Protists: The Paramecium
by Matt Manchester
The Paramecium is capable of both sexual
and asexual reproduction as well as a rare method of nuclear reorganization called
Endomixis. The first method, sexual reproduction, is a two step process. The paramecium
first aligns itself with another paramecium, the outer cell walls and cilia over lap in a
side by side docking position.
Under control of the Micronucleus the
Macronucleus begins to degenerate in each of the two cells and the micronucleus forms a
new replicate of the individual DNA strings. The cells swap the new DNA duplicates and
thus share each others DNA. This process then terminates and each cell re-creates a
Macronucleus based on a combination of both the old and new DNA. At this point no new baby
Paramecium have been created but the identities of the paramecium have changed based on
the new DNA code. At this point the process could stop or move onto the Fission process
which is step two. This is a unique ability and if stopped at this point results in a
sharing of information that could increase the chances of survival.
The Paramecium now begins to stretch and
duplicate internal parts. This is what it looks like on the outside. This is known as
binary fission since it has two parts.
This is what it looks like on the inside,
the cell has produced a duplicate of everything and put a copy of each into both ends of
the Paramecium. The new Macronucleus then stretches into both ends having duplicated the
internal DNA material in mirror images. When this is complete the Micronucleus causes the
outer cell wall to start to pinch closed much the way the food vacuole pinches closed
around the food and detaches from the gullet. When the pinching is complete the two
paramecium can drift away from each other with only the development of cilia in the area
that was joined yet to be completed.
It must be noted that Conjugation creates
new cell personalities, Fission creates new cells.
Sexual Reproduction involves: 1 -
Conjugation, 2 - binary Fission
Asexual Reproduction involves: Binary
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