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 immediate preoperative period during surgery, Define Immediate Preop...

Define Immediate Preoperative Period during Surgery? Nothing should be given by mouth for at least 8 hours before a general surgery so that the stomach has no leftover food at

Write the meaning of hyperglycemia, Q. Write the meaning of Hyperglycemia? ...

Q. Write the meaning of Hyperglycemia? Hyperglycemia is a Greek term: hyper -meaning excessive; glyc - meaning sweet; and emia- means "of the blood". It is a condition in whic

Briefly explain what is the leaf, Briefly explain what is The Leaf? In a ...

Briefly explain what is The Leaf? In a typical dicot, leaf primordia arise from the apical meristem, which is housed within the terminal bud on a shoot. The leaf cells are produc

How vitamin e is directly related to vitamins a, How vitamin e is directly ...

How vitamin e is directly related to Vitamins A, D and K? A high intake of vitamin E interferes with the functions of other fat-soluble vitamins such as vitamin K absorpt

Study of human age pyramids, Q. What are the analyses provided by the study...

Q. What are the analyses provided by the study of human age pyramids? The study of human age pyramids able to provide the following analyses, proportion of individuals at an ec

Illustrate about sterilization protocol, Q. Illustrate about Sterilization ...

Q. Illustrate about Sterilization protocol? Sterilization protocol includes proper transportation and cleaning of instruments followed by their packing. Items can be sterilized

Define the recommended dietary allowance for thiamin (rda), Define the Reco...

Define the Recommended Dietary Allowance for Thiamin (RDA)? Thiamin, as it must be clear by now, is needed mainly for the metabolism of carbohydrate, branch-chained amino aci

Surgery and prosthetic phase of implant therapy, Surgery and Prosthetic Pha...

Surgery and Prosthetic Phase  Implants are uncovered  Impression recorded  Abutment placed  Provisional prosthesis followed by Definitive prosthesis

Define the role of vitamin a in immune response, Define the Role of Vitamin...

Define the Role of Vitamin A in immune response? Vitamins A is essential to normal immune function and- regulation. As discussed above, during vitamin A deficiency the goblet c

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