midterm 2 - to study Flashcards
the ecological importance of dinoflagellates
- marine primary production
- symbionts in coral reefs
- harmful algal blooms (HABs) including red tide
- bioluminescence –> impacts predator prey interactions
Based on cell covering characteristics, what is the difference between a thecate (or armoured) and athecate (or unarmoured) dinoflagellate?
thecate (armoured) dinoflagellate =
have cellulose thecal plates within alveoli
- top = epitheca
- bottom = hypothecated
athecate (or unarmored) =
lack cellulose thecal plates, more flexible
** alveoli (membrane sacs - under cell membrane) always there, but sometimes filled with cellulose and sometimes not (empty)
What are thecal plates made of?
cellulose
located within alveoli, UNDER the plasma membrane
What are the morphological differences between a desmokont and a dinokont cell?
Desmokont =
- 2 large plates (valves)
- dissimilar flagella emerge at cell apex
Dinokont =
- divided into 2 parts –> epitheca and hypothecated
- flagella emerge from separate grooves (cingulum and sulcus)
- more common
Describe the pusule and its function
an unusual membrane-bound organelle thats connected to the exterior (near flagella)
involved in excretion, osmoregulation, and fluid balance
Describe motility in dinokont dinoflagellates
two flagella
one transverse and one longitudinal
Transverse =
in cingulum, 50% forward swimming speed and rotation
–> forward motion and rotation
Longitudinal =
in sulcus, 50% swimming speed and steering
–> aids in steering
very good swimmers –> winners at the end of the season
Trichocyst
= ejectable rod like protein structures used for defence
defensive projectiles
protein rods
almost all dinos
explosive release when disturbed
Scintillon
organelles containing luciferase and luciferin for bioluminescence
Peridinin
a unique xanthophyll pigment aiding in photosynthesis
Sulcus
longitudinal groove where longitudinal flagellum is located
Cingulum
transverse groove where transverse flagellum is located
Alveoli
membrane sacs (flattened vesicles) beneath the plasma membrane that can hold cellulose for thecal plates in armoured dinos
Amphiesmal
the combination of alveolar vesicles and membranes
zooxanthellae
symbiotic dinoflagellates living in corals
Planozygote
flagellated motile zygote formed after gamete fusion
Hypnozygote
non-motile (unflagellated)
thick-walled dormant cyst for survival
How is bioluminescence produced in dinoflagellates?
Luciferase oxidizes luciferin, producing a flash of blue light
Draw the life cycle of a typical dinoflagellate.
**Drawing on iPad
**Drawing on iPad
Briefly explain the role of cyst formation in the survival and dispersal of dinoflagellates.
cysts enable survival in adverse conditions (low nutrients, temperature changes)
serve as a dispersal mechanism in sediments
Why do dinoflagellates outcompete other phytoplankton in well-stratified
waters at the end of the growing season in marine temperate zones?
dinoflagellates can swim very well in comparison to other phytoplankton
1) efficient swimming to access light and nutrition
2) do better end of season when everything is calmer –> vulnerable to turbulence
3) ability to store nutrients and regulate buoyancy
4) mixotrophy
diatoms
How do you define a photosynthetic stramenopile?
heterokont (different flagella) alga with chlorophyll a, chlorophyll c, fucoxanthin, and a silica cell wall
Why are diatoms so important in the ecology and biogeochemistry of the oceans?
contribute ~20% of global carbon fixation
~40% of oceans primary production
key players in silica cycle and biogenic sedimentation
- link biogeochemical cycles of Si, N, and C
In which environments do planktonic diatoms flourish?
cold, nutrient rich waters
(upwelling zones, high-lattitude seas)
describe 2 main diatom forms
- pennate
- bilaterally symmetric, often benthic
- raphe system for gliding and motility - centric
- radially symmetric, often planktonic
Describe the different parts of the cell wall in diatoms
Frustule (theca)–> protoplast enclosed
Epitheca (large upper valve)
Hypotheca (small lower valve)
Raphe
- slit for movement in some pennate diatoms
Aerolae
- pores that penetrate frustule
- for movement of gasses, nutrients etc
Rimoportulae or labiate (lipped) processes
- polysaccharide excretion
Fultoportulae or central strutted processes
- secretion of chitin fibrils
advantages of cell wall in diatoms
1) protection from grazing
2) structural integrity
3) resistance to enzymatic attack
what is the frustule made of ?
silicon dioxide (SiO2)
can diatoms produce toxic blooms ?
yes
describe asexual reproduction in diatoms
each daughter cell inherits one half of the parent frustule and synthesizes a new smaller half
Parental frustule retained as epitheca of daughter cells (frustule lid) and new hytoptheca produced by daughter cells (frustule bottom)
Explain with a labeled diagram the typical reduction in cell size that diatoms experience over several generations of mitotic cell division.
