midterm 2 Flashcards
Describe the ecological importance of dinoflagellates.
Major contributors to marine primary production. Essential symbionts in coral reefs (Symbiodinium). Can form harmful algal blooms (HABs), including red tides. Some species bioluminesce, affecting predator-prey interactions.
What is the difference between a thecate (armoured) and athecate (unarmoured) dinoflagellate?
Thecate (armoured): Have cellulose thecal plates within alveoli. Athecate (unarmoured): Lacking cellulose plates, more flexible.
What are thecal plates made of?
Composed of cellulose and located within alveoli under the plasma membrane.
What are the morphological differences between a desmokont and a dinokont cell?
Desmokont: Two flagella emerge apically. Dinokont: Flagella emerge from separate grooves (cingulum and sulcus), common among dinoflagellates.
Describe the pusule and its function.
A membrane-bound organelle connected to the exterior, involved in excretion, osmoregulation, and fluid balance.
Describe motility in dinokont dinoflagellates.
Use two flagella: Transverse flagellum (in cingulum) generates forward motion and rotation. Longitudinal flagellum (in sulcus) aids in steering.
Define the term Trichocyst.
Ejectable rod-like structures used for defense.
Define the term Scintillon.
Organelles containing luciferase and luciferin for bioluminescence.
Define the term Peridinin.
A unique xanthophyll pigment aiding in photosynthesis.
Define the term Sulcus.
Longitudinal groove where one flagellum is located.
Define the term Cingulum.
Equatorial groove housing the transverse flagellum.
Define the term Alveoli.
Flattened vesicles beneath the plasma membrane, providing structure.
Define the term Amphiesmal.
The combination of alveolar vesicles and membranes.
Define the term Zooxanthellae.
Symbiotic dinoflagellates living in corals.
Define the term Planozygote.
Motile zygote formed after gamete fusion.
Define the term Hypnozygote.
Thick-walled, dormant cyst for survival.
How is bioluminescence produced in dinoflagellates?
Luciferase oxidizes luciferin, producing a flash of blue light.
Describe the life cycle of a typical dinoflagellate.
Include vegetative cells (haploid), gametes, planozygote, hypnozygote, and cyst formation.
What is 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?
Ability to store nutrients and regulate buoyancy. Efficient swimming to access light and nutrients. Mixotrophy allows utilization of organic carbon sources.
How do you define a photosynthetic stramenopile?
A heterokont alga with chlorophyll a & c, fucoxanthin, and a silica cell wall.
Why are diatoms important in the ecology and biogeochemistry of the oceans?
Contribute ~20% of global carbon fixation. Key players in the silica cycle and biogenic sedimentation.
In which environments do planktonic diatoms flourish?
Cold, nutrient-rich waters (upwelling zones, high-latitude seas).
Describe the two main diatom forms.
Centric diatoms: Radially symmetric, often planktonic. Pennate diatoms: Bilateral symmetry, often benthic.
Describe the different parts of the cell wall in diatoms.
Frustule: Two-part silica shell. Epitheca: Larger upper valve. Hypotheca: Smaller lower valve. Raphe: Slit for movement in some pennate diatoms.
What advantages does the cell wall confer to a diatom cell?
Protection from grazing. Structural integrity. Resistance to enzymatic attack.
What is the frustule made of?
Silicon dioxide (SiO₂).
Can diatoms produce toxic blooms?
Yes, some species (Pseudo-nitzschia) produce domoic acid, causing amnesic shellfish poisoning.
Describe asexual reproduction in diatoms.
Each daughter cell inherits one half of the parent frustule and synthesizes a new smaller half.
Explain the typical reduction in cell size that diatoms experience over generations.
Over successive divisions, diatom cells decrease in size until they undergo sexual reproduction.
Describe the life cycle of a centric diatom.
Oogamous sexual reproduction, gametic meiosis.
Describe the life cycle of a pennate diatom.
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.
Describe how planktonic diatoms can retard sinking.
Oil droplets for buoyancy. Chain formation increases drag. Spines and projections reduce sinking speed.
Can diatom spores develop under low Si availability?
No, silica is required for frustule development.
