Chlorophyta Flashcards
Habitat of Chlorophyta
Freshwater (90%)
Marine (10%)
Chlorophyta pigments
Similar to higher plants with chlorophyll a and b, as well as carotenoids (B-carotene, siphonoxanthin, astaxanthin
B-carotene and astaxanthin colour cells ___________.
_____% of cellular content in Dunaliella sp.
Orange-red
8-12
(ROSE LAKE)
If there is a flagellum, then it cannot be____
Cyanobacteria
What other colour can green algae appear as?
Red
Still green algae, but with lots of B-carotene
Animals don’t synthesize carotenoids, but instead _________
Acquire through food chain
________ are responsible for the colouring in fish, crustaceans and birds (flamingos)
Hematochromes
In human health, carotenoids are _______
Antioxidants
B-carotene has a pro-vitamin A function
Lutein/Zeaxanthin constitute macular pigment in the eye-> may reduce age-related eye disease and cataracts
Chloroplast structure in Chlorophyta (green algae)
Chloroplasts surrounded by double membrane chloroplast envelope
Starch is formed in the chloroplasts in association with a Pyrenoid-> storage product in the chloroplast instead of in the cytoplasm
Starch similar to higher plants: amylose and amylopectin
Contractile vacuoles
-usually in biflagellate genera there are two contractile vacuoles at the base of the flagella
-in fresh water (hypotonic) environment the inflow of water is compensated by the water that is pumped out by the contractile vacuoles
-contractile vacuoles may also function in removing waste form the cells
Eyespot or stigma
Most flagellated cells that show phototactic movement have this
-eye post consists of lipid droplets (globules)-> orange-red from carotenoids
Move cell in the direction of light
Phototaxy of Chlorophyta
-eyespot utilizes photoreceptor-> signalling
-light excitation causes isomerization of retinols protein -> triggers conformation change
-light initiates a signal that causes influx of Ca2+ into flagella
-two flagella respond differently to Ca2+ increase inside cytoplasm
-one flagellum beats faster, other slower
-difference in activity causes the cell to turn toward the light
Asexual reproduction happens when
Rapid and typical in good environmental constitutions when very rapid population growth is advantageous
Fragmentation
Asexual reproduction of colonies or filaments into two or more parts, each part becoming a new colony
Zoosporogenesis
Asexual reproduction of flagellated zoospores inside vegetative cells
Cell contents become densely coloured, then divide into several spherical zoospores which escape through a hole or tube in the cell wall
Zoospores may also form in ______ in younger parts or filaments
Sporangia
Aplanospores
Asexual reproduction
Develop from the division of parent cell into daughter cells with separate cell walls-> function like zoospores but not motile: germinate into new individuals
May remain together in a loosely-held mucilaginous colony
Autospores
Asexual reproduction
Develop within parent cell wall, same shape as the parent cell
Common in unicellular green algae
Chlamydomonas nivalis (snow algae) reproduce in which way
Aplanospores
Coenobia
Asexual reproduction
Colonies with a definite number of symmetric cells (volvox)
Individual cells enlarge, but no division of vegetative cells in colony
Individuals may grow as unicels in absence of predators-> chemicals from the digestive track of daphnia induce colony formation
What is the advantage of existing as a colony
More surface area to stay afloat
Variations of sexual reproduction in Chlorophyta
Isogamous-(+-, look the same)
Ansiogamous-distinguishable gametes (same size)
Oogamy-large egg, small sperm
Basic sexual reproduction life cycle of Chlorophyta is _______
Zygotic
Zygote is only diploid cell in cycle
Meiosis occurs in zygote
Contrast zoo spores and isogametes in the chlamydomonas sexual cycle
Zoospores- motile spore that continues the asexual cycle of haploid forms (+ or -) dividing mitotically into more haploid forms
Isogametes- motile spores that that take a + and - gamete, go through Plasmotomy and karyogamy to produce a zygospores which then divides meiotically and germinates