**Drawing on iPad
Over successive divisions, diatom cells decrease in size until they undergo sexual reproduction.
Describe with a labeled diagram the life cycle of a
(i) centric and
(ii) pennate diatom.
In each case, indicate the type of life cycle.
** Drawing on iPad
** drawing on iPad
i) centric =
Oogamous sexual reproduction, gametic meiosis
ii) pennate =
Isogamous sexual reproduction
What is the effect of sexual reproduction on diatom cell size?
restores cells to maximum size via auxospore formation
how do benthic pennate diatoms move ?
use the raphe system to secrete mucilage for gliding and attachment
“jerky”
Describe the different ways in which planktonic diatoms can retard sinking.
1) oil droplets for buoyancy
2) chain formation to increase drag
3) spines and projections to reduce sinking speed
can diatom spores develop under low Si availability ?
no, silica is required for frustule development
raphe
slit in centre of pennate diatoms, for movement across substrates with mucilage gliding
areolae
pores in frustule which allow for movement of gasses and nutrients etc
rimoportulae
tubular pores for polysaccharide excretion
fultoportulae
involved in buoyancy control
secretion of chitin fibriles
silica deposition vesicle
organelle for frustule synthesis
resting cell
dormant stage for survival
what is the distinctive accessory pigment and storage compound in diatoms
fucoxanthin
crysolaminaran
Under what environmental conditions do diatoms typically switch to heterotrophic nutrition?
low light conditions and high dissolved organics
Where are biogenic siliceous sediments most common in the oceans?
upwelling zones
polar regions
deep-sea basins
what does the term “silicate ocean” refer to ?
regions where diatoms dominate over carbonate-secreting phytoplankton
guest lecture
Explain how phytoplankton (e.g.diatoms) interact with and control biogeochemical cycles (e.g. silicon cycle)?
1.Diatoms and Biogeochemical Cycles
- dominate silicon (Si) cycling in marine ecosystems.
- Diatom photosynthesis contributes ~20% of global primary production, comparable to terrestrial rainforests.
- play a key role in carbon sequestration by exporting organic matter to the deep ocean.
- Silicon (Si) Cycle and Climate Feedback
- dissolved silicate (Si(OH)₄) enters the ocean via weathering of silicate rocks.
- increased atmospheric CO₂ accelerates weathering, enhancing silicate input into oceans.
- diatoms remove dissolved Si from surface waters, influencing marine productivity and climate.
Describe some of the physical controls on phytoplankton productivity, and how they differ between high- and low-latitude ecosystems?
Bering and Chukchi Sea (High Latitude):
Strong seasonal variability
Diatoms thrive during ice melt, with nutrient upwelling fueling blooms.
Sargasso Sea (Subtropical,low latitude):
nutrient limitation = stable low productivity
Eddy-driven upwelling periodically enhances productivity.
Describe several methods used to make measurement of algal physiology?
1) stable isotope tracers
= (¹³C, ¹⁵N, ³²Si) track nutrient uptake
2) Mass Spectrometry and beta counters
= quantify Si and C utilization
3) field experiments
= assess environmental influences on diatom growth
Climate Change Impacts on Si Cycling and Diatoms
1) Ocean warming & stratification
= reduce nutrient mixing, limiting diatom growth.
2) Declining Arctic sea ice
= affects light availability and diatom community shifts.
3) Acidification impacts
= silica biomineralization, potentially affecting frustule formation.
Observations from Oceanographic Data (BATS & DBO Projects)
1) BATS (Bermuda Atlantic Time-series Study):
- PRODUCTIVITY SPIKES IN NOVEMBER due to nutrient upwelling.
2) DBO (Distributed Biological Observatory, Arctic):
- DECLINING TRENDS IN DIATOM BIOMASS AND SI UTILIZATION in warming Arctic waters.
