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
Complete Metamorphosis In all Endopterygota insects, where wings and other structures develop internally, (in invaginate imaginal epidermal pockets) such as beetles, wasps, b

Process of Respiration Respiratory and Circulator System Gaseous exchange that is intake of oxygen and output of carbon dioxide, takes place at the respiratory surface since

Specify the things needed for a nurse-led primary health care practice relating to childhood obesity. In particular, you need to do the following two things: (a) Indicate:

Endosperm with Micropylar and Chalazal Haustoria Some plants develop haustoria from both micropylar and chalazal ends of endosperm. In Nemophila aggressive haustoria arise fr

Heliozoans - Protozoan Heliozoans are spherical protozoan that occur in the sea or in still bodies of fresh water. They are mainly located in the bottom debris. Fine needle li

Define about the Fusarium - Identification of Fungi and Yeasts? Classification Kingdom - Mycetae Division - Amastigomycotina Subdivision - Deuteromycotina Class - D

What are likely to be the limiting factors in a population of (a) green plants, (b) birds?  (a) In green plants the limiting factors are likely to be light, water, minerals, te

The Peripheral membrane proteins are less strongly bound to the lipid bilayer than integral   membrane   proteins   and can be readily   erased   through washing   the membranes wi

Anaplerotic Reactions Anaplerotic  reactions are  reactions  that  replenish the  intermediates of  citric acid cycle. The  special  enzymatic mechanisms  by  which  the  pool

What is L forms of bacteria?