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

Cut-off points to judge on failures - root canal treatment, Determine cut-o...

Determine cut-off points to judge on failures - Root Canal Treatment a)  Persistent of signs and/or symptom. b)  If in one year there is no decrease in lesion size. c)  I

Hydrocarbons do not readily evaporate at room temperature, The fact that so...

The fact that some pure solutions of hydrocarbons do not readily evaporate at room temperature is a result of- Select one: a. London dispersion forces. b. The hydrophobic

Amelioration of mineral deficiency, Amelioration of mineral deficiency ...

Amelioration of mineral deficiency Performance of livestock in the tropics is mainly governed by the quality and quantity of nutrients provided in the diet. In most of the dev

What is ribosomes , Each  ribosome  having  of two  subunits  a sma...

Each  ribosome  having  of two  subunits  a small  subunit  and  a large  subunit, every of that is a multi component  complex  of rRNAs (ribosomal  RNAs)  and ribosomal proteins t

What is an etiological agent of disease, What is an etiological agent of di...

What is an etiological agent of disease? An etiological agent of disease is the agent that causes the disease. It might be a living being, substance or environmental fact.

Are mollusc metameric beings, Q Are mollusc metameric beings? Exclusively a...

Q Are mollusc metameric beings? Exclusively analyzing this feature could it be said that molluscs are evolutionarily proximal to nematodes or to annelids? In molluscs there is

What is market in management term, What is market in management term? ...

What is market in management term? A market: There is Buyers and sellers for a good or a service come within contact for the function of normally exchange, for money. Lik

What ions must a plant obtain from the soil, What ions must a plant obtain ...

What ions must a plant obtain from the soil in order to make (a) ATP, (b) chlorophyll?   (a) To create ATP (adenosine triphosphate) a plant requires a supply of phosphate io

Define interaction of vitamin c with riboflavin, Define interaction of Vita...

Define interaction of Vitamin C with Riboflavin? The two coenzyme forms of riboflavin are FMN and FAD. They are found in a large number of systems which function in the metabol

Principle for presence of vanaspati and rancidity in ghee, Principle for Pr...

Principle for Presence of Vanaspati and Rancidity in Ghee Cheap edible and nonedible oils like argemone oil, white oil, tea seed oil etc. are used as adulterants in more expens

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