Future Research Directions
o Investigate nutrient limitation in Arctic phytoplankton.
o Assess phytoplankton productivity under sea ice.
o Explore impacts of marine heatwaves on diatoms.
Other Stramenopiles
Describe the general structure of an Ochromonas cell.
Unicellular flagellate with two heterokont flagella,
golden-brown plastids,
a contractile vacuole.
What does the vegetative state of Dinobryon look like?
tree-like colonial arrangement of flagellated cells
each cell within a lorica
Chrysophytes produce a characteristic resting stage or cyst.
What is it called and what does it look like?
stomatocyst
- silica-walled
- single pore at apex
“A silica-walled resting stage with a single pore at the apex.”
What are the two genera of marine Raphidophyceans that are well-known for producing harmful algal blooms (HABs)?
Chattonella and Heterosigma.
What critical accessory pigment present in diatoms and other stramenopiles is absent in Xanthophyceans?
fucoxanthin
Some species of Xanthophyceans are found as siphonaceous coenocytes.
Describe this type of morphology.
large
multinucleate bodies with NO crosswalls
(ex// Vaucheria)
Brown Algae
do phaeophyceans have unicellular species ?
no
all brown algae are multicellular
what is the thallus of pseudoparenchymatous algae composed of ?
aggregations of branched filaments,
which RESEMBLE true tissues
Describe the 3 main components of the cell wall in brown algae and their functions
1) Alginic acid
- strength, flexibility, ion exchange, prevents desiccation
2) Cellulose
- structural support
3) Fucans
- possible role in attachment and protection
** sulfated polysaccharides
What compound is extracted from harvested phaeophyceans for industrial applications?
alginic acid
- used as a gelling/thickening agent
What pigment gives phaeophyceans their characteristic brown color?
What is their carbohydrate reserve material?
What is a physode?
fucoxanthin
laminarian
physode = a tannin containing cytoplasmic sphere that deters herbivory
What is phaeophyceans carbohydrate reserve material?
laminarian
What is a physode?
tannin-containing cytoplasmic spheres that deter herbivory
Describe the different modes of meristematic growth
Apical growth
- cell division at the tip
- (ex// fucus)
Intercalary growth
- growth between stipe and blade
- (ex// kelps)
where is the intercalary meristem located ?
between the stipe and the blade in kelps
Define ‘alternation of generations’.
a cycle alternating between haploid and diploid generations
Draw the 3 different types of life cycles in Phaeophyceans and indicate meiosis type.
**drawing on iPad
**drawing on iPad
1) Isomorphic
(Ectocarpus):
- sporic meiosis
2) Heteromorphic
(Laminaria- kelp):
- sporic meiosis with dominant sporophyte
3) Gametic meiosis
(fucus):
- no alternation of generations
What are plurilocs and unilocs?
Where are they found?
plurilocs (plurilocular sporangia/gametangia) =
mitotically produce spores/gametes
–> exist on both sporophyte and gametophyte
unilocs (unilocular sporangia) =
meiosis occurs, producing haploid spores
–> exist only on sporophyte
What is the primary world distribution of kelp with air bladders?
cold temperate coastal waters
especially pacific coasts of north and South America
describe tissue differentiation in kelp thalli
meristoderm = outermost
- for photosynthesis
- pigmented cells
cortex = between
- storage and transport
- colourless cells
medulla = center
- sieve elements for nutrient transport
- conduction of solutes
intercalary meristem
- stipe/blade junction
Red Algae
What is the role of encrusting coralline red algae in coral reef ecosystems?
stabilize reefs
- by cementing coral fragments and providing habitat for marine organisms
A crustlike coralline red algae has been found deeper than any other photosynthetic eukaryote (at 210 m deep in the Bahamas).
Explain how this alga can grow at depths where there is only ~0.0005% of surface light intensity.
contains phycoerythrin which absorbs blue and green light efficiently
commercial uses of red algae
pharmaceuticals
human food - nori in sushi
agar and carrageenan production
Describe thallus organization and growth modes in red algae.
