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

Water adaptations, Water Adaptations After becoming familiar with the t...

Water Adaptations After becoming familiar with the two kinds of water stresses you would like to know about the adaptations in plants and animals which enable them to survive u

Obelia, what are the economic importance of obelia?

what are the economic importance of obelia?

Elaborates congenital aortic stenosis in details, Elaborates Congenital Aor...

Elaborates Congenital Aortic Stenosis in details? More common in males (4: 1). High incidence of Bicuspid Aortic valve. Murmur present from early infancy and sometimes at birth

Importance of care in children, Importance of care in children Childre...

Importance of care in children Children  are not  just  small adults. This is important  to keep  in mind when evaluating how children react to illness, perceive an illness, o

Reproductive isolation, REPRODUCTIV E ISOLATION - According to the bio...

REPRODUCTIV E ISOLATION - According to the biological species concept, members of one species are reproductively isolated from members of all other species. Accordingly, re

Define the sterilization protocol, Define the Sterilization protocol? S...

Define the Sterilization protocol? Sterilization protocol encompasses the following: 1. Transport of instruments to the sterilization area 2. Cleaning of instruments 3

Explain the interaction of vitamin a with zinc, Explain the interaction of ...

Explain the interaction of vitamin a with Zinc? Its deficiency interferes with vitamin A metabolism. It leads to a reduction in the synthesis of plasma proteins, particularly,

Disorders of male reproductive system, DISORDER S OF MALE REPRODUCTIVE SYS...

DISORDER S OF MALE REPRODUCTIVE SYSTEM (i) Prostatomegaly - Enlargment of prostate gland. It causes difficult & painful micturition. (ii) Impotence - Inability of male

How you would accomplish cloning using of numbered steps, A restriction map...

A restriction map of plasmid and a human gene of identified sequence is demonstrated below. Your job is to clone the human liver cDNA for that gene than the start codon is closer t

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