[plants]: ALGAE Flashcards
General description of algae
chlorophyll-bearing simple thalloid autotrophic largely aquatic(both freshwater and marine) organisms
habitats
mainly aquatic
moist stones, soils, wood
in association with fungi(lichens) or animals(eg sloth bear)
example of colonial form
volvox
examples of filamentous forms
ulothrix, spirogyra
example of plant body-like formations
few marine forms like kelps
aspects of reproduction
vegetative, asexual,sexual
vegetative reproduction is by
fragmentation
each fragment develops a
thallus
thallus
a plant body that is not differentiated into stem and leaves and lacks true roots and a vascular system. Thalli are typical of algae, fungi, lichens, and some liverworts.
asexual reproduction is by
formation of different types of spores, the most common being the zoospores
their zoospores are
flagellated(motile) and on germination give rise to new plants
sexual reproduction takes place through
fusion of two gametes
example of same sized flagellated(motile) gametes
ulothrix
example of same sized non-flagellated(non-motile) gametes
spirogyra
isogamy
Isogamy is a form of sexual reproduction that involves gametes of similar morphology.
Because both gametes look alike, they generally cannot be classified as male or female.
anisogamy
Anisogamy is the form of sexual reproduction that involves the union or fusion of two gametes, which differ in size and/or form. The smaller gamete is male, a sperm cell), whereas the larger gamete is female, typically an egg cell. Anisogamy is common and widespread in multicellular organisms.
example of anisogamous species
eudorina
example of isogamous species
ulothrix, spirogyra
example of oogamous species
volvox, fucus
oogamy
It is a form of anisogamy (heterogamy) in which the female gamete (e.g. egg cell) is significantly larger than the male gamete and is non-motile.
uses of algae
- half of CO₂ fixation on earth by photosynthesis
- increase the level of dissolved oxygen in the atmosphere
- primary producers of energy-rich compounds for aquatic life forms
- 70 marine species are edible like laminaria, sargassum,porphyra
- certain marine red and brown algae produce hydrocolloids like algin(b.a) and carrageen(r.a)
- agar used in jellies and ice cream from Gelidium and Gracilaria
- chlorella, unicell alga, rich in proteins, used as a food supplement
hydrocolloids
water-holding substances
three main classes of algae
Chlorophyceae
Phaeophyceae
Rhodophyceae
the common name of Chlorophyceae
green algae
pigments of grp 1
chlorophyll a,b
stored food in grp 1
starch
cell wall composition of grp 1
cellulose(inner)
pectose(outer)
no. of flagella in grp 1
2-8
size and position of flagella in grp 1
equal and apical
habitat of grp 1
fresh, brackish, and saltwater
body forms of grp 1
unicellular, colonial, or filamentous
the shape of chloroplasts in grp 1
discoid plate-like reticulate spiral cup-shaped ribbon-shaped in diff species
most members of grp 1 have one or more storage bodies called
pyrenoids
pyrenoids
are located in the chloroplasts
proteinaceous centres surrounded by starch
some algae(grp 1) may store food in the form of
oil droplets
reproduction in grp 1
- fragmentation
- flagellated zoospores(from zoosporangia)
- isogamy, anisogamy, oogamy
examples of green algae
volvox spirogyra ulothrix chlamydomonas chara
the common name of Phaeophyceae
brown algae
major pigments in grp 2
chlorophyll a,c,
xanthophyll,
fucoxanthin
stored food in grp 2
mannitol
laminarin
cell wall composition in grp 2
cellulose(inner)
algin(gelatinous outer covering)
no. of flagella in grp 2
2
size and position of flagella in grp 2
unequal
lateral
habitats of grp 2
primarily marine
brackish, saltwater
freshwater(rare)
body forms of grp 2
simple branched filamentous forms(eg Ectocarpus)
to profuse branched forms(like kelps reaching even 100m)
colour variation of grp 2
olive green to different shades of brown
the protoplast of grp 2 contains
plastids
centrally located vacuole
nucleus
parts of grp 2
holdfast-attaches itself to the substratum
stipe-stalk like structure
frond-leaf-like photosynthetic organ
vegetative reproduction in grp 2
fragmentation
asexual reproduction in grp 2
pear-shaped biflagellate zoospores having two unequal laterally attached flagella
sexual reproduction in grp 2
isogamy
anisogamy
oogamy
union of gametes of grp 2 takes place in
water or oogonium in oogamous species
the shape of gametes in grp 2
pyriform(pear-shaped)
2 unequal lateral flagella
examples of brown algae
ectocarpus, dictyota laminaria sargassum fucus
the common name of Rhodophyceae
red algae
major pigments of grp 3
chlorophyll a,d
r-phycoerythrin
habitats of grp 3
mostly marine and conc in warmer areas
brackish water
freshwater(some)
both well-lighted regions and great depths
stored food in grp 3
floridean starch (similar to amylopectin and glycogen in structure)
cell wall composition of grp 3
cellulose
pectin
polysulphesters
the body form of grp 3
the red thalli of most red algae are multicellular and some have complex body organisation
vegetative reproduction in grp 3
fragmentation
asexual reproduction in red algae
non-motile spores
sexual reproduction in red algae
non-motile gametes(oogamy)
followed by complex post fertilisation developments
examples of red algae
gelidium
gracilaria
porphyra