacent strip by microtubules
Describe the Euglenoid Pellicle in detail.
-found beneath the plasma membrane
-primarily proteinaceous (80% protein, 12% lipid)
-microtubules connect grooves and ridges
-not all pellicles are flexible
Describe the Euglenoid Lorica in detail.
-Lorica are found in the genus Trachelomonas
-Fe or Mn impregnated mucilage
-rigid cover over cell, not in contact with plasma membrane (loose)
-cells are photosynthetic (ie: has chloroplast)
-single plagellum protrudes through the apical pore, shorter flagellum remains within the cavity
-daughter cells leave by apical pore
Describe the Euglenoid RESERVOIR/CANAL/POCKET in detail.
-easily changes shape
-distorts as contractile vacuole discharges water into it
-reservoir is similar to the cytosome in protozoa of the Kinetoplastida
-Cytosome is used for phagotyophy in Kinetoplastida and some euglenoids
Describe the Eyespot, Paraflagellar Swelling and Phototaxis in relation to Euglena.
-in Euglenoids, the EYESPOT is in the sytoplasm, next to the RESERVOIR **in Chloropyta, the eyespot is in the chloroplast and the photoreceptor is in the plasma membrane**
-PHOTORECEPTOR is the PARAFLAGELLAR swelling next to the axoneme
-EYESPOT acts as a light shade
-presence or absence of light on the paraflagellar swelling is comunicated to the adjacent long flagellum
--if light is present, then in vertical position
--if light is absent, then in horizontal position
Describe the Euglenoid Chloroplast in detail.
-has chlorophylls 'a' and 'b'
-Beta carotene is the most prevalent carotenoid
-Chloroplasts are surrounded by 2 membranes of the chloroplast envelope plus one membrane of the chloroplast ER... therefore 3 membranes
-thylakoids are grouped into bands of 3, but only bands of 2 thylakoids extend into the pyrenoid
-outside the chloroplast in the cytoplasm, often adjacent to the pyrenoid, are PARAMYLON GRANULES
-GRANA are not present in euglenoids
-if Euglenoids are raised in the dark, they will lose their pigments. Mitochondria will increase for heterotrophic existence in this case
-Euglenoid chloroplast may have evolved from ingesting green alga (SECONDARY ENDOSYMBIOSIS)
What is the storage product found in Euglenoids?
-chemical structure resembles starch but has F'd up B-linkage and shit like that
How does Nuclear and Cell Division occur in Euglenoids?
-before mitosis the nucleus migrates forward to the reservoir
-basal bodies of flagella have already replicated
-2 basal bodies move to the poles of the spindle
-nuclear envelope remains intact (CLOSED MITOSIS)
-nucleolus also remains intact but greatly elongated in metaphse and dumbbell-shaped in telophase
-2 daughter nuclei separate by constriction of membrane
-During mitosis the reservoir expands and a new
set of flagella arise
-Pellicle strips are also duplicated
-Once mitosis is complete the cell cleaves longitudinally
from the anterior to posterior
-Division follows the helix of the pellicle
-Daughter cells are equal in size

