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

ASSINMENT, HISTORY ON CLASSIFICATION IN BIOLOGY

HISTORY ON CLASSIFICATION IN BIOLOGY

What are the cells that produce the myelin sheath, Q. What are the cells th...

Q. What are the cells that produce the myelin sheath? Of which substance is the myelin sheath formed? In the central nervous system (CNS) the myelin sheath is made by appositio

What are the nucleic acids, Q. What are the nucleic acids? What is the hist...

Q. What are the nucleic acids? What is the historic origin of this name? RNA and DNA, the nucleic acids, are the molecules responsible for the hereditary information that comma

Write the definition of counselling, Q. Write the definition of counselling...

Q. Write the definition of counselling? The counselling process, involves various steps in a sequence as given below: 1. Rapport-Building 2. Locating the Problem 4. Pl

Post-operative care of cardiac surgical patients, POST-OPERATIVE CARE OF PA...

POST-OPERATIVE CARE OF PATIENTS The first few days following cardiac operations are the most critical in terms of the patient's survival. The safety with which a patient can

Determine the greater palatine nerve and vessel, Greater Palatine nerve and...

Greater Palatine nerve and vessel  The greater palatine nerve runs forward in a groove on the inferior surface of the hard palate to communicate with nasopalatine nerve in inci

Cell theory, Cell Theory The term cell was first used by an English cyt...

Cell Theory The term cell was first used by an English cytologist, Robert Hooke (1665) not for unit protoplasmic masses, but for the well defined and empty compartments, he obs

Animal kingdom, what is animal kingdom and what are its functions

what is animal kingdom and what are its functions

Explain the serial dilution process - plate counts, Explain the Serial Dilu...

Explain the Serial Dilution Process - Plate Counts? Dilution factor is the reciprocal of the dilution used. As number of microorganisms in original sample is not known, the ori

What physical fitness tests examine, What Physical fitness tests examine? ...

What Physical fitness tests examine? Physical fitness tests examine the components of physical fitness such as endurance, speed, strength, flexibility and body composition. 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