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

What is the implant site evaluation, Implant site evaluation 1. Ridge:...

Implant site evaluation 1. Ridge: Total buccolingual width of the ridge- the thickness of the soft tissue ( bucally +lingually)= Buccolingual width of the bone. There shou

Define the management of epileptic patients, Define the Management of Epile...

Define the Management of Epileptic Patients? The primary treatment of epilepsy is anticonvulsant drugs. The focus of nutritional management is a diet, which is appropriate for

Diabetes mellitus in the world, Diabetes Mellitus in the World As per t...

Diabetes Mellitus in the World As per the International Diabetes Federation Directory, in 1994 the global burden of the disease was estimated at 110 million. These cases will i

Neurological assessment of new born, Neurological Assessment The neuro...

Neurological Assessment The neurological assessment is made up of eight neurological criteria which have high, significance with gestational age. (Fig. 3.2) In order to perf

Material - separation of amino acid by paper chromatography, Determine Mate...

Determine Materials for Separation of Amino Acids by Paper Chromatography? Petridishes (200 mm diameter) with lid, Whatman Chromatographic paper, brown paper, 500 ml separating

How to investigate aortic stenosis by echo cardiography, Q. How to investig...

Q. How to investigate aortic stenosis by Echo Cardiography? 2D Echo cardiogram shows the number of cusps. But presence of raphae and distorted anatomy due to calcification may

Explain phylum cyanobacteria, Phylum Cyanobacteria Cyanobacteria  are p...

Phylum Cyanobacteria Cyanobacteria  are prokaryotes,  but  they are not  like bacteria  in  the usual  sense of  the word.  The cyanobacteria  lack chloroplasts,  and  their  l

What is immune memory, How can an organism that once underwent contact with...

How can an organism that once underwent contact with an antigen be immunized against future infections by the same agent? This phenomenon is known as immune memory . When an a

What do you mean by gametogenesis, Q. What is the kind of cell division tha...

Q. What is the kind of cell division that allows sexual reproduction? What is gametogenesis? Meiosis is the kind of cell division that permits sexual reproduction since it redu

Complete test of hypothesis, Conduct a test of hypothesis to verify whether...

Conduct a test of hypothesis to verify whether a difference exists among the average numbers of ant species found at sites in the two regions of Mongolia. Use  .  You will require

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