**See slide 44 & 45, lec 5 for pics**
Describe the Euglenoid Cyst in detail
-cysts are formed under unfavorable conditions
-cells 'round-off' and secrete a thick sheath of mucilage
-can survive fo months
Describe the Bioremedial project that was discussed in class.
-there was tons of shit and contaminants in a water reservoir due to mining runoffs and shit.
-determined the best way to do this was to stimulate phytoplankton so that they can 'gently' remove the shit
-MESOCOSMS were used to simulate different aquatic environments being exposed to different phosphorous levels. Obviously used to find optimum concentration of phosphorous to encourage Algal Clamydomonas growth without further disrupting shit
⬢Phosphorus fertilizations resulted in algal growth
⬢P-fertilizations resulted in overall reduced surface water
contaminant concentrations
⬢Reduced surface water contaminant concentrations was a
result of sedimentation
⬢High P-load treatments resulted in increased contaminant
sedimentation rates
What are some basic characteristics to Dinoflagellates?
⬢Approximately 3000 known species
⬢Marine (90%), planktonic, biflagellate, unicellular organisms
⬢More abundant in warm marine waters
⬢Also bloom in summer in temperate waters
⬢The photosynthetic dinoflagellates are second only to diatoms
as primary producers in coastal waters
⬢Cause of red tides
⬢Cells can be autotrophic, or heterotrophic (50%), or
⬢Are involved in many important symbiotic relationships
⬢Are the champion swimmers of the flagellate algae
⬢Large cells (20 to 200 μm)
What are some distinguishing characteristics to Dinoflagellates?
⬢Chlorophylls a and c2
⬢Thylakoids occur in stacks of three
⬢Chloroplast is surrounded by two membranes of the
chloroplast envelope plus one membrane of chloroplast
endoplasmic reticulum (three membranes, unlike chlorophyta)
⬢Storage carbohydate: starch in cytoplasm
⬢Cellulose plates often make up a theca
⬢Two flagella that are dissimilar in structure (heterokont)
⬢Sexual reproduction present but uncommon
⬢No true cell wall
⬢Mesokaryotic nucleus
What structures would you expect to see on the External Surface of Dinophyta?
-epicone (epitheca)
-hypocone (hypotheca)
-longitudinal flagellum
-transverse flagellum
What internal structures would you expect to see in Dinophyta?
-chloroplast envelope
-chloroplast ER
-golgi apparatus
-trichocyst pore
-thecal plate
-plasma membrane
Describe the Dinoflagellate Theca in detail
⬢Thecal structure = outer plasma membrane and an inner single layer of vesicles **Do not confuse with Chlorophyte theca which is outside the plasma membrane**
⬢When thecal plates are present, dinoflagellate is considered ARMORED or THECATE
⬢Plates are made of cellulose and are locked together at edges
⬢Plates are formed in the golgi bodies and transported to the cell periphery in vesicles in which they remain
⬢Presence, absence and shape of plates is used to distinguish species
⬢When thecal plates are absent, the dinoflagellate is considered UNARMORED or NON-THECATE
Describe the Dinoflagellate Trichocysts in detail
⬢Ejectile rods that can be discharged from the cell
⬢Found at the periphery of most dinoflagellates
⬢Found attached to plasma membrane
⬢In armored species found in pores in thecal plates
⬢Formed in Golgi
⬢Consist of a rod-shaped crystalline core and a fibrous end
near the outer area
⬢Discharge under disturbance
(up to 200 μm) in milliseconds
⬢Purpose is obscure
Prey capturing device?
Describe the Dinoflagellate Flagella in detail
⬢Unlike Euglenophyta, two prominent flagella are present
⬢Both flagella attach at the junction of the girdle and the sulcus
⬢Both have the characteristic axoneme microtubule structure (9x2+2)
⬢Each flagellum arises from a separate flagellar canal
⬢In the cell, each flagellum ends in a basal body with the
characteristic 9 triplet microtubules
Longitudinal Flagellum
⬢Extends down the sulcus and beyond the cell when not contracted
⬢Fibrillar hairs (MASTIGONEMES) may cover entire flagellum
⬢Contains an R-fibre along length of flagellum that can contract, pulling flagellum into sulcus
⬢Longitudinal flagellum function: steering and propulsion by whipping-type action

