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

What is the vector of chagas disease, Q. What is the vector of Chagas' dise...

Q. What is the vector of Chagas' disease? How is the disease transmitted? The vector of the Chagas' disease is its intermediate host, a triatomine bug. The key species is Triat

Explain the uses of hydrocolloids, Explain the uses of hydrocolloids In...

Explain the uses of hydrocolloids In particular, hydrocolloids can provide water for increasing the flexibility (plasticizing) of other food components. These can also affect i

Prolactin - vertebrates, Normal 0 false false false EN-...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Pathophysiology of constrictive pericarditis, Q. Pathophysiology of constri...

Q. Pathophysiology of constrictive pericarditis? Ans. The thickened and rigid pericardium causes constriction of the heart and restricts ventricular dialatation and diasto

Define health effects related to probiotics, Define Health Effects related ...

Define Health Effects related to Probiotics? Several lines of evidence support the conclusion that normal gut microflora are involved in resistance to disease, especially gastr

Stored metabolites - seed and fruit, Stored Metabolites - Seed and Fruit ...

Stored Metabolites - Seed and Fruit In a large majority of seeds food is stored in the cells of the endosperm. In coconut, wheat and castor bean for example, it is the endospe

Explain gonorrhea, Gonorrhea Single doses of cefixime (Suprax) orally ...

Gonorrhea Single doses of cefixime (Suprax) orally or ceftriaxone  (Rocephin)  intramuscularly (IM) are highly effective for uncomplicated anogenital or pharyngeal infection,

Define symptoms in stomach and mouth of pernicious anaemia, Define symptoms...

Define symptoms in Stomach and Mouth of pernicious anaemia? Stomach: The cells which secrete acid and enzymes are atrophied. The gastric secretions are devoid of acid, pepsin

Observation of bumpus, An interesting observation made by an American biolo...

An interesting observation made by an American biologist H.C. Bumpus (1899) provides a good explanation for normalising selection. Bumpus collected some 136 injured house sparrows

Risk factor modification, Risk Factor Modification :  Even after CABG,...

Risk Factor Modification :  Even after CABG, patients are at risk of progression of native coronary artery disease and development of lesions in the conduits. Modification of

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