Regional specialisation, Biology

Assignment Help:

Regional Specialisation

Regional specialisation takes place usually by three processes –

1) Restriction of certain structures to a few segments, for example, gonads are restricted to a few specialised genital segments in annelids (e.g. earthworm).

2) Structural divergence of segmental structures to perform different functions. For example some segmental appendages may be modified from those suitable for locomotion to those adapted for grasping or chewing, (e.g. insects)

3) Fusion of segments along the length of the animal. For example, fusion of anterior segments to form the head. The head of Nereis consists of the acron and two other segment while that of Drosophila is composed of five segments.

The second significant feature of metameric segmentation is its importance in the ' locomotion of soft bodied animals. The acoelomates animals use their musculature of longitudinal and circular muscles for locomotion but the evolution of a coelomic cavity has allowed the fluid to act as hydraulic skeleton. In invertebrates like annelids, muscles of the body wall act against this pressure. When circular muscles Contract, hydrostatic pressure on coelomic fluid will result in lengthening of the body; when longitudinal muscles contract, it will result in widening of the body. Since metameric segmentation results in compartmentalisation of the body, this elongation and widening of the body can be restricted to a few segments at a time.

This local change in the shape of the elongate body increases the locomotory efficiency. The broadened part of the body can be firmly fixed against the burrow especially if there are clinging structure such as setae and the lengthening of the body will produce considerable thrust resulting in progression of the animal. Thus the alternate peristaltic waves enable the animal to move forwards faster and efficiently.


Related Discussions:- Regional specialisation

Describe the relation between nutritional and infections, Nutritional and ...

Nutritional and Infections The interaction between nutrition and  infection  is  synergistic -  that is  nutritional deficiency lowers resistance  to infection and infection ag

What do you understand by coelenteron, What do you understand by Coelentero...

What do you understand by Coelenteron? The name given to internal cavity of the cnidarians. This is an incomplete gut with just one opening, the mouth. Food to be digested and

Exchange in alveoli, Exchange in Alveoli The blood that enters the lun...

Exchange in Alveoli The blood that enters the lungs from the heart has been routed through body tissue where mitochondria1 respiration has depleted its oxygen content. It thus

What is gum arabic, Gum Arabic Gum Arabic or Gum Acacia is the oldest  ...

Gum Arabic Gum Arabic or Gum Acacia is the oldest  and best known of the natural gums. Gum Arabic is the natural exudate produced by various species of the thorny Acacia trees

Explain chiasms of homologous chromosomes, Q. What are the "chiasms" of hom...

Q. What are the "chiasms" of homologous chromosomes observe in prophase I? Chiasms are intersections of two tracts in the form of X, The chiasms seen in prophase I are chromoso

How to investigate mitral stenosis by echocardiography, Q. How to Investiga...

Q. How to Investigate mitral stenosis by Echocardiography? Echocardiography is diagnostic in mitral stenosis. There is varying degrees of thickening and calcification of leafle

Explain ribosomes in eukaryotic and in prokaryotic cells, How different are...

How different are the location of ribosomes in eukaryotic and in prokaryotic cells? In prokaryotes ribosomes are create free in cytoplasm. In eukaryotic cells they can also be

Cardiomyocytes and motor neurons, Describe the mechanisms and genetic regul...

Describe the mechanisms and genetic regulations that underpin how two cells such as cardiomyocyte and a motor neuron have identical gnomes, yet are functionally and structurally di

Elimination of the risk factors - diabetes mellitus, Q. Elimination of the ...

Q. Elimination of the risk factors - diabetes mellitus? In other words, in diabetes it refers to maintaining of normal body weight, healthy nutritional practice, regular physic

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