Modes of respiration, Biology

Assignment Help:

Modes of Respiration

Many small organisms obtain oxygen by diffusion through their body surfaces. They do not have any specialised respiratory organs nor do they have blood circulation. Larger and more complex organisms, however, need specialised surfaces for gas exchange and a circulatory system that transports oxygen more readily than that possible by simple diffusion. Calculations based on metabolic demands and rate of diffusion in protoplasm show that simple diffusion is sufficient only to meet the demands of organisms not larger than 1 mm in diameter. These calculations appear reasonable when we see that animals like protozoans and flatworms that meet their respiratory requirements through diffusion are either quite small or have very low metabolic rates.

Giant land planarians may be 50 cm long but they are flat with very large surfaces in relation to mass, therefore, diffusion is sufficient to meet their oxygen demand. Coelentrates, corals and sponges often reach very large sizes but have very modest metabolic demands. Sponges and corals maintain a circulation of water by cilia over the surfaces of cells which line their canal systems. Thus sufficient gas exchange takes place without the aid of a circulatory system or respiratory pigments.


Related Discussions:- Modes of respiration

Buffalo-pox, Buffalo-pox The disease is caused by an orthopox virus, c...

Buffalo-pox The disease is caused by an orthopox virus, closely related to the vaccinia virus. It is not clear whether it should be considered a separate virus or not. By RE m

Explain the food security, Explain the Food Security? You were introduc...

Explain the Food Security? You were introduced to the concept of food security in Unit 2. Food security, we learnt, is access by all people at all times to enough food for an a

Define the htst pasteurization method, Define the HTST Pasteurization Metho...

Define the HTST Pasteurization Method? Rapid, high pasteurization is characterized by a pasteurization time in the order of seconds and temperatures of about 85° to 90°C or mor

Pox diseases, P o x diseases Small-pox in human beings and pox in a f...

P o x diseases Small-pox in human beings and pox in a few animal species are closely related to each other. It is shown by the fact that the vaccine for the prevention of sma

Phyletic lineage, Ask questiona brief assignment on it #Minimum 100 words a...

Ask questiona brief assignment on it #Minimum 100 words accepted#

Define hormonal imbalance as a factor for obesity, Define Hormonal imbalanc...

Define Hormonal imbalance as a factor for obesity? Certain diseases associated with secretion of hormones, e.g., hypothyroidism, hypogonadism and Cushing's syndrome exhibit obe

Describe the advantages of sulphur, Describe the advantages of sulphur ...

Describe the advantages of sulphur Sulphur also increases the oil content of crops such as flax and soyabeans. Disulphide linkages ( -S-S-) have recently been associated with

Zoology, Wheel organ of amphioxus.

Wheel organ of amphioxus.

Excretory system, what is the excretory organ in protozoa?

what is the excretory organ in protozoa?

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