Transverse Flagellum
⬢Typical, but coiled axoneme
⬢Striated strand composed of
centrin (contractile protein)
⬢A flagellar sheath encloses
axoneme and striated strand
⬢Single row of fibrillar hairs
⬢Lies in the girdle and is
helical in shape
⬢Attached to the girdle
except at the tip
⬢The axoneme is coiled like a left handed-screw
⬢Spiral waves are propagated along the axoneme (moves
like a ribbon)
⬢Downward thrust and rotation are created simultaneously
⬢The cell spins and moves forward
⬢Greek word dineo = to whirl
Describe Dinoflagellate locomotion.
-the axoneme of Transverse flagellum is coiled like a left handed screw
-spiral warves are proagated along the axoneme (moves like a ribbon)
-downward thrust and rotation are created simultaneously
-the cell spins and moves forward
-the fastest algae (200 to 500 um/sec)
-some undergo vertical migrations in the water column
Describe the Dinoflagellate chloroplasts in detail.
⬢As in the Euglenophyta:
1) Chloroplasts have two membranes of the chloroplast
envelope plus one membrane of chloroplast endoplasmic reticulum (CER)... therefore 3 membranes
2) Thylakoids are stacked into bands of three
⬢Pyrenoids may not be present
Describe the Dinoflagellate pigments in detail.
⬢Chlorophylls a and c2,
⬢Major carotenoid is PERIDININ
⬢Most Chlorophyll a and peridinin occur together in a water soluble protein complex called PCP (peridinin-chlorophyll aprotein)
⬢The PCP complex is very efficient at light capture and
energy transmission
Describe the Dinoflagellate nucleus in detail.
**Both euglenoid and dinoflagellate nuclei are unlike eukaryotic or prokaryotic nuclei.
**Considered intermediate or mesokaryotic
**In both euglenoids and dinoflagellates:
⬢Chromosomes are condensed and visible throughout mitosis
(prokaryotic) and interphase
⬢Chromosomes do not contain nucleohistone protein (unlike
other eukaryotes and similar to prokaryotes)
⬢Nuclear envelope remains intact during division
⬢Nucleolus persists and divides by pinching in two
⬢Chromosomes are attached to the nuclear envelope, not to
spindle microtubules
Describe the Dinoflagellate nuclear division process in detail.
⬢During prophase bundles of microtubules sink into the nucleus
⬢These occupy cytoplasmic channels through the nucleus (nuclear envelope remains intact)
⬢Each daughter chromosome attaches by a kinetochore to the nuclear envelope and to a microtubule (microtubules are in the cytoplasmic channel)
⬢Microtubules move in opposite directions and pull on the
kinetochores, this in turn, pulls on the pair of daughter chromosomes and separates them
⬢Nuclear envelope constricts and separates creating envelopes around daughter nuclei
**See slide 32, lec.6**
Describe the Dinoflagellate cell division process in detail.
⬢Asexual reproduction is most
common (binary cell division)
⬢Cell divides into two daughter cells along thecal sutures
⬢In Ceratium each daughter cell receives half of the thecal plates and one flagellum
⬢Daughter cells construct the
missing parts of armour
⬢However, in Peridinium all
armour is discarded and each
daughter cell rebuilds armour
**See slide 34, lec.6**
Describe the Dinoflagellate EYESPOT in detail.
⬢Less than 5% of dinoflagellates contain eyespots
⬢However, most exhibit phototaxis
⬢Certain heterotrophic dinoflagellates contain the
most complex eyespots of the algae
⬢These may be an adaptation
for a phagotrophic
existence (prey capture)
Discuss the symbiotic relationship between corals and dinoflagellates discussed in class.
•Zooxanthellae sp. are
photosynthetic dinoflagellates
that form symbiotic relationships with reef
forming corals (hard corals)
•Found in vesicles of host cells
•Zooxanthellae provide oxygen and organic substances (e.g, glycerol) to host
•Alga receives protection and inorganic nutrients (ammonium) from host
•Up to 80% of energy needs of hard corals may be met by the
•Hard corals develop only near the water surface, why?
-Corals consist of many
feeding polyps
•Calcification in hard corals is much more rapid when light is present….. when Zooxanthellae are photosynthesizing and producing glycerol for the coral
•When corals get “stressed” they lose their Zooxanthellae
•This results in the loss of color of many corals and is called CORAL BLEACHING
