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

Explain surface area of lipid oxidation, Surface area The rate of oxida...

Surface area The rate of oxidation increases in direct proportion to the surface area of the lipid exposed to air. Furthermore, as surface - volume ratio is increased; a given

Reproduction, when pollen tube enters the embryo-sac,it has;

when pollen tube enters the embryo-sac,it has;

Ecology, what is the importance to study the tolerance range in real-life...

what is the importance to study the tolerance range in real-life situations?

What is signifying by binomial nomenclature, Q What is signifying by binomi...

Q What is signifying by binomial nomenclature and what are its basic rules? Scientific nomenclature of a species must have at least two names one that classifies it as genus an

Characteristics of female''s skeleton, CHARACTERISTICS OF FEMALE'S SKELETON...

CHARACTERISTICS OF FEMALE'S SKELETON - 1.      Skull is lighter. 2.      Shoulders are nanow. 3.      Sacrum is shorter but wider. 4.      Pelvis is wider. 5.

Explain successive trophic levels in the pyramid of energy, What would occu...

What would occur to the successive trophic levels in the pyramid of energy if the rate of reproduction of phytoplankton was slowed down? Suggest two factors, which could cause l

How does the cd4 counting act to monitor the hiv infection, Q. How does the...

Q. How does the CD4 counting act to monitor the HIV infection? What is another laboratory method to follow up the disease? The CD4 counting test is complete from a blood sample

What are living and nonliving reservoirs, What are living and nonliving res...

What are living and nonliving reservoirs? Viruses are both living as well as non-living. They have reservoirs of genes. A one nucleotide is a unit of gene. Viral genes make use

Explain voriconazole, Explain Voriconazole It has a spectrum of activit...

Explain Voriconazole It has a spectrum of activity similar  to itraconazole but appears to be more active against Aspergillus spp. And some species of  Candida, containing  C.

Explain restriction endonucleases are enzymes, Restriction endonucleases ar...

Restriction endonucleases are enzymes which: 1. make cuts at specific positions within the DNA molecule 2. recognize a specific nucleotide sequence for binding of DNA ligase

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