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.
How does the substrate concentration affect the speed of enzymatic reactions? Initially as substrate concentration increases, the speed of the reaction enhances; this happens b
E mb ryonic stem cells (ES): These are pleuripotent cells of early embryo (blastocyst) capable of giving rise to all differentiated cells, including germ line cells. Em
what we the strengths and weaknesses of pangenesis theory
State in brief about the soil horizon A soil horizon may be defined as "a horizontal layer of regolith, approximately parallel to the soil surface, and possessing relatively
Q. What is the constitution of the cartilaginous matrix? The cartilaginous matrix is made of generally collagen type II, collagen fibers, and of proteoglycans, proteins associa
information on some heterotrophic plants
Q. Merits and Demerits of system classification? Merits The merits of this system\are as under: • Careful observation and original description of the genera from living
Q. Illustrate Mitral Stenosis and Pregnancy ? Since mitral stenosis is often seen in young women, it is not uncommon to see young women with pregnancy complicated by mitral ste
Q. Explain Shear Pin Model? Shear Pin Model: In this type, a shearing force is applied using a pin to shear the food Product. We are rupturing the element of the food product b
family ,genus, class order , species of mollusca
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