Origin and evolution of metazoa, Biology

Assignment Help:

Origin and Evolution of Metazoa

Most of the early metazoans were soft bodied and so their fossils are rare. The extremely fragmented fossil record does not shed any specific light on their origin. Therefore, 'most of the explanations on their origin are based on their embryology and -comparative morphology. A series of theories have been put forward to explain the origin of multicellular metazoans from unicellular organisms. Of these, three principal theories could be considered.

1) Syncytial Theory: That the ancestral metazoans have arisen from a multinucleate. ciliate by compartmentalization or cellularization.

2) Colonial Theory: That the ancestral metazoans have arisen from colonial flagellates by cellular specialisation and interdependency.

3) Polyphyletic Theory: That the metazoans have arisen from more than one group of organisms.


Related Discussions:- Origin and evolution of metazoa

Explain some guidelines to help in use drugs wisely, Explain some Guideline...

Explain some Guidelines to Help in Use Drugs Wisely? By now, you are aware that the interaction of foods and drugs is a complex problem. Researchers cannot always predict wheth

Endodontics principles and practice, Endodontics principles and practice ...

Endodontics principles and practice According to American association of endodontic, retreatment defined as:A procedure to remove root canal filling materials from the tooth vi

Muromonab cd-3 , Muromonab CD-3 (Orthoclone, OKT-3) A monoclonal anti...

Muromonab CD-3 (Orthoclone, OKT-3) A monoclonal antibody against mature T lymphocytes, OKT-3 is primarily used to treat acute rejection episode. IV for 10-14 days. Effe

Parasitic diseases - fascioliasis, P a r a s i t i c Diseases ...

P a r a s i t i c Diseases F a s cioliasis It is a liverfluke infestation characterized by hepatic insufficiency, bile duct obstruction, and poor production per

Interpretation of blood or serum nutrient value in pregnancy, Define Interp...

Define Interpretation of blood or serum nutrient values in pregnancy? Interpretation of blood/serum nutrient values in pregnancy is therefore complex compared to the non-pregn

Biochemistry, tertiary structure of protein

tertiary structure of protein

Jaundice (icterus), Jaundice (Icterus) Jaundice is classified as pre-he...

Jaundice (Icterus) Jaundice is classified as pre-hepatic (hemolytic), hepatic and post-hepatic (obstructive) depending on origin of the problem, and is characterized by yellowi

How different are fecundation in osteichthyes, How different are fecundatio...

How different are fecundation in osteichthyes and in chondrichthyes? In chondrichthyes fecundation is internal by means of copulation. In osteichthyes fecundation generally is

What is the etiological agent of visceral leishmaniasis, Q. What is the eti...

Q. What is the etiological agent of visceral leishmaniasis? How the disease transmitted and what is are its typical manifestations? The Visceral leishmaniasis is caused by the

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

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!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd