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 membrane permeability, A pure  phospholipid  bilayer with  its  hyd...

A pure  phospholipid  bilayer with  its  hydrophobic  interior,  is permeable  to water and gases such as O2, CO2, N2 and small uncharged  polar molecules such as urea, ethanol, bu

Explain about the pulmonary and respiratory system, Explain about the Pulmo...

Explain about the Pulmonary and Respiratory System? With aging the chest wall becomes stiffer and less compliant and the muscular force of the diaphragm is reduced causing less

Codominance, explain the genotypes for each blood type and how this is an e...

explain the genotypes for each blood type and how this is an example of codominance. Blood type- A, AB, B, 0

Main constituents of the earth''s atmosphere in our time, What are the main...

What are the main constituents of the earth's atmosphere in our time? The present atmosphere of the earth is constituted essentially of molecular nitrogen (N2) and molecular ox

Etiology and clinical features - neurological disorder, Define Etiology and...

Define Etiology and Clinical Features that causes neurological disorder? The cause of this neurological disorder can be mechanical or paralytic. The mechanical cause is primari

Determine the functions of human body system, Determine the function of hum...

Determine the function of human body system Human body has different systems to perform different functions. A system consists of organs to perform a particular set of function

Gene targeting, Gene targeting: There is always a debate on gene integrat...

Gene targeting: There is always a debate on gene integration in to the host animal. It is random gene integration Vs gene targeting. Perhaps most significantly, pro-nuclear in

Health insurance and its interaction with medical market, Normal 0 ...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Why does the recombination frequency of genes vary, Why does the recombinat...

Why does the recombination frequency of genes vary with the distance between them in the chromosome? The farther the distance among the loci of two genes in a chromosome the hi

What is the difference between osmosis and diffusion, What is the differenc...

What is the difference between osmosis and diffusion? Osmosis is the occurrence of movement of solvent particles (in general, water) from a region of lower solute concentration

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