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

Living matter, LIVING MATTER Since at the subatomic level, all matter i...

LIVING MATTER Since at the subatomic level, all matter is basically similar, the fundamental chemical and physical principles are equally applicable to all objects in nature; y

What else is carried in the plasma, What else is carried in the plasma? ...

What else is carried in the plasma? In addition to proteins, plasma having salts (ions), glucose, lipids and amino acids, hormones, carbon dioxide and urea

Residue in foods, Residue is defined medically as the solid contents that h...

Residue is defined medically as the solid contents that have reached the lower intestine. A low residue diet is composed of foods, which are easily digested and readily absorbed, r

How to reduce the stresses on the implant, How to reduce the stresses on th...

How to reduce the stresses on the implant i) There is need to reduce the stresses on the implant - ii) Frequent recall for maintenance or hygiene appointments. iii) Gingi

Show six bad listening habits, Discuss six bad listening habits. Which do y...

Discuss six bad listening habits. Which do you think is the biggest challenge for you personally?

Determine the interactions among the splicing machinery, Which of the follo...

Which of the following mediates the interactions among the splicing machinery and the mRNA transcript? A. Alpha helical structures within the RNA binding domain of the splicing

Phylum mollusca, what is the correct classification of phylum mollasca

what is the correct classification of phylum mollasca

Do echinoderms have circulatory and respiratory systems, Q. Do echinoderms ...

Q. Do echinoderms have circulatory and respiratory systems? In echinoderms there are not well- defined respiratory with the exception of the holothurian group and circulatory s

Gastrulation, Gastrulation  Gastrulation is the process through whic...

Gastrulation  Gastrulation is the process through which the presumptive areas of organ specific rudimetns present on the surface of blastula move to their specific position

Anaphase, Anaphase This  phase is of shortest duration. It  begins  wit...

Anaphase This  phase is of shortest duration. It  begins  with  a sudden  separation  of the two chromatids of each   due  to splitting   of its centromere and  then a slow mov

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