Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
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.
feature
Reality Theory Developed in the 1960s by Willian glasser, a psychiatrist, reality therapists view human nature in terms of behaviour. They believe that human behaviour i
Define Dietary Goals in Parkinson's Disease? The main goals include: - Maintain desirable weight - Promote absorption of anti- Parkinson's drug levodopa - Lessen swall
Define the Diet for Children? By preschool stage, their routines are set' and dietary choices become more and more firm by the time they are in senior school. Further, there is
The cells lining the inside of the cheek are frequently removed for making observations of basic cell structure. The cells are from stratified squamous epithelium. Explain a reason
explain abt invivo gene therapy ..
Q. Which are the glands present in the epidermis of birds, reptiles and mammals? In the epidermis of reptiles and birds there are practically no glands. In mammals there are se
Explain the Selective Media - Culture Media? It is used to select specific groups of bacteria by favouring the growth of desired bacteria and inhibiting the growth of undesired
Which is the vertebrate class that is considered the first entirely terrestrial? The first totally terrrestrial vertebrate class, totally independent from the aquatic habitat,
Nitrate Uptake Nitrate must enter the cells before undergoing assimilatory reduction by the joint action of nitrate reductase and nitrite reductase. Cells accumulate NO - 3
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!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd