Protists: The Paramecium

by Matt Manchester                                                                                                                           

Reproduction

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.

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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.

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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.

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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 Fission


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