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

Explain the failure of endodontic Treatment, Explain the Failure of Endodon...

Explain the Failure of Endodontic Treatment 1. Microorganisms are left inside the canal - Improper/inability of cleaning and shaping, - Source of infection could be: peri

Depleted (vulnerable) species, Depleted (Vulnerable) Species These are...

Depleted (Vulnerable) Species These are the species whose numbers are greatly reduced from those of the recent past, and they are continuing to decrease. It is the continued d

Explain three main steps for a good study of genetic tree, What are the thr...

What are the three main steps for a good study of a genetic family tree? Step 1: to determine whether the studied phenotypical form has a dominant or recessive pattern. Step

Major cell types that form the osseous tissue, Q. What are the three major ...

Q. What are the three major cell types that form the osseous tissue? What are their functions? The three major cell types of the osseous tissue are the osteocytes, the osteobla

Explain type 2 diabetes mellitus, Q. Explain Type 2 Diabetes Mellitus? ...

Q. Explain Type 2 Diabetes Mellitus? It is the most common form of diabetes accounting for 90-95% of patients with diabetes. Type 2 Diabetes Mellitus was previously called as N

Type of bacterial food poisoning, Type of bacterial food poisoning In...

Type of bacterial food poisoning Infection type: The infection type results from the release of toxin in the bowel by microorganisms taken in foods, e.g., Salmonella or Vibr

What is single s2, What is Single S 2 In cyanotic TOF, S, consists enti...

What is Single S 2 In cyanotic TOF, S, consists entirely of A, as P, is attenuated by a deformed pulmonary valve when there is valvar steuosis and aorta is placed anteriorly re

Gorgonids, Gorgonids yield chemicals like prostaglandins, medically useful ...

Gorgonids yield chemicals like prostaglandins, medically useful for birth control, prevention of peptic ulcers, treatment of asthma, regulation of blood pressure, etc. Sponges are

Elaborate the internal vascular circulation of an eye, Elaborate the intern...

Elaborate the internal vascular circulation of an eye. Retinal vessels are derived from central retinal artery and are distributed within the inner two-third of retina. Outer o

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