•This may occur from extreme temperatures, and/or a lack
of sunlight
•The corals may die, but often regain their symbiont within
a few months.
What causes Red Tides?
⬢Calm warm surface waters, low salinity and high nutrient
conditions favor bloom development
⬢These conditions often occur after heavy rain storms
⬢Red tides are visible at 10-20 million cells/litre
What are Red Tides?
⬢Reddish or brown hue of marine surface waters
⬢Usually caused by a bloom of dinoflagellates
⬢Color is caused by an accumulation of carotenoid pigments
⬢Generally restricted to autotrophic genera
⬢Common to tropical and and subtropical coast lines and
⬢About 40 species create serious toxins
⬢But can also be found in temperate coastal waters in late spring and summer
-Toxins may be produced
to deter herbivores
⬢Toxins from these blooms can be lethal: Saxitoxin is a neurotoxin leading to paralysis, Paralytic Shellfish poisoning (PSP), etc.
What is Pfiesteria piscicidia?
-a Dinoflagellate from hell...
⬢A non-pigmented dinoflagellate, a recent discovery
⬢Complex lifecycle (at least 20 different stages or forms)
⬢Kills fish and feeds on their remains
⬢Blooms in estuaries of southeastern U. S. (documented since 1991)
⬢Nutrient pollution (e.g. sewage, agriculture fertilizers) promotes
bloom formation as well as the
presence of certain fish
⬢Zoospore releases a neurotoxin (unknown) that creates lesions and kills fish
, then the zoospore consumes the dead fish flesh
⬢ A reverse food web dynamic: an alga kills a fish, and not
vice versa
⬢Note that the zoospore feeds
by extending its PEDUNCLE,
attaching to the red blood cell and sucking the cell contents out
What is a PEDUNCLE?
-a feeding structure found on Pfiesteria piscicidia
What are some human health implications of Pfiesteria piscicidia?
⬢In case of P. piscicidia, danger is not from consumption
of toxin containing seafood, but by contact of water
containing the toxin or inhalation of the toxin (as an
⬢Burning skin and eyes
⬢Blurred vision
⬢Acute respiratory difficulty
⬢Muscle cramping
⬢Nausea and vomiting
⬢Severe headaches and profound memory dysfunction
What are some basic characteristics to Diatoms?
•Approximately 10,000 to 12,000 known species
•Marine and freshwater
•Dominant phytoplankton of cold, upwelling nutrient
rich waters
•Indirectly support large fisheries
•Unicellular or colonial
•Account for 25% of global primary production
•Most are plankton, but some are benthic (bottom dwellers)
•In general, reproduction is asexual
•Live in “glass boxes” called FRUSTULES
•Frustules are not biodegradable and are found in geologic deposits
•Geologic deposits of diatoms are mined for use in water filters, abrasives (e.g., toothpaste), reflectants in highway paint, insulation,
and other uses
What are some distinguishing features of Diatoms?
⬢Chlorophylls a, c1 and c2
⬢Thylakoids occur in stacks of three
⬢Common Carotenoid pigment is FUCOXANTHIN (golden brown colored)
⬢Chloroplast is surrounded by two membranes of the chloroplast envelope plus two membrane of chloroplast endoplasmic reticulum... therefor 4 membranes
⬢Storage products: chrysolaminarin and lipid in cytoplasm
⬢Flagella are absent, except for male gametes of the Centrales order
⬢Have true cell walls: FRUSTULE
⬢Mitosis is open, spindle persistent
⬢Sporophyte dominant lifecycle
How have Diatoms evolved?
⬢May have evolved from unicellular flagellates
⬢Appear in the fossil record ~250 million years ago
⬢Centric forms were the first to appear 120 million years ago
⬢Pennate forms appeared 70 million years ago
⬢First freshwater diatoms were pennate forms which appeared
60 million years ago
⬢Assumed dominance in the plankton ~24 million years ago
Describe the Diatom Frustule in detail.
⬢Diatoms secrete an external cell wall composed of silica (SiO2) called the FRUSTULE
⬢This is a true cell wall, unlike the euglenoids and dinoflagellates
⬢Each frustule is composed of almost equal halves like a petrie dish
⬢Frustule is highly ornamented and used to distinguish species
-valves are connected to the girdle by a pectinaceous film
-the frustule is enveloped by an organic component or skin
What are the 4 basic patterns of ornamentation in Diatom Frustules?
-or radial, structure is arranged according to a central point

