Question

пресноводные и морские одноклеточные животные отличаются работой сократительных вакуолей.Сократительные вакуоли пресноводных одноклеточных животных при комнатной температуре проделывают весь цикл пульсации за 10-15 секунд.При этом они выводят из организма объём жидкости ,равный объёму их тела.У морских одноклеточных животных сократительная вакуоль пульсирует очень редко,а иногда отсутствует вовсе.ОБЪЯСНИТЕ ПРИЧИНЫ РАЗЛИЧИЙ В РАБОТЕ СОКРАТИТЕЛЬНЫХ ВАКУОЛЕЙ ПРЕСНОВОДНЫХ И МОРСКИХ

Answer 1

В пресноводных одноклеточных они есть, а в морских кажется нет. Клетка одноклеточного имеет определенный солевой состав (концентрацию соли). Но амеба живет в пресной воде, и вода за законами физики постоянно заходит в клетку, уменьшая в ней количество соли, нарушая солевой состав. Чтобы его регулировать, постоянно сокращается вакуоля и выталкивает лишнюю воду. А в соленой воде количество соли в воде и в одноклеточном практически одинаковое

Answer 2

Differences in the Functioning of Contractile Vacuoles in Freshwater and Marine Single-Celled Animals

Freshwater and marine single-celled animals differ in the functioning of their contractile vacuoles. Contractile vacuoles are specialized organelles responsible for regulating water balance in these organisms. They help maintain osmotic balance by expelling excess water from the cell.

Freshwater Single-Celled Animals: In freshwater single-celled animals, the contractile vacuole undergoes pulsations or contractions at a relatively high frequency. At room temperature, the entire pulsation cycle of the contractile vacuole is completed within 10-15 seconds. During each pulsation, the contractile vacuole expels a volume of fluid equal to the volume of the organism's body. This rapid and efficient expulsion of excess water helps prevent the cell from bursting due to osmotic pressure.

Marine Single-Celled Animals: In contrast, the functioning of the contractile vacuole in marine single-celled animals is different. The contractile vacuole in these organisms pulsates much less frequently and sometimes may even be absent. The reasons for these differences in the functioning of contractile vacuoles between freshwater and marine single-celled animals can be attributed to the following factors:

1. Osmotic Environment: Marine environments have a higher salt concentration compared to freshwater environments. As a result, marine single-celled animals are exposed to a more isotonic or hypertonic environment, where the concentration of solutes outside the cell is relatively higher than inside the cell. This osmotic environment reduces the need for excessive water expulsion by the contractile vacuole, as the cells are less likely to take in excess water.

2. Water Availability: Freshwater environments have a higher water availability compared to marine environments. Freshwater single-celled animals constantly face the challenge of osmotic gain of water due to the hypotonic nature of their environment. Therefore, they require more frequent and efficient water expulsion by the contractile vacuole to maintain osmotic balance.

3. Adaptation to Osmotic Stress: Freshwater single-celled animals have evolved to live in environments with fluctuating osmotic conditions. Their contractile vacuoles have adapted to rapidly respond to changes in water availability and efficiently regulate water balance. Marine single-celled animals, on the other hand, have adapted to the relatively stable osmotic conditions of the marine environment, which may explain the reduced frequency or absence of contractile vacuole pulsations.

In summary, the differences in the functioning of contractile vacuoles between freshwater and marine single-celled animals can be attributed to the osmotic environment, water availability, and adaptation to osmotic stress. Freshwater organisms require more frequent and efficient water expulsion to counteract osmotic gain, while marine organisms experience less osmotic stress and therefore have reduced or absent contractile vacuole pulsations.

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