presentation on spirogyra

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3. (A) Scalariform conjugation
It is the most common type of
conjugation.
In this case, two parallel lying
filaments take part. Most of
the cells of the filaments
participate in conjugation at
the same time. Therefore, both
the filaments appear as adder-
like. Hence it is called
scalarifonn or ladder-like
conjugation
Sexual Reproduction
Sexual reproduction is isogamous. It takes
place by conjugation of non-flagellated
gametes.
Conjugations may be of two types:
(i) scalariform conjugation (ii) lateral
conjugation.
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4. The opposite cells develop lateral
outgrowths.
These outgrowths soon meet by
their tips. The end wall dissolves.
As a result, a
continuous conjugation tube is
formed between two cells of
different filaments.
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5. All cells of a filament can
produce gametangia.
A single gamete is formed from
each gametangium.
The protoplasmic contents of the cells
change into a single elliptical gamete.
The gamete producing cells are opposite
to each other in both filaments.
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6. Dioecious filaments: In this case, during
fusion, one gamete passes through the
conjugation tube. It reaches the apposite cell.
It fuses with the gametes of the other
filament. As a result, zygospore is formed in
one cell. The other stands remain empty. The
motile cell is called male gamete and other is
female gamete. Zygospore is formed in a cell of
the filament. Therefore, the two filaments are
dioecious.
Monoecious filaments: In this case, gametes
of both the
filaments move. The zygospore is formed in
the conjugation tube. Therefore, sex
distinction is not possible. Therefore, neither
one can be called male or female. Such
filaments are Monoecious.
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8. It occurs rarely. S. affinis.
In this case, a papilla like outgrowth is formed
in the transverse septum.
The outgrowth grows and breaks the septum.
A side passage is formed between the two
cells.
The upper cell acts male gametangium.
The lower cell acts as female gametangium.
The male gamete passes through this side
passage.
It fuses with female gamete and zygospore is
formed.
Also called chain conjugation.
Indirect lateral conjugation
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10. a. Direct lateral conjugation
It occurs between the two adjacent cells.
Upper cell functions as male gametangium.
Remains smaller.
The lower cell acts as female gametangium.
Increases in size.
The protoplast of male cell forms an
outgrowth.
This outgrowth elongates. Comes in contact
with transverse wall in between male and
female cells.
Later, it passes through it by forming an
opening in it. Thus conjugation tube is not
formed and the contents of male cell pass into
the female cell. As a result, zygospore is
formed.
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