-structure is arranged
uniformly over the surface
without reference to a point or line

-structure is dominated
by angles

-structure is bilaterally

Note: Centric and Pennate diatoms form two major groups of diatoms
With regards to Diatoms, what are Raphes?
-found in Pennate diatoms
-a longitudinal slot in one or both valves
-cells with raphes can be motile
How do Diatoms move?
⬢Diatoms that have RAPHES can move along surfaces~ 0.25 to
25 μm per second
⬢Noticeable on rocks taken from stream beds (microscope
⬢Suspected to use motion to avoid nutrient limitation and shading
⬢How the cells move is still unclear
⬢Hypothesis: Raphe associated microtubules combine with
motor proteins as dynein to push cell along surfaces
-centric ones move super slow
How does Nuclear and Cell Division and Wall Formation occur in Diatoms?
-Unlike Euglenophyta and Dinophyta, cell division is somewhat typical in diatoms
-Exception: the formation of the silica cell wall
-Before division cell swells and forces valves apart:
-Mitosis is open (nuclear envelope breaks down)
-Centrioles are absent from spindle poles
-Microtubule organizing centers (MTOC) are
present at each pole (for assembling spindle microtubules)
-Spindle develops outside of nucleus and then enters via a breach in the nuclear envelope
-Nuclear envelope disappears (open mitosis), but spindle is
-Spindle is composed of two sets of overlapping half spindles
-Kinetochores of the chromosomes attach to microtubules and
chromosomes move along the microtubules of the half spindles towards the poles
-The two half spindles separate
-Cytoplasmic cleavage occurs by in growth of a furrow from the plasma membrane
-Nuclear envelopes then re-form around daughter nuclei, and nuclear division is complete
-Golgi bodies produce vesicles that collect beneath the plasma membrane
-These vesicles fuse to form the SILICALEMMA which expands to form the new valve (HYPOTHECA) in each daughter cell
-When the deposition of silica is complete the inside lining of the SILICALEMMA becomes the
-...Then additional golgi vesicles collect and fuse to form a silicalemma to form the GIRDLE between the EPITHECA VALVE and new HYPOTHECA VALVE in each daughter cell
-Eventually two daughter cells are formed
-Diatoms have an absolute requirement for silica
-Cell division will not take place without adequate supplies in the surrounding
-Silica uptake is a very energetic process
-Uptake occurs after cytokinesis, but before
cell separation (when silica is required to make new valves)
Note: Each daughter cell always synthesizes the hypotheca; the valve inherited from the parent always becomes the epitheca
⬢This results in a reduction in mean cell size with successive generations
⬢Eventually the cells become too small to survive.
⬢At ~ 30% of original diameter, sexual reproduction may occur and re-establish larger individuals in the population

