Think and discuss: Paramecia that live in freshwater have contractile vacuoles, while those that live in salt water do not. Why do you think this is the case

See the answer below

Explanation:

The contractile vacuole primarily functions for the excretion of excess water in organisms that possess the organelle. Paramecia that lives in freshwater would need to constantly get rid of excess water that is likely to be entering the cell due to the fact that the ambient water is hypotonic to their cells. The cytosols of paramecia that live in freshwater have a higher solute concentration and hence, lower water potential than the surrounding freshwater.

The paramecia that live in salt water do not have a need for the contractile vacuole because the problem of excess water entering their cells may not arise. The salt water may not be hypotonic to the cytosol of the paramecia.

hey bro i looked it up on google the structure of the eye-spot in euglena viridie, e. ehrenbergii, and phacus pyriyorme is not as franzé haa described it. the so-called “crystal body” and “lens bodies” were not found in any of the individuals of the species examined by me. as earlier observers have stated, the eye-spot consists simply of a mass of pigment granules arranged in a single layer, and probably embedded in a protoplasmic framework, but the latter could not be seen, and its presence was only inferred from the fact that the pigment granules must be held together in some way, thd the eye-spot as a whole is capable of expansion, and that the pigment granules can be separated from each other.

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