Describe the term Raphe.
Slit in pennate diatoms for movement.
Describe the term Areolae.
Pores in the frustule for nutrient exchange.
Describe the term Rimoportulae.
Tubular pores for polysaccharide excretion.
Describe the term Fultoportulae.
Involved in buoyancy control.
Describe the term Silica deposition vesicle.
Organelle for frustule synthesis.
Describe the term Resting cell.
Dormant stage for survival.
What is the distinctive accessory pigment and storage compound in diatoms?
Fucoxanthin and chrysolaminaran.
Under what environmental conditions do diatoms switch to heterotrophic nutrition?
Low light conditions (e.g., under ice, deep water, sediment layers).
Where are biogenic siliceous sediments most common in the oceans?
Upwelling zones, polar regions, and deep-sea basins.
What does the term ‘silicate ocean’ refer to?
Regions where diatoms dominate over carbonate-secreting phytoplankton.
What is the role of diatoms in biogeochemical cycles?
Diatoms dominate silicon (Si) cycling in marine ecosystems. Diatom photosynthesis contributes ~20% of global primary production, comparable to terrestrial rainforests. Diatoms play a key role in carbon sequestration by exporting organic matter to the deep ocean.
What is the silicon (Si) cycle and its 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.
What are the differences in phytoplankton productivity at high vs. low latitudes?
Bering and Chukchi Sea (High Latitude): Strong seasonal variability in phytoplankton productivity. Diatoms thrive during ice melt, with nutrient upwelling fueling blooms. Sargasso Sea (Subtropical, Low Latitude): Stable low productivity due to nutrient limitation. Eddy-driven upwelling periodically enhances productivity.
How is diatom physiology measured?
Stable isotope tracers (¹³C, ¹⁵N, ³²Si) track nutrient uptake. Mass spectrometry and beta counters quantify Si and C utilization. Field experiments assess environmental influences on diatom growth.
What are the impacts of climate change on Si cycling and diatoms?
Ocean warming & stratification reduce nutrient mixing, limiting diatom growth. Declining Arctic sea ice affects light availability and diatom community shifts. Acidification impacts silica biomineralization, potentially affecting frustule formation.
What observations have been made from oceanographic data regarding diatoms?
BATS (Bermuda Atlantic Time-series Study): Productivity spikes in November due to nutrient upwelling. DBO (Distributed Biological Observatory, Arctic): Declining trends in diatom biomass and Si utilization in warming Arctic waters.
What are future research directions for diatoms?
Investigate nutrient limitation in Arctic phytoplankton. Assess phytoplankton productivity under sea ice. Explore impacts of marine heatwaves on diatoms.
Describe the general structure of an Ochromonas cell.
Unicellular flagellate with two heterokont flagella, golden-brown plastids, and a contractile vacuole.
What does the vegetative state of Dinobryon look like?
Tree-like colonial arrangement of flagellated cells, each within a lorica.
What is the resting stage produced by chrysophytes called?
Stomatocyst: A silica-walled resting stage with a single pore at the apex.
What are the two genera of marine Raphidophyceans known for producing harmful algal blooms?
Chattonella and Heterosigma.
What critical accessory pigment is present in diatoms and other stramenopiles but absent in Xanthophyceans?
Fucoxanthin.
Describe the morphology of siphonaceous coenocytes in Xanthophyceans.
Large, multinucleate bodies without cross-walls (e.g., Vaucheria).
Do phaeophyceans have unicellular species?
No, all brown algae are multicellular.
What is the thallus of pseudoparenchymatous algae composed of?
Aggregations of branched filaments, resembling true tissues.
Describe the 3 main components of the cell wall in brown algae.
Alginic acid: Flexibility and ion exchange. Cellulose: Structural support. Fucans: Possible role in attachment and protection.
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?
Pigment: Fucoxanthin.
What is the carbohydrate reserve material in phaeophyceans?
Reserve material: Laminarin.
What is a physode?
Tannin-containing cytoplasmic spheres that deter herbivory.
Describe the different modes of meristematic growth in brown algae.
Apical growth: Cell division at the tip (e.g., Fucus). Intercalary growth: Growth between stipe and blade (e.g., kelps).
