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.
EXPLAIN THE CONSTITUENT OF FOOD GROUPS AND THEIR SOURCES
Overturn - Thermal stratification The summer or winter stratification is seasonal. Circulation of lake water occurs twice a year, in the spring and autumn (fall) seasons by a
What are the functions of the spleen? Why is a total splenectomy (surgical removal of the spleen) compatible with life? The spleen has many functions: it participates in the de
A complete motor neuron is removed from a frog and placed in a large volume of normal physiological saline. The neuron is healthy; it has a stable resting voltage of -70 millivolt
What are cilia and flagella? Cilia and flagella are structures found in prokaryotes as well in eukaryotic cells. They play defense, nutrition and movement roles for the cell. I
What are the typical vegetation and the typical fauna of the temperate forests? In the temperate forest deciduous trees predominate. Various Mammals are found in great number,
My friend was injured several years ago in a car accident and she was diagnosed with a herniated disc. Can you please explain using the correct anatomical terminology what herniati
When the work sheet is finished all the essential information to prepare the statement of retained earnings, income statement and balance sheet is readily available. Currently you
Explain some important phospholipids The chemical structure of phosphatidylcholine (lecithin) illustrated here in Figure is typical of the phosphatides found in the brai
Is it possible to perform investigation of natural paternity, maternity or brotherhood and sisterhood using the ABO blood typing? By using an ABO blood typing it is possible on
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