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

Organogenesis - plant tissue and organ culture, Organogenesis - Plant Tissu...

Organogenesis - Plant Tissue and Organ Culture Organogenesis refers to the differentiation of organs such as roots, shoots or flowers. Shoot bud differentiation may occur dire

Define high density lipoproteins, Q. Define High Density Lipoproteins ? ...

Q. Define High Density Lipoproteins ? High density lipoproteins (HDL) are the smallest of the lipoprotein species and transport approximately 20 to 30 per cent of plasma choles

Biostatics, Biostatics :  This is the application of mathematics in living ...

Biostatics :  This is the application of mathematics in living organisms. Biostatistics is a contraction of biology or statistics sometimes it is called as biometry or biometrics.

Theories to explain fine structure of chromosome, THEORIES TO EXPLAIN FINE ...

THEORIES TO EXPLAIN FINE STRUCTURE OF CHROMOSOME (1 ) Multistranded theory Steffenson 1959 - each chromosome composed of two chromatids (Half Chromosome) and each chromat

Digitalis toxicity, Symptoms of digitalis toxicity include anorexia, nausea...

Symptoms of digitalis toxicity include anorexia, nausea, headache, blurring or yellowing of vision, and disorientation. Cardiac toxicity may take the form of atrioventricular condu

Explain the salient feature of genetic code, The one aspect which is not a ...

The one aspect which is not a salient feature of genetic code, is its being: 1. Degenerate 2. Ambiguous 3. Universal 4. Specific Ambiguous

Respiratory care on admission of patient, Respiratory Care on Admission (Fi...

Respiratory Care on Admission (First two hours) Patient is incubated and ventilator-dependent.  Monitor blood gases hourly and take corrective action immediately.

Biosynthesis of hemes and chlorophylls, In animals, some of bacteria and fu...

In animals, some of bacteria and fungi, and the first step in tetrapyrrole synthesis is the condensation of the amino acid glycine with succinyl  CoA (an intermediate  of the citri

Breast cancer, Breast Cancer Normal 0 false false ...

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

Multiple membrane-spanning proteins, Various integral proteins have multipl...

Various integral proteins have multiple membrane-spanning   -helices. Bacteriorhodopsin, a protein found in a photosynthetic bacterium captures the energy from light and uses it to

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