1) early forms
2) more complex forms are still structurally simple
3) no intercellular cytoplasmatic connections
4) Bangiophyceans = no special meristematic region, cell division almost anywhere in the body = diffuse growth
5) Florideophyceans (filamentous)
- apical growth
– uniaxial body (delicate)
- single branched filament
– mulitaxial body (more robust/fleshy)
- multiple filamentous axes
**pictures
Describe the extracellular matrix (ECM) in red algae.
flexible and softer than other algal coverings bc of this gel-like component
cellulose microfibrils
(minor component)
amorphous gel-like mixture
(largest component)
Some may also deposit CaCO3
Do red algal cell have intercellular connections that allow exchange of solutes and gases between cells, such as plasmodesmata?
no intercellular connections, but have proteinaceous plugs in between cells instead
What are pit plugs?
How many kinds are there?
proteinaceous plugs between cells
provide structural link between cells
not for intercellular communication
primary pit plugs
- between sister cells
- structural link
secondary pit plugs
- between non-sister cells and red algal parasites and hosts
- exchange information and structural integrity
Describe 5 unique features of the cell biology of red algae
(excluding the triphasic life cycle).
lack centrioles
have pit plugs
cell elongation and repair
- ECM material
- If cell in middle of filament dies and remains of its ECM is intact, cells immediately above and below divide and fuse to repair the filament
Multinucleate - undergo mitosis without cytokinesis
Endoreduplication
- polyploid nuclei
phycoerythrin - for deep water activity where it can harvest blue and green light v efficiently
What is the most abundant pigment (in addition to chlorophyll a)
and the reserve material in red algae?
phycoerythrin
Floridian starch (in cytoplasm)
Using a labeled diagram, describe the biphasic life cycle of Bangiophyceans
**draw on iPad
Haploid gametophyte (n) → Diploid sporophyte (2n) → Carpospore production → New gametophyte formation.
Using a clearly labeled diagram, describe the triphasic life history of a Florideophycean red alga.
**draw on iPad
What is the evolutionary advantage of the triphasic life cycle?
allows for the amplification of a single fertilization event
Which one of the following multicellular stages are free-living: gametophyte, carposporophyte or tetrasporophyte?
gametophyte and tetrasporophyte are free living
the carposporophyte is not free living as it is on the female gametophyte
Green Algae
In what type of environments can you find Green Algae?
nearshore marine,
freshwater ponds,
rocky shorelines of eutrophic lakes and streams,
terrestrial surfaces,
in snow
= marine, freshwater, and terrestrial
also in symbiotic relationships
- fungi for lichens
- anemones
- sea slugs
Describe a Chlamydomonas cell.
unicellular
2 flagella
eyespot
storage inside chloroplast
stacked thylakoid membrane in plastid
pyrenoid
Name one unique characteristic of Green Algae.
storage INSIDE of the chloroplast
(in stroma)
What body types are found in this group?
Unicellular (e.g., Chlamydomonas).
Colonial (e.g., Volvox).
Filamentous (e.g., Cladophora).
Coenocytic (siphonous) (e.g., Codium).
Parenchymatous (e.g., Ulva).
What are the different kinds of cell coverings present in Green Algae?
Naked
Cellulose wall (Chlamydomonas has glycoprotein)
Scales
Some are calcified (Halimeda CaCO3)
Are there intercellular connections in some Green Algae?
What are they called?
yes, plasmodesmata
This intercellular pores that allow for cytoplasmic streaming
Using a labeled diagram, describe the zygotic life cyle of Chlamydomonas.
**drawing on iPad
Using a labeled diagram, describe the sporic life cycle of Ulva
drawing on iPad
Can Green Algae be found in symbiotic relationships?
Provide two examples.
yes
1) lichens (with fungi)
2) sea anemones
3) sea slugs (with vaucheria or codium)
What are the differences between Chlorophytes and Streptophytes?
chlorophytes =
- closed mitosis
- freshwater/marine and terrestrial
streptophytes =
- open mitosis
- freshwater and terrestrial
- closely related to land plants
Briefly provide characteristics of each one of the five major groups within Green Algae.
1) Prasinophytes
- earliest diverging modern green algae
- no unique characteristics
2) Trebouxiophyceae
- terrestrial and freshwater
- includes lichen symbionts and sloth hairs
3) Ulvophyceae
- includes largest and most conspicuous green algae
- can form blooms (green tides)
4) Chlorophyceae
- mostly freshwater
- diverse morphologies
5) Streptophyceae
- most closely related to land plants
