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The chlorophyceae are one of the largest groups of the
green algae, containing over 2500 species. They come in all sizes and
shapes, ranging from single celled through round colonies and in filamentous
forms.
Technically they are recognized by these traits...
- Cell division is by a
phycoplast
of microtubules that form
parallel to the plane of division
- The spindle disintegrates after
anaphase separation or In some species the there is a
furrowing of the cytoplasm membrane oriented by the
phycoplast
while in still other species
vesicles coalesce to form a cell plate that divides the
cell.
- If motile cells exist, then the
flagella are inserted anteriorly and from the basal
bodies, 4 bundles of microtubules cross out in a
'cross-my-heart' or x configuration
- Life cylcle is zygotic
meiosis
The 3 major groups include:
Volvocales,
Chaetophorales, & Chlorococcales - they make up more than half of all
chlorophyceans and have an offset flagellar arrangement (1 o'clock-7 o'clock)
of flagella.
Chlorellales & Chlorococcales
- These algae have opposed flagellae (12 o'clock-6 o'clock), though
some have only vestigial flagellae and so have not been definitively associated
with this group.
Oedogoniales - Members
of this smallest group have a complex multiflagellate crown on their swimming
spores. All are filamentous, oogamous, and have net-like chloroplasts.
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