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

Predict the outcome of future testing, A hypothesis can be used to predict ...

A hypothesis can be used to predict the outcome of future testing. Which type of hypothesis is easier to test? A. It is easier to specify and test for a difference between two outc

Cell with a euploid number of chromosomes, A cell with a euploid number of ...

A cell with a euploid number of chromosomes contains: A.one half of a complete set of chromosomes B.several complete sets of chromosomes C.the correct number of chromosomes D.two c

Centrosome, structure of centrosome and work

structure of centrosome and work

Explain an adaptation to terrestrial life, Why can the allantois be conside...

Why can the allantois be considered an adaptation to terrestrial life? The allantois is an adaptation to dry land because in embryos of oviparous terrestrial beings, like repti

Carbon filtration or activated carbon process, Activated carbon has a much ...

Activated carbon has a much higher adsorption capacity than other materials. Carbon adsorbs objectionable odours, flavours, organic compounds and many hazardous chemicals. There

Parthenocarpy, Parthenocarpy It is generally observed that the fruit d...

Parthenocarpy It is generally observed that the fruit develops after fertilization and it has fertile seeds inside it. However, this is not always so. Fruits of certain variet

Oceanic islands, Oceanic islands are interesting and somewhat specialised b...

Oceanic islands are interesting and somewhat specialised biomes. Islands which have broken away from the main continents have similarity of flora and fauna related to the continent

What is choanocytes, Which one of the following statements about all the fo...

Which one of the following statements about all the four of Spongilla, Leech, Dolphin and Penguin is correct? 1. Penguin is homiothermic while the remaining three are poikilothe

Plant responses to light-dark cycles, Plant Responses to Light-Dark Cycles ...

Plant Responses to Light-Dark Cycles Based on their requirement for day length (number of hours of light) for flowering plants have been grouped under three major categories,

Explain about the amino acids and proteins, Explain about the Amino Acids a...

Explain about the Amino Acids and Proteins? We shall now study the properties of amino acids which we know are the building blocks of proteins.  In this practical, we shall car

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