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

Explain milling extraction rate, Explain Milling extraction rate The ch...

Explain Milling extraction rate The chemical composition of the flour depends on the milling extraction rate.  Increasing the rate of flour extraction decreases the proportion

Absorbing surface of the small intestine is increased, State three ways in ...

State three ways in which the absorbing surface of the small intestine is increased.   The absorbing surface of the small intestine is increased by:- (a) being very long

Asexual reproduction, Which type of asexual reproduction takes place in mon...

Which type of asexual reproduction takes place in monocystis?

Use of toxic amino acids, Q. Explain Use of Toxic amino acids? Lathyru...

Q. Explain Use of Toxic amino acids? Lathyrus sativus (kesari dhal) seeds contain toxic amino acid beta-oxalyl aminoalanine (BOAA), is considered to be responsible

Theory of germplasm, THEOR Y OF GERMPLASM - August Weismann (1834-1...

THEOR Y OF GERMPLASM - August Weismann (1834-1914) criticized the inheritance of acquired characters by putting forward the theory of continuity of germplasm. According

What are some human diseases caused by virus, What are some human diseases ...

What are some human diseases caused by virus and what are their respective modes of transmission? The main viral diseases transmitted by respiratory secretions (cough, sneezes)

Artificial parthenogenesis, Artificial Parthenogenesis In various cas...

Artificial Parthenogenesis In various cases, the eggs that normally develop only after fertilisation can be experimentally induced to develop parthenogenetically by specific

What raw materials require for the manufacture of margarine, What raw mater...

What raw materials require for the manufacture of margarine Soybean and peanut (or groundnut) oils are of great economic importance. Refined soybean oil contains branched fura

What is tuberculosis, What is tuberculosis? How is the disease transmitted?...

What is tuberculosis? How is the disease transmitted? Is there treatment for tuberculosis? Tuberculosis is a disease caused by the Mycobacterium tuberculosis, bacteria which at

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