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

Pathophysiology of acute glomerulonephritis, Pathophysiology   The exac...

Pathophysiology   The exact mechanism of glomerulonephritis  is still under investigation. The dies'ease is characterised by deposition  of immune complexes  consisting of anti

Bomb calorimeter, Normal 0 false false false EN-IN X-...

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

Psychedelic drugs (hallucinogens), PSYCHEDELI C DRUGS (HALLUCINOGENS) - ...

PSYCHEDELI C DRUGS (HALLUCINOGENS) - They act mainly on CNS and greatly alter one's thoughts, feelings and perceptions, called psychedelic drugs. They cause optical or a

Equine herpes virus infections , Equine herpes virus infections (equine rhi...

Equine herpes virus infections (equine rhinopneumonitis, abortions) Equine herpes virus infections in horses and foal are caused by Alphaherpes virus of herpesviridae family p

Find which two amino acids make up this pocket, Sickling occurs in deoxyhem...

Sickling occurs in deoxyhemoglobin, but not in oxyhemoglobin. Normal deoxyhemoglobin (HbA and HbS) molecules have a small hydrophobic "pocket" on the surface of a ? chain. In oxyhe

Explain the composition of nutrient agar and nutrient broth, Explain the Co...

Explain the Composition of Nutrient Agar and Nutrient Broth? The composition and procedure for preparation of some commonly used media, which we will use in the laboratory for

What are the phases to atherosclerosis, Q. What are the phases to atheroscl...

Q. What are the phases to atherosclerosis? There are five phases to atherosclerosis: Phase I: Asymptomaticphase, consists of fatly streaks which are non-obstructive, lipi

Types of cell wall, TYPES OF CELL WALL Cell wall differentiated into th...

TYPES OF CELL WALL Cell wall differentiated into the following layers : 1. Primary Cell Wall       2. Secondary Cell wall             3. Tertiary Cell wall 1 .

Function of adenosine in brain, Q. Function of Adenosine in brain? Aden...

Q. Function of Adenosine in brain? Adenosine has four different receptor subtypes (A1, A2A, A2B and A3). Adenosine A2A receptors are concentrated in striatum. Adenosine recepto

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