eukaryotic algae, phytoplankton

Question 1

eukaryotic algae

Answer 1

• algae is a descriptive term not true taxa
• basal photosynthetic aquatic organisms
• holophytic (photosynthetic, chlorophyll a)
• fail to reach level of differentiation as plants
• unicellular, colonial or multicellular
• fastest growth rates (macrocystys, highest levels of C fixation)
• bicarbonate fixation
• base of most aquatic food chains

Question 2

evolution of photosynthesis

Answer 2

• evolved first as anoxygenic photosynthesis in bacteria
• evolution of ancestral cyanobacteria (chloroxybacteria) about 2.5bya, event brought reaction centre I and II together (historically one or the other in spp) allowing the evolution of oxygenic photosynthesis (water as electron donor)

Question 3

primary endosymbiotic event

Answer 3

• all modern day photosynthetic eukaryotes evolved from one endosymbiotic event of protist and ancestral cyanobacterium
• produced three lineages
• red alga, glaucophytes, green alga
• plastid has two membranes around it, derived from cyanobacterium cell membrane and outer membrane

Question 4

secondary endosymbiosis

Answer 4

• green and red alga ingested by secondary host
• secondary plastid has three or more membranes, outer membrane is chloroplastic ER
• nucleus and mitochondria usually degenerate, nucleus sometimes retained in reduced form, nucleomorph

Question 5

secondary endosymbiosis of green algae gave rise to

Answer 5

• euglenids, most contain green plastids, plastids have 3 membranes
• chlorarachinophytes, rare marine amoeboflagellates and flagellates, nucleomorph, plastid has 4 membranes

Question 6

secondary endosymbiosis of red algae gave rise to

Answer 6

• haptophytes (CaCO3 coating makes chalk), marine flagellates, plastids have 4 membranes
• cryptomonads, plastids have 4 membranes, nucleomorph
• stramenopiles, diatoms and macroalgae, plastid has 4 membranes
• apicomplexa, obligate intracellular parasite, apicoplast thought to be relic plastid
• dinoflagellate, plastid has 3 membranes

Question 7

subsequent endosymbiotic events, dinoflagellates

Answer 7

• dinoflagellate (derived from secondary endosymbiosis) lost ability to photosynthesis
• subsequent serial secondary endosymbiosis, dinoflagellate engulfed individual that derived from primary endosymbiosis
• subsequent tertiary endosymbiosis, dinoflagellate engulfed individual that derived from secondary endosymbiosis

Question 8

serial secondary endosymbiosis gave rise to

Answer 8

• Lepidopdinium chlorophorium, L. viride
• dinoflagellate lost ability to photosynthesise and engulfed green alga

Question 9

tertiary endosymbiosis gave rise to

Answer 9

• Durinskia agilis, D. baltica, dinoflagellate lost ability to photosynthesise and engulfed diatom
• Karlodinium (13spp.), dinoflagellate engulfed haptophyte
• Dinophysis (265 spp.), dinoflagellate engulfed cryptomonad

Question 10

organisms with 2 membranes around plastid

Answer 10

• green alga, red alga, glaucophytes (primary endosymbiosis)
• cyanobacterial cell membrane and cyanobacterial outer membrane
• phagosomal membrane lost
• peptidoglycan layer in between lost in all groups but glaucophytes

Question 11

organisms with 3 membranes around plastid

Answer 11

• euglenids and dinoflagellates (secondary endosymbiosis)
• cyanobacterial cell membrane, cyanobacterial outer membrane, phagosomal membrane (chloroplastid ER)

Question 12

organisms with 4 membranes around plastid

Answer 12

• cryptophytes, heterokontophyta etc
• cyanobacterial cell membrane, cyanobacterial outer membrane, red algal cell membrane (chloroplastid ER), nuclear membrane (chloroplastid ER, continuation from around nucelus, contains ribosomes)

Question 13

photosynthetic pigments

Answer 13

Chlorophyll a always present, accessory pigments:
- chlorophyll b, c (c1 + c2), d
- phycobiliproteins: phycocyanin and phycoerythrin (Cu or Fe subgroup)
- caotenoids: caroteins and xanthophylls

Question 14

evolution of possession of accessory pigments

Answer 14

• ancestral cyanobacteria had chlorophyll b and phycobiliproteins
• eukaryotic ancestor also had both
• subsequently one or the other was lost
• glaucophytes and red alga have phycobiliproteins
• green alga have chlorophyll b
• evolution of other pigments later on
• chlorophyll d found in some cyanobacteria, possibly evolved late

Question 15

thylakoid arrangement of red alga (and cyanobacteria)

Answer 15

• single, thylakoids not stacked
• girdling, one thylakoid wrapped around periphery
• phycobiloproteins large and project from surface

