Regional specialisation, Biology

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.

Posted Date: 1/15/2013 2:43:44 AM | Location : United States







Related Discussions:- Regional specialisation, Assignment Help, Ask Question on Regional specialisation, Get Answer, Expert's Help, Regional specialisation Discussions

Write discussion on Regional specialisation
Your posts are moderated
Related Questions
Medtronic Hancock (Standard Model) :  These are gluteraldehyde preserved xenograft aortic valve, which are mounted. The modified orifice version (M-0) is one where the right

Group  specificity Some enzymes prefer a specific functional group to be present\%on  the substrate molecules. Example:- alcohol dehydrogenase  acts on alcohols having  -OH  gr

Title Legal aspects in obstetrical ultrasound  Introduction Obstetric ultrasound is an essential component of antenatal care and it is widely perceived to be associated

Explain the Bioavailability of Vitamin E? For dietary purposes, vitamin E activity is expressed as a-tocopherol equivalents (a-TEs). One α-TE is the activity of l mg α-tocophe

classification of all organisms under d phylum protozoa

Describe Genetic Recombination ? Genetic recombination, which provides the variation necessary for evolution, can occur through a variety of processes during cell reproduction:

The goals of treating heart failure are relief of symptoms, improvement in   exercise tolerance, and reduction in the number of hospitalizations, decreasing morbidity and mortality

Determine the Factors that Influence manganese absorption? Let us now see which factors influence Mn absorption. Major factors which may influence the absorption of this min

why green seeds reappeared in the f2 generation

Q. What are clotting factors? Clotting factors are substances (coenzymes, enzymes, reagents) necessary for the clotting stages to happen. Besides those triggering reagents and