**see slides 25, 27, 28, 29. Lec. 7 for pics**
Describe the Diatom Flagella in detail.
⬢Only the centric diatoms contain groups with flagellated sperm
⬢The sperm only have one flagellum with mastigonemes
⬢Axoneme is unusual: it lacks the two central microtubules (9x2 + 0)
⬢Basal bodies are unusual: consist of microtubule doublets not triplets
Describe the Diatom Chloroplast in detail.
⬢One or more pyrenoids are present in each chloroplast
⬢Thylakoids are grouped into bands of three
⬢However, in pyrenoid, thylakoids may occur in bands of two (like euglenoids)
⬢Chloroplasts are surrounded by 2 membranes of the
chloroplast envelope, and 2 membranes of the chloroplast
endoplasmic reticulum (CER)... Therefore 4 membranes of chloroplast
⬢The outer membrane of (CER) is continuous with the nuclear
envelope of the cell
⬢Storage product is chrysolaminarin (not a starch) and is found in the cytoplasm in vesicles (another beta-1,3-linked glucan like
Describe the Diatom Pigments in detail.
⬢Chlorophylls a and c1 and c2 are present
⬢Main carotenoid is fucoxanthin which gives the cells their golden-brown color
⬢All pigments lie in the chloroplast
Describe the Amnesiac Shellfish Poisoning problem discussed in lecture.
⬢Pseudo-nitzschia spp. can produce the neurotoxin domoic acid
⬢When shellfish consume this diatom they may concentrate the toxin in their tissues (shellfish are unaffected)
⬢When humans consume such
shellfish: memory loss, cramps, vomiting, disorientation, and death
may result.
⬢First case occurred in 1987 in P.E.I., resulting in three deaths and 153 illnesses across Canada
⬢Occurs when cells are deprived of nutrients (P and Si).
What are Paleolimnology Studies?
-the study of past conditions in freshwater lakes
-Diatom frustules can be extremely useful
-fossil remains of organisms in sedment provide a key to past lake conditions
-the cored sediments contain many algal fossils, particularly diatom frustules
⬢The sediment core is sliced into sections (e.g., 2.5 mm) from top to bottom.
⬢Under a microscope, diatoms fossils are identified in each section
⬢Each section is also dated (e.g., a section may represent a period that extends from 1,100 to 1,200 years before present)
⬢Thousands of diatom species exist with well documented
environmental preferences, e.g., for lake pH
⬢The presence, absence and abundance of diatom species in the sediment can be used to estimate past environmental conditions
What are some basic characteristics to Phaeophyta?
⬢Approximately 1500 species (low # compared to diatoms)
⬢Largest (e.g., up to 60 m in length) and most complex (no unicellular forms) members of the algae
⬢Almost all species are marine
⬢Dominate rocky coastlines of the northern hemisphere
⬢Some are annuals, but others may live up to 15 years
⬢Cell wall material of considerable economic importance
⬢Occupy same habitat as the Rhodophyta, but more northerly
⬢Exception: Some Sargassum spp. in the Sargasso Sea (North Atlantic Ocean)
What are some Distinguishing Features of Phaeophyta?
⬢Chlorophylls a, c1 and c2 (similar to diatoms)
⬢Thylakoids occur in stacks of three (similar to diatoms)
⬢Main carotenoid pigment is FUCOXANTHIN (similar to diatoms)
⬢Chloroplast is surrounded by two membranes of the chloroplast envelope plus two membrane of chloroplast endoplasmic reticulum (similar to diatoms)... Therefore 4 membranes
⬢No unicellular or colonial forms (unlike diatoms)
⬢Main storage product is LAMINARIN in cytoplasm
⬢Motile zoospores or gametes have two flagella inserted laterally
and mastigonemes present on one flagellum
⬢Stalked pyrenoid
⬢Cell wall of cellulose (structural part) and alginate (amorphous part)
Describe the evolution of Phaeophyta.
⬢Do not possess mineralized tissues (e.g., as the diatoms)
⬢First undisputed appearance occurred 7 to 15 million years ago
⬢Suspected of being much older
⬢From molecular sequences of ribosomal RNA, the brown algae
and diatoms diverged ~200 million years ago
What structures are present in a Hypothetical Brown Algal Cell?
-Chloroplast envelop
-chloroplast ER
-endoplasmic reticulum
-DNA fibrils
-nuclear envelope
-pyrenoid sac

**Note how nuclear envelope and pyrenoid sac are connected to the chloroplast envelopes**
What 3 components make up the Phaeophyta cell wall?
1) Cellulose is the structural component of the cell wall
(1-10% dry mass)

2) Alginate is found as an amorphous material of the intercellular matrix (up to 35% of dry mass)
⬢ Alginates provide flexibility upon the thallus, help prevent desiccation, play a role in ion exchange, and may inhibit colonization by other organisms

3) Sulfated polysaccharides known as fucans or fucoidans,
uncertain function

**Parenchymatous brown algae have plasmodesmata or pores in
cell wall. Protoplasm is continuous from one cell to another through the plasmodesmata**
What are some Industrial uses of cell walls of Phaeophyta?
⬢ Alginates are non-toxic and used extensively in industry
⬢ In food and pharmaceutical industries they are used as
stabilizers (e.g., ice cream where it prevents ice crystal
⬢ Also used in diet foods (swells in stomach)
⬢ >600,000 tonnes of Kelp are harvested annually for
Describe the Phaeophyta Chloroplast in detail.
⬢Pyrenoids are very common in the chloroplasts of brown algae
⬢Thylakoids are grouped into bands of three
⬢Chloroplasts are surrounded by two membranes of the
chloroplast envelope, and two membranes of the chloroplast
endoplasmic reticulum (CER).
⬢The outer membrane of (CER) is continuous with the nuclear
envelope of the cell
Describe the Phaeophyta Pigments in detail.
⬢Chlorophylls a and c1 and c2 are present
⬢Main carotenoid is fucoxanthin which gives the cells their
Brownish-yellow color
Describe the Pharophyta storage product in detail.
⬢Storage product is laminarin (not a starch) and is found in the cytoplasm (another beta-1,3-linked glucan like paramylon and chrysolaminarin)
Describe the Flagella of Phaeophyta.
-occurs on motile cells (zoospores or gametes)

