lecture 11 (phaeophyceans)

Question 1

do phaeophyceans have unicellular species?

Answer 1

no

Question 2

describe the thallus of pseudoparenchymatous algae

Answer 2

groups of filaments attached together to look like 3d growth, but isn’t really (eg. Desmerestia)

Question 3

what are the important ecological impacts of phaeophyceans?

Answer 3

they create underwater forests, with productivity rates of as much as 1kg C/m2/yr in macrocystis pyrifera

Question 4

what makes up the cell wall of phaeophyceans, and what are their functions?

Answer 4

alginic acid: strength, flexibility/toughness, prevents dessication, ion exchange
cellulose: structural support
fucans: anchoring zygotes and germlings to intertidal substrates

Question 5

what compound is extracted from harvested phaeophyceans for industrial applications, and what does it do? give examples

Answer 5

alginic acid -> as a gelling/thickening agent
eg. paint, show polish, food etc.

Question 6

what pigment gives the characteristic dark green/olive brown colour of phaeophyceans?

Answer 6

fucoxanthin

Question 7

describe the three different modes of meristematic growth:

Answer 7

single apical cell: one cell wide filament (ectocarpus)
apical meristem: more than one cell can grow in additional directions (e.g. fucus)
intercalary meristem: between stipe and blade(s), tissue grows in two directions (length and width)

Question 8

where is intercalary meristem located on the thallus?

Answer 8

between the stipe and the blade

Question 9

describe the life cycle of ectocarpus (and list the name on basis of meiosis and generation)

Answer 9

sporic meiosis, isomorphic alternation of generations
female and male (N) gametophytes have pleurilocular gametangium which release gametes (N). these fertilize, and become a 2N zygote. this becomes the sporophyte which can have pleurilocs or unilocs. pleurilocs release 2N zoospores that become more 2N sporophytes. Unilocs undergo meiosis and release N zoospores that become N gametophytes.

Question 10

describe the life cycle of fucus (and list the name on basis of meiosis and generation)

Answer 10

gametic meiosis
2N sporophyte has inside conceptacles antheridium and oogonium which both undergo meiosis to release egg (N) and sperm (N) which fertilize and become a 2N zygote that grows into a 2N sporophyte

Question 11

describe the life cycle of laminaria (and list the name on basis of meiosis and generation)

Answer 11

sporic meiosis, heteromorphic AOG.
microscopic (N) gametophytes release egg and sperm which fertilize, into a 2N zygote, this becomes a sporophyte which has unilocular sporangium, where meiosis occurs and releases N zoospores that become microscopic gametophytes

Question 12

define “alternation of generations”

Answer 12

the alternation between a sporophyte and a gametophyte (between gamete producing phase and not)

Question 13

what are pleurilocs and unilocs and where are they found?

Answer 13

pleurilocs are either pleurilocular gametangia (which produce gametes) found on the gametophyte or pleurilocular sporangia (which produce asexual zoospores) on the sporophyte
unilocs are unilocular sporangia (which produce zoospores or meiospores by meiosis) on the sporophyte

Question 14

draw and label a mature sporophyte in kelp (name all the parts)

Answer 14

holdfast, stipe, blade, pneumatocysts

Question 15

what is the primary world distribution of kelp with air bladders?

Answer 15

temperate coastal waters

Question 16

describe the three types of tissue differentiation in kelp thalli

Answer 16

meristoderm (outer pigmented layer)
cortex (colorless cells)
medulla (inner layer with sieve elements, translocates solutes/ions)