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

Biodeterioration, is paper broken down by microorganisms

is paper broken down by microorganisms

What is active site, What is Active site Active site : The site on  ...

What is Active site Active site : The site on  the surface of an enzyme to which  substrate or substrates bind.

Explain the bright field microscopes, Explain the Bright Field Microscopes?...

Explain the Bright Field Microscopes? Figure illustrates the compound bright field microscope. This is the most commonly used microscope in biology and microbiology courses. It

Ammonia assimilation, Ammonia Assimilation - Inorganic Nitrogen and Sulphur...

Ammonia Assimilation - Inorganic Nitrogen and Sulphur Metabolism Nitrogen (N 2 ) gas and NO 3 are the most common available forms of inorganic nitrogen. Both are enzymaticall

Define counseling and compliance for celiac disease, Define Counseling and ...

Define Counseling and compliance for celiac disease? If symptoms do not improve, the child's diet should be reviewed and evaluated. A decrease in diarrhoea, increase in height

Explain carboxymethyl cellulose, Carboxymethyl Cellulose (CMC) CMC is a...

Carboxymethyl Cellulose (CMC) CMC is a linear, long-chain, water-soluble, anionic modified polysaccharide. It is a derivative of cellulose formed by its reaction with alkali an

Fibroblast, Fibroblast  is the term applied to a cell of connective tissue ...

Fibroblast  is the term applied to a cell of connective tissue which is separated from similar cells by some degree of the matrix material; fibroblasts secrete elastin and collagen

Is a viral infection treated with drug, Q. Is a viral infection treated wit...

Q. Is a viral infection treated with the same kind of drug that treats bacterial infections? The Antibacterial drugs, potent against a great variety of bacteria, are not effect

Define vapor-pressure lowering and osmotic pressure, Define Vapor-pressure ...

Define Vapor-pressure lowering and Osmotic pressure? 1. Vapor-pressure lowering: the decrease in the vapor pressure of a solution containing nonvolatile solutes, compared to th

Pleural biopsy, Pleural Biopsy Pleural biopsy is one of the diagnostic...

Pleural Biopsy Pleural biopsy is one of the diagnostic procedure which may  cause lot of anxiety in  the patient. Procedure Pleural biopsies may be preformed surg

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