Two Flagella:
1) Long anterior “TINSEL” flagellum with with two rows of mastigonemes
2) Shorter “WHIPLASH” posterior flagellum

**Flagella are inserted laterally

**Axoneme and basal bodies havetypical eukaryotic arrangement of microtubules
Describe the Phaeophyta EYESPOT in detail.
⬢Eyespot consists of 40-80 lipid globules between the outer most band of thylakoids and the chloroplast envelope
⬢Posterior flagellum usually has a swelling near its base which is a photoreceptor for phototaxis
⬢Eyespot acts as a concave
mirror focussing light
onto the flagellar swelling
Describe the Phaeophyta Nuclear and Cell Division processes
•Somewhat typical eukaryotic nuclear and cellular division
•Centrioles present and migrate to poles
•Nucleolus disappears during prophase (unlike Protista)
•During anaphase the nuclear envelope partially disintegrates:
“SEMI-CLOSED” mitosis
•Spindle collapses in telophase bringing the nuclei close together: “COLLAPSING SPINDLE” (Recall the green algae)
•Cell division is brought about by membrane furrowing or in some cases by cell plate formation
•Plasmodesmata are generated in either form of cell division (unlike the green algae)
What are some advanced features of Phaeophyta?
-growth and differentiation methods are reminiscent of higher plants
⬢Thalli in advanced brown algae may be composed of tissues analogous to those of land plants
⬢For example a holdfast, stipe and blade on west coast kelps (order: Laminariales)
⬢These are parenchymatous thalli, which develop by cell
division in various planes
(recall the Charophyceae)
⬢Cell division occurs at well
defined meristems (specific region where cells divide)
⬢Meristem location is used to classify brown algae
⬢Diffuse growth is common
to less advanced brown algae (cell division occurs throughout the thallus, growth is not localized)
-In some kelps there is an INTERCALARY MERISTEM between
stipe and blade that generates tissue in two directions,
increasing the length of the thallus
-In addition there is a surface meristematic region for increasing girth (meristoderm), analogous to the cambium of higher plants
-There may also be sieve tubes in the center of the stipe,
which are specialized cells that conduct food material, as
phloem cells in vascular plants
What is Primary Endosymbiosis?
⬢Heterotrophic cells, already possessing some organelles (e.g., nuclear envelope), acquired chloroplasts by incorporating Cyanobacteria as endosymbionts (mitochondria were derived by other symbionts)
⬢Normally the engulfed cell would be digested
⬢But, over geologic timescales, a mutualistic symbiotic relationship
⬢Inorganic nutrients (e.g., N and P) and shelter were provided by host
⬢Organic nutrients (e.g., sugars) provided by Cyanobacterium
⬢As symbiont and host became more interdependent, they may have become a single organism, i.e., inseparable

Two membranes envelope the chloroplast:
Outer = phagosome membrane (plasma membrane) of the
Inner = plasma membrane of the endosymbiont
What evidence is available that suggests the Theory of Primary Endosymbiosis is true?
1) Eukaryotic chloroplasts are similar to cyanobacteria:
-DNA in chloroplast are similar to cyanobacterial
DNA: circular and lacking histones
-Ribosomes in chloroplast are similar to cyanobacterial ribosomes: small 70S type unlike larger 80S type of eukaryotes
-Nucleotide sequences of DNA and ribosomal RNA are similar between chloroplasts and cyanobacteria

