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.
why obelia is of special interest in zoology
Consistently overwatering a potted tomato pla nt will eventually kill it. Using the map, suggest why waterlogged soil results in plant death. O2 cannot reach respiring root cells.
Disease and Pathogenesis Disease management is a complex and challenging undertaking. Not only are new pathogens and treatments constantly being discovered by effective
Assessment of new born The main purposes are: i) To identify normal characteristics in the neonate ii) To identify existing abnormalities, ii any iii) To carry
How will the plant-incorporated protectants rules change EPA's current registration process? The rules clarify which plant-incorporated protectants are needed to be evaluated u
What is meant by the law of use and disuse and by the law of the transmission of acquired characteristics? As per to the law of use and disuse the characteristics of a body var
differentiate between scanning electron microscope and a transmission electron microscope in terms of their functions
What is Cuticle? The nonliving, and noncellular outer layer of an organism secreted by underlying epidermis. Cuticles are common in a range of animals including nematodes, anne
What is Computerised tomography Computerised tomography (CT, but also known as computerised axial tomography, or CAT) provides structural images. To generate brain scans, low l
Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4
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