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

Find the net charge of the predominant form asp, Determine the net charge o...

Determine the net charge of the predominant form Asp at (a) pH 1.0, (b) pH 3.0, (c) pH 6.0, and (d) pH 11.0?

Admission procedure - nursing, Admission Procedure   From the time  the...

Admission Procedure   From the time  the child and his family enter the hospital doors, the admission procedure should be carried out in a friendly and efficient manner. Admiss

State about the importance of potassium, State about the importance of Pota...

State about the importance of Potassium  Potassium is the third major element required for plant growth, generally absorbed as K + ion. In soil 95 to 99 percent of potassium e

Types of neurons, TYPE S OF NEURONS - The neurons are classified on th...

TYPE S OF NEURONS - The neurons are classified on the basis of their structure and function. (A) On the basis of the structure, the neurons are of four types.

Disorder of parathyroid function, Disorder of Parathyroid Function: Th...

Disorder of Parathyroid Function: The disorders of parathyroid function may  either  lead  to increased production or decreased production of parathormone.  Hypoparathyroid

Explain subphylum urochordata, Subphylum Urochordata : (13,000 species, se...

Subphylum Urochordata : (13,000 species, sea squirts) Notocord is dorally situated, nerve tube dorsally situated and is hollow, chordate characteristics seen mainly in bilatera

Explain advantages of using yeast as a source of protein, Organism:- Yeast ...

Organism:- Yeast Advantages Large size, hence separation from the culture medium is easy.  As the pH of the growth is towards acidic side, high amount of lysine is prod

Skin and cornea grafting, SKI N GRAFTING - Skin for grafting is taken ...

SKI N GRAFTING - Skin for grafting is taken from another part of body of the same persons. Now it is possible to grow a sheet of skin in culture from a small piece of skin

Why the pancreas is considered a mixed gland, Q. What is a mixed gland? Why...

Q. What is a mixed gland? Why the pancreas is considered a mixed gland? Mixed gland is a gland that produces exocrine and endocrine secretions. The pancreas is an example of

What are living and nonliving reservoirs, What are living and nonliving res...

What are living and nonliving reservoirs? Viruses are both living as well as non-living. They have reservoirs of genes. A one nucleotide is a unit of gene. Viral genes make use

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