Q.3. Give a short account of respiration, excretion and osmoregulation in Paramecium.
Ans.3. 1. Respiration
The oxygen dissolved in surrounding water diffuses in through the general body surface and CO2 is liberated in a similar manner.
2. Excretion
The waste products such as urea, uric acid and other nitrogenous compounds, produced as a result of catabolic activities of the body, also diffuse out through the general body surface.
3. Osmoregulation
The amount of water in the body is controlled by the two contractile vacuoles present one on either end of the body. Excess of water from cytoplasm is collected in the microtubules of endoplasmic reticulum. From here water is passed on to the nephridial tubules and to feeder canals. In feeder canals it accumulates in the ampullae. On getting filled the ampullae discharge it in the contractile vacuole. The vacuole enlarges gradually by receiving Water.
When grown to its maximum size, vacuole contracts (systole) and empties its water to the exterior through the canal that connects it with a pore in the pellicle. When the vacuole is in a state of diastole i.e. fully distended, the feeding canals disappear as small streaks soon after the systole. The contractile vacuoles expand and contract at regular intervals assisted by the myofibrils. The posterior contractile vacuole pulsates much faster than the anterior contractile vacuole, probaby because of large amount of water reaching the posterior region of the cytopharynx.
4. Irritability or Sensitivity
Paramecium exhibits great sensitivity to the various stimuli and its movements are more definite. The response is either negative if the stimulus is harmful or positive if the stimulus is useful. If the anterior end of Paramecium is touched with a pointed needle or some strong chemical is added it moves away trying to avoid the stimulus. Similarly, negative response is shown towards strong light, ultraviolet rays and towards increased and decreased temperature. A positive response is shown towards weak electric currents and water currents.
BSc 1st Year Lower Non-chordates Paramecium Sample Model Practice Question Answer Papers