Origin and evolution of metazoa, Biology

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.

Posted Date: 1/15/2013 2:48:27 AM | Location : United States







Related Discussions:- Origin and evolution of metazoa, Assignment Help, Ask Question on Origin and evolution of metazoa, Get Answer, Expert's Help, Origin and evolution of metazoa Discussions

Write discussion on Origin and evolution of metazoa
Your posts are moderated
Related Questions
V AGIN A - Median, elastic, muscular tube 7.5 cm long. Open into vestibule by vaginal orffice. The lining forms vaginal rugae. Space between vaginal wall & cervix is forn

How many asymmetric carbons does the amino acid serine have? Please explain with a strucutral diagram if possible.

Yesterday, when Eric returned home from jogging, he was breathing heavily, sweating profusely, and complained that his legs ached and felt weak. He took a drink of Gatorade and too

Morphogenesis of an Ectodermal Derivative During the development of vertebrate body the dissimilar regions in the three germ layers of the gastrula become segregated from each

PHYSICAL LAYOUT In this section we shall focus on location floor plan, ventilation, lighting environmental temperature and humidity, acoustic characteristic, communication sy

Explain about the Microcolony DEFT? It allows determination of viable cells. Food homogenate is filtered through a DEFT membrane and then placed on the surface of appropriate c

What is competition? Which type of ecological interaction is competition? Competition is the ecological interaction in which the individuals explore the similar ecological nich

What is the etiological agent of amebiasis? How is it transmitted and what are the typical manifestations of the disease? Amebiasis is caused by the protozoan Entamoeba histoly

Define the Dietary Sources and Chemical Forms? Isoflavones and coumestans are the most common compounds. Soybeans and soyfoods are the most important sources, containing approx

Pressure calculation made using the Bernoulli equation may be used  in conjunction with pressure measurements made by other modalities to determine various intracardiac pressure.