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

Define food components other than essential nutrients, Define Food Componen...

Define Food Components Other Than Essential Nutrients? In the previous units so far, we have read about the six major nutrients, which are essential for us. Though these vary i

Determine food sources for zinc, Determine Food Sources of Zinc? Zinc i...

Determine Food Sources of Zinc? Zinc is normally associated with the protein and/or nucleic acid fraction of foods. Thus, foods high in proteins are good sources of zinc. Lean

What is mass transportation across the cell membrane, Mass transportation i...

Mass transportation is the access or the exiting of substances in or from the cell engulfed by portions of membrane. The fusion of internal substance-having membranous vesicles wit

What is deletion of cell, What is Deletion of cell? A deletion is simpl...

What is Deletion of cell? A deletion is simply when a tip or fragment of a chromosome breaks off and fails to reattach itself to the chromosome from which it came. The gene, or

What are cytokines, What are Cytokines? Cytokines are polypeptides, whi...

What are Cytokines? Cytokines are polypeptides, which influence the proliferation, differentiation, metabolism and activation of cells. There are three areas in cancer that hav

How does the female gamete move from the ovary to the uterus, Q. How does t...

Q. How does the female gamete move from the ovary to the uterus? The female gamete released from the ovary falls into the surrounding abdominal cavity and is collected by the F

Explain the procedure of balloon pulmonary valvuloplasty, Q. Explain the pr...

Q. Explain the procedure of Balloon Pulmonary Valvuloplasty? Right heart study is done to measure the transvalvular gradient and exclude supravalvular and subvalvular component

Interspecific competition and intraspecific competition, What is the distin...

What is the distinction between interspecific competition and intraspecific competition? Interspecific competition takes place among organisms of the similar species. Intras

What is tree girdling, What is tree girdling? What happens to a plant when ...

What is tree girdling? What happens to a plant when that girdle is removed from the stem (below the branches)? Malpighi's girdling, or tree girdling, is the removal from a ste

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