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

Determine the proecss of contrast sense, Contrast sense Sense of contr...

Contrast sense Sense of contrast is the ability to perceive slight changes in luminance between regions which are not separated by definite borders. This is as important as to

Mammalian lungs - respiration, Mammalian Lungs - Respiration In this w...

Mammalian Lungs - Respiration In this we will study mainly mammalian lungs as it is the best representative of a respiratory surface adapted for terrestrial respiration. For t

Define about the absorption of iron, Define about the Absorption of Iron? ...

Define about the Absorption of Iron? Before it can be absorbed, iron whether it is in the form of haem or non-haem must be released from the food matrices where it is bond with

What are the degenerative diseases of the nervous system, Q. What are the m...

Q. What are the main degenerative diseases of the nervous system? The major degenerative diseases of the nervous system are Alzheimer's disease and Parkinson's disease. The

Different blood groups in man, Different blood groups in man 1.Blood Gr...

Different blood groups in man 1.Blood Group "A": Persons having this blood group will have antigen "A' on their red blood cells and antibody "B" in their plasma. 2. Blood Gr

Pulmonary function tests - diagnostic tests, Pulmonary  Function Test: ...

Pulmonary  Function Test: Pulmonary functions  tests (PFTs) provide information about a clients manifestation by measuring lung volumes, lung mechanics, and diffusion capabili

BiologicaL METHODS.., GIVE THE SHORT DETAIL OF HE BIOLOGICAL METHODS

GIVE THE SHORT DETAIL OF HE BIOLOGICAL METHODS

Explain about the prebiotics, Explain about the Prebiotics? Ingredients...

Explain about the Prebiotics? Ingredients/compounds that have a beneficial effect on microflora in the large intestine of the host e.g. fibre, fructo oligosaccharides, lactulos

Loop of henle, Normal 0 false false false EN-IN X-NON...

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

Determine the importance of calcium in soils, Determine the importance of C...

Determine the importance of Calcium in soils Calcium in soils is usually abundant except in acid soils, which occur in humid areas due to excessive leaching. Deficiency of calc

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