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

What is the advantage of that innovation, What is the main evolutionary inn...

What is the main evolutionary innovation presented by nematodes? What is the advantage of that innovation? The short evolutionary innovation of nematodes is the complete digest

Define the role of fluorine in human body, Define the role of Fluorine in H...

Define the role of Fluorine in Human Body? Fluorine is potentially a toxic element. Its essentiality for humans is not established although the role of fluoride in providing pr

Explain about the zygomycota - fungi, Explain about the Zygomycota - Fungi?...

Explain about the Zygomycota - Fungi? Fungi belonging to zygomycota are called zygomycetes. Hyphae in this sub-class are coenocytic. Asexual spores develop in sporangia at the

Zoology, find the habits and habitats of scyphas?

find the habits and habitats of scyphas?

What is linkage, What is linkage? Two genes are said to be under linkag...

What is linkage? Two genes are said to be under linkage, or linked, when they reside in the same chromosome. For instance, the research of the human genome discovered that t

Explain the differance between savanna and desert, Explain the differance b...

Explain the differance between savanna and desert? Savanna : Savanna is characterized by relatively low rainfall and pronounced dry seasons. This type of climate produces a b

Excreation, what is the role of liver for the metabolism of carbohydrates

what is the role of liver for the metabolism of carbohydrates

Autotomy and regeneration, Autotomy and Regeneration Shedding of body...

Autotomy and Regeneration Shedding of body parts in self-defense to avert the attention of the predator-enemy or in any other emergency is a type of autotomy (auto: self, tom

Define about calcium and osteoporosis, Define about Calcium and Osteoporosi...

Define about Calcium and Osteoporosis? Gain in bone mass occurs throughout childhood; however, during adolescent growth spurt, the gain in bone mass, as well as, calcium retent

Hmp shunt in erythrocytes, HMP shunt in erythrocytes HMP shunt in eryth...

HMP shunt in erythrocytes HMP shunt in erythrocytes is of importance due to the generation of NADPH, which maintains the glutathione (G-SH)  in  the reduced  state by  glutathi

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