Contractile vacuoles - excretion, Biology

Assignment Help:

Contractile Vacuoles - Excretion

Contractile vacuoles are always found in freshwater protozoans and sponges, but are frequently absent in their marine counterparts. Since a freshwater animal is hyperosmotic to the medium (freshwater) and its surface is permeable to water, it should continually endeavour to pump out the excess water that enters osmotically. When a freshwater protozoan is transferred to dilute sea water, the vacuolar activity decreases. In those marine species that have a contractile vacuole (e.g., some ciliates), vacuolar output increases with dilution of the sea water.

The fluid present in the contractile vacuole of freshwater protozoans is hypoosomotic to the surrounding cytoplasm, though still hyperosmotic to freshwater. These observations are consistent with the hypothesis that contractile vacuoles are primarily organs of water balance and function as pumps to remove excess osmotic water. Any role they might play h the excretion of nitrogenous wastes, which is mainly ammonia-in protozoans and sponges, is considered to be secondary.


Related Discussions:- Contractile vacuoles - excretion

Segments of environment:, Segments of Environment: The environment ...

Segments of Environment: The environment is not a simple distribution of gases but is highly complex and structured. It comprises of four segments:   Lithosphere

Illustrate thallium scintigraphy, Q. Illustrate Thallium Scintigraphy? ...

Q. Illustrate Thallium Scintigraphy? It is often done with SPECT (single photon emission computed tomography) which further increases the sensitivity. However, a stress test w

How the visual images are projected, Since the visual images are projected ...

Since the visual images are projected in an inverted manner on the retina why don't we see things upside down? As the crystalline lens is a convex spherical lens it forms inver

Post-operative care of teeth, Post-operative care of teeth After implan...

Post-operative care of teeth After implant surgery, patients should be warned to expect:  Some swelling and possibly bruising.  Some discomfort which can usually be contr

Determine the width of attached gingiva at implant site, Width of Attached ...

Width of Attached Gingiva at Implant Site The zone of attached gingiva needs to be intact and of adequate width to protect (by separating) the tissue around the implant. If it

Explain prostaglandins, Prostaglandins Prostaglandins belong  to a sub...

Prostaglandins Prostaglandins belong  to a subclass of  lipids known  as the eicosanoids because of their structural similarities to  the C-20  polyunsaturated  fatty acids, t

Explain the features of alternaria, Explain the Features of Alternaria? ...

Explain the Features of Alternaria? 1. Alternaria colony is wooly and compact. Underside is very dark coloured. Colony colour is grayish green or black with gray edges rapidly

What are some common laboratory techniques, What are some common laboratory...

What are some common laboratory techniques? During the course of these laboratory sessions, you will be usual to become proficient in the performance of the following laborator

Dissimmilarity between an ecosystem and a biome, What is the difference bet...

What is the difference between an ecosystem and a biome?

Deficiency diseases-pregnancy toxaemia in sheep , Pregnancy toxaemia in she...

Pregnancy toxaemia in sheep (twin lamb disease, sleeping ewes disease, pregnancy ketosis). Pregnancy toxaemia is a multifactor disorder of energy metabolism affecting sheep du

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd