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!
Syncytial Theory - Metazoa
This theory suggests that the ancestral metazoan was at ,first Syncytial in structure but later became cellularised by formation of cell membranes around individual nuclei this producing a typical multicellular body. Hadzi (1953) and Hanson (1977) have been the chief proponents of this theory. As many ciliates tend to have a bilateral symmetry, the advocates of this theory maintain that the ancestral metazoan was bilaterally symmetrical similar to the present day acoelous flatworms. The theory receives support from the fact that acoelous flatworms are
Figure: Possible routes for evolution of animals
There are several objections to this theory. It ignores the embryology of flatworms in which nothing similar to cellularization occurs, nor does it explain the presence of flagellated sperms in metazoans. Perhaps the most important objection to this theory is that it assumes that .acoelous flatworms are the most primitive metazoans and therefore, presumes bilateral symmetry to be more primitive than radial symmetry and thus radial coelenterates must have been derived from bilateral flatworms. But then it is accepted that radial symmetry is more primitive than bilateral symmetry and radial coelentrates could not have evolved from flatworms.
Gametophytic Incompatibility In GSI systems callose deposition is not evident on the stigma but is very conspicuous in the pollen tube. Sometimes the callose deposition occurs
Chronic Aortic Regurgitation : Several factors have to be taken into account before recommending surgery. These include severity of symptoms and LV function. With evidence o
Q. After digestion the next step is absorption done by cells of the mucous membrane of the intestine. For this task a large absorption surface is an advantage. How is it possible i
What is polyembryony? Polyembryony is the phenomenon in which a single embryo in its initial embryonic stage separates itself forming many new individuals of the similar sex an
Pericardiocentesis : This is usually done by the cardiologist. It is better done with ECG and haemodynamic monitoring. Subxyphoid route is preferred with the patient positio
Q. Why is it not correct to assert that the DNA self- replicates? The DNA is not completely self-sufficient in its duplication process because the replication does not occur wi
How do embryos of placental mammals excrete nitrogen wastes? Placental animals, as well as embryos, excrete urea. In the adult placental mammal urea is excreted by the urine.
Animal Tissue Culture: The term tissue culture refers to the culture of all organs, tissue fragments and dispersed cells on a suitable nutrient medium. It may be divided into
There are 5 distinct yet constantly interacting phases in the care process. Assessment : A broad base of relative information about the patient's nutritional status, food ha
Reparative Regeneration This type of regeneration, as the name suggests, involves repair of a wound or replacement of a body part removed intentionally or because of injury.
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