2) Cyanobacteria occur within the cells of many organisms
-In diatoms (for nitrogen fixation)
-In fungi (nitrogen fixation)
-In Glauocophyte algae
-In Cycads (land plants)
What is Secondary Endosymbiosis?
⬢This part of the serial theory of endosymbiosis attempts
to explain how all the other algae obtained chloroplasts
(e.g., Protista and Chromista)
⬢These ideas are more complex and often unresolved
⬢However, the ideas open our minds to the numerous
evolutionary paths that the algae have taken
i.e., land plant evolution is simple compared to the diverse
evolutionary path of the algae (remember 5 kingdoms
contain algae)
General Process (Over Evolutionary Time-Scales)
-A eukaryotic organism that had acquired a chloroplast via
primary endosymbiosis is itself taken up by a second
eukaryote to become a symbiont
-Recall that phagotrophy is the ingestion of particulate food
General evidence
⬢Many examples of endosymbiotic eukaryotic algae, e.g., the green alga Chlorella, is an endosymbiont of many dinoflagellates
⬢Diatoms and some green algae are also endosymbionts
of other eukaryotic algae
What is evidence is available to validify Secondary Endosymbiosis?
⬢First evidence came from the occurrence of more than two
envelopes around the chloroplasts of some algae
⬢Furthest membranes (e.g. one or two membranes of CER) is
thought to be remnant of the symbionts plasma membrane
or secondary hosts food vacuole
⬢Small nuclei and eukaryotic-sized ribosomes are found outside the
two inner chloroplast envelopes, but inside the chloroplast
endoplasmic reticulum (CER)
⬢These nuclei and ribosomes are eukaryotic, but unlike the hosts
How has Secondary Endosymbiosis occurred in Chromista?
Chromista: may have derived chloroplast from a red alga

Note: four membranes around chloroplast in Chromista
-Two innermost membranes are thought to represent
the chloroplast envelope of the endosymbionts

Outer two are CER:
-Inner one believed to be the plasma membrane of the symbiont
-Outer CER is thought to be the membrane of the hosts food vacuole which fused with nuclear envelope
How has Secondary Endosymbiosis occurred in Euglenoids?
Euglenoid chloroplasts are believed to be derived from a green algal symbiont

Note: three membranes surrounding the chloroplast in

-Two innermost membranes are thought to represent the chloroplast envelope of the endosymbionts chloroplast
-The outer most membrane is thought to represent the hosts
food vacuole
-What about the plasma membrane of the symbiont?
-Uncertain, perhaps it was lost or reduced over time
How has Secondary Endosymbiosis
occurred in Dinoflagellates?
-Dinoflagellate chloroplasts are believed to be derived
from many types of algal symbionts (e.g., diatoms)
-Most dinoflagellate chloroplast were derived by tertiary endosymbiosis
-Here, dinoflagellate chloroplasts arose by incorporation of
eukaryotic cells whose chloroplasts were themselves derived from secondary endosymbiosis (e.g., the diatoms)
-For example, molecular analysis has demonstrated that the chloroplast and accompanying nuclear material was derived from pennate diatoms

-Why not six membrane layers present in dinoflagellates?
-Uncertain, perhaps many were lost or reduced over time
What are some basic characteristics to the Phylum Xanthophyta?
⬢600 species
⬢Mainly freshwater, but some marine and terrestrial
⬢Most vegetative forms are non-motile
⬢However, small organisms compared to Phaeophyta
⬢Most zooids are flagellated
⬢Reproduction is mainly asexual (zoospores, aplanospores or vegetative)
Describe the Xanthophyta Chloroplast in detail.
⬢Chloroplast is surrounded by two membranes of the
chloroplast envelope plus two membrane of chloroplast
endoplasmic reticulum... therefore 4 membranes
⬢Outer membrane of chloroplast E.R. is continuous with outer
membrane of nucleus
What is the storage product of Xanthophyta?
-lipids and glucans
Describe the Xanthophyta Pigment in detail.
⬢Main pigment: chlorophyll a, small amounts of c1 and c2
⬢No fucoxanthin (unlike other Chromista)
⬢Thylakoids are banded in three
⬢Pyrenoids present (but not shown here)
⬢Most closely related to the Phaeophyta
What structures are in a Xanthophyte Zoospore?
-contractile vacuole
-flagellar swelling
-long flagellum
-short flagellum
Describe the Xanthophyta Flagella.
-occurs in zoospores
⬢Two flagella that are laterally inserted
(more anterior than brown algae):
1. Long flagellum (TINSEL) with mastigonemes
2. Short flagellum (WHIPLASH) with no mastigonemes
⬢Long flagellum can be 4-6x longer than the short flagellum
Describe the Xanthophyta Cell Wall
⬢Cell wall is mainly cellulose (sometimes contains silica)
⬢Cell wall often composed of two halves, like a petrie dish (a cap and a tubular basal portion)
⬢When growing the cap remains the same size, but the basal
portion elongates

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