Question 16

thylakoid arrangement in cryptophytes

Answer 16

• paired
• no girdling

Question 17

thylakoid arrangement in dinoflagellates and diatoms

Answer 17

• 3-ply
• no girdling

Question 18

thylakoid arrangement in green algae and terrestrial plants

Answer 18

• over 4-ply, arranged into granal stacks
• rare in unicellular organisms

Question 19

glaucophytes

Answer 19

• thought to have evolved before red and green algal lineages
• retained peptidoglycan layer
• chlorophyll a, phycobilins, phycobilisomes
• chloroplasts called cyanelles, debate whether they are true organelles or symbionts (cyanelles = halfway, not as incorporated into host)
• 13 spp., 5 genera
• rare, freshwater

Question 20

chlorophytes (green algae)

Answer 20

• marine and freshwater
• multicellular and unicellular
• chlorophyll a and b
• cellulose cell wall
• flagella
• thylakoids 3-5 banded
• 4 classes
• class Charophycaea thought to have given rise to land plants

Question 21

rodophyta (red alga)

Answer 21

• oldest group of eukaryotic alga
• chlorophyll a, phycobiliproteins
• lack flagella and centrioles (evolved later)
• produces mucoid instead of flagella to help with spore/gamete dispersal
• mostly mutlicellular (red seaweeds important in tropics)
• single thylakoids
• gave rise to many other lineages, dinoflagellates, haptophytes, cryptomonads, diatoms etc

Question 22

dinophyta, dinoflagellates

Answer 22

• very important phytoplankton in temperate climates
• chlorophyll a and c2
• peridinin and neoperidin (carotenoids)
• autotrophic, heterotrophic or mixotrophic (both)
• biflagellate, cellulose plates under plasma membrane
• harmful algal bloom forming species
• form symbiotic relationships, zooxanthellae in corals
• chromosomes permanently condensed in nucleus, nuclear envelope persists in mitosis, dinomitosis (unique)
• bioluminescence
• special organelles, pusule (osmoregulation), ocellus (eyes, one species has a lens), nematocyst (stinging cells, cnidarians acquired it), trichocysts, muciferous bodies

Question 23

dinoflagellates, harmful algal blooms

Answer 23

• toxins from bloom can kill if ingested, colourless and odourless
• diarrhetic shellfish poisoning
• paralytic shellfish poisoning
• ciguatera fish poisoning
• sea water and shellfish monitored in shellfish fisheries

Question 24

spring algal blooms in UK

Answer 24

• succession
• first diatoms, grow very quickly then become nutrient limited (SiO2)
• dinoflagellatespredate on dead/ damaged diatoms
• zooplankton follow

Question 25

Euglenids

Answer 25

• primarily freshwater
• chlorophyll a and b
• heterotrophic or mixotrophic (only half acquired chloroplasts)
• mesokaryotic nucleus, no sexual reproduction
• pellicle, proteinaceous strips beneath plasmalemma
• moves through metaboly (twisting and stretching of the pellicle)

Question 26

Bacillariophycaea, diatoms

Answer 26

• very important temperate CO2 fixers, unicellular
• silica cell wall (SiO2), 2 frustules/valves (epitheca = upper, hypotheca = lower)
• cell wall resistant to enzymes, inedible when alive/undamaged
• majority autotrophic (freshwater heterotrophs feed on decaying marine vegetation)
• large cells often visible to naked eye
• can produce resting spores/cells when conditions are unfavourable
• chlorophyll a, c1 and c2, fucoxanthin
• release unsaturated fatty acids when about to die, changes into short chain fatty aldehydes, toxic to larval invertebrate predators
• one group produces harmful algal blooms, amnesic shellfish poisoning

Question 27

Prymnesiophycea, haptophytes

Answer 27

• very small
• important algal blooms in tropics, turns water milky white
• covered in CaCO3 scales/coccoliths, fixing CO2 into chalk deposits
• haptonema, similar to flagella but 6+1 microtubule arrangement
• chlorophyll a, c1/c2, beta-carotene, diatoxanthin, diadinoxanthin
• also called coccolithophorids
• produce toxins, phaeocystis, beach foam (anti-predatory from cell death)

Question 28

cryptophyceae

Answer 28

• marine and freshwater flagellates
• like low light levels, important primary producers in poles, under ice, in freshwater lakes in Antarctica (polar specialists)
• important in polar blooms
• chlorophyll a, c2, phycobiliproteins (unusual)
• contains nucleomorph, remnant red alga nucleus between chloroplastid ER
• asymmetrical cells, ‘swaying’ swimming motion
• ejectosomes
• mixotrophic