Where is the intercalary meristem located in kelps?
Between the stipe and blade in kelps.
Define ‘alternation of generations’ in brown algae.
A life cycle alternating between haploid gametophyte and diploid sporophyte stages.
Draw the 3 different types of life cycles in Phaeophyceans and indicate meiosis type.
Isomorphic (Ectocarpus): Sporic meiosis. Heteromorphic (Laminaria): Sporic meiosis with dominant sporophyte. Gametic (Fucus): No alternation of generations.
What are plurilocs and unilocs?
Plurilocular sporangia/gametangia: Mitotically produced spores/gametes. Unilocular sporangia: Meiosis occurs, producing haploid spores.
What is the primary world distribution of kelp with air bladders?
Cold-temperate coastal waters, especially the Pacific coasts of North/South America.
Describe tissue differentiation in kelp thalli.
Meristoderm: Outer layer, photosynthetic. Cortex: Middle layer, storage and transport. Medulla: Inner layer, contains sieve elements for nutrient transport.
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.
How can a crustose coralline red alga grow at 210 m depth?
Contains phycoerythrin, which absorbs blue and green light efficiently.
Indicate two main commercial uses of red algae.
Food (e.g., Nori, sushi). Agar and carrageenan production.
Describe the extracellular matrix (ECM) in red algae.
Composed of cellulose, agar, and carrageenan.
Describe the biphasic life cycle of Bangiophyceans.
Haploid gametophyte (n) → Diploid sporophyte (2n) → Carpospore production → New gametophyte formation.
In what type of environments can you find Green Algae?
Found in marine, freshwater, and terrestrial habitats. Present in symbiotic relationships (e.g., lichens, sea slugs).
Describe a Chlamydomonas cell.
Unicellular, biflagellated freshwater alga. Cup-shaped chloroplast with a pyrenoid. Stigma (eyespot) for phototaxis.
Name one unique characteristic of Green Algae.
Storage of starch inside the chloroplast, unlike other algal groups.
What body types are found in Green Algae?
Unicellular, multicellular, and colonial forms.
What habitats are Green Algae found in?
Green Algae are found in aquatic and terrestrial habitats.
Describe a Chlamydomonas cell.
It is a unicellular, biflagellated freshwater alga with a cup-shaped chloroplast containing a pyrenoid and a stigma (eyespot) for phototaxis.
Name one unique characteristic of Green Algae.
They store starch inside the chloroplast, unlike other algal groups.
What body types are found in Green Algae?
Unicellular (e.g., Chlamydomonas), Colonial (e.g., Volvox), Filamentous (e.g., Cladophora), Coenocytic (e.g., Codium), Parenchymatous (e.g., Ulva).
What are the different kinds of cell coverings present in Green Algae?
Naked cells (no wall), Cellulose walls, Scales, Calcified exteriors (e.g., Halimeda).
Are there intercellular connections in some Green Algae? What are they called?
Yes, plasmodesmata occur in some streptophytes.
Describe the zygotic life cycle of Chlamydomonas.
Haploid vegetative cells → Isogametes fuse → Diploid zygote → Meiosis restores haploid phase.
Describe the sporic life cycle of Ulva.
Isomorphic alternation of generations: Diploid sporophyte (2n) produces haploid spores; Haploid gametophyte (n) produces gametes.
Can Green Algae be found in symbiotic relationships? Provide two examples.
Yes, examples include lichens (with fungi) and sea slugs (with Vaucheria or Codium).
What are the differences between Chlorophytes and Streptophytes?
Chlorophytes have closed mitosis, radial symmetry, and are mostly marine; Streptophytes have open mitosis, plasmodesmata, and are closest to land plants.
Briefly provide characteristics of each one of the five major groups within Green Algae.
Prasinophytes: Early-diverging flagellates; Chlorophyceae: Mostly freshwater, diverse morphologies; Trebouxiophyceae: Terrestrial and freshwater, includes lichen symbionts; Ulvophyceae: Large macroscopic marine algae (e.g., Ulva); Streptophytes: Evolutionary link to land plants.
