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

Explain about vitamin k, Vitamin K (Menadione - Vitamin K3, oil soluble) ...

Vitamin K (Menadione - Vitamin K3, oil soluble) Menadione is a yellow, lustrous, crystalline powder. It is easily soluble in benzene, soluble in fats and fatty oils.  It is spa

Describe the term - ambulacral groove, Describe the term - Ambulacral groov...

Describe the term - Ambulacral groove The groove that runs down the oral surface of each echinoderm arm and contain the tube feet. If the region contains a visible furrow, or gr

Dispersal of seeds , Dispersal of Seeds A plant usually bears many fr...

Dispersal of Seeds A plant usually bears many fruits and innumerable seeds. If all the seeds produced by a plant were to germinate in the immediate vicinity, this will have s

Define the functions of vitamin e, Define the Functions of Vitamin E? V...

Define the Functions of Vitamin E? Vitamin E is the major lipid-soluble antioxidant in the cell antioxidant defence system and is exclusively obtained from the diet. The main r

Telophase, Telophase This is the final stage of mitosis  in which the m...

Telophase This is the final stage of mitosis  in which the mitotic  spindle  disappears  and  each polar  chromosomal group is reconstituted  into a daughter  nucleus,  A   nuc

Define contractile protein - biological functions of protein, Define Contra...

Define Contractile Protein - biological functions of protein? These proteins take part in contractile processes like muscle proteins also those found in other cells and tissues

Define nutritional management of eating disorders, Define Nutritional Manag...

Define Nutritional Management of Eating Disorders? In the last unit, we focused on weight management. It is important to understand that the problems associated with too much d

What is the process of breathing, What is the process of Breathing? Oxy...

What is the process of Breathing? Oxygen is supplied to the blood, and carbon dioxide is removed from the blood by the process known as breathing. Air is moved into an exchan

The red data book, The Red Data Book Species judged as threatened are ...

The Red Data Book Species judged as threatened are listed by various agencies as well as by some private organisations. The most cited of these lists is the Red Data Book. It

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