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

Skeletal muscle need an antagonistic partner, Why does each skeletal muscle...

Why does each skeletal muscle need an antagonistic partner? Because muscles can only contract and relax, each skeletal muscle requires an antagonistic partner to extend it afte

Agriculture, what''s a mature female sheep called

what''s a mature female sheep called

Can you explain about ventriculography, Q. Can you explain about Ventriculo...

Q. Can you explain about Ventriculography? Cardiac ventriculography is a diagnostic test, i.e., used to define the anatomy and function of the ventricles (left and right) and r

Explain about platyhelminth phylum, What are the best known representatives...

What are the best known representatives of the platyhelminth phylum? The most popular representatives of the platyhelminthes are worms that cause human diseases, like taenia an

Factors associated with accident, Factors Associated With Accident Co...

Factors Associated With Accident Cost in Administrative Functions Loss of prestige. Costs for notification, investigation and legal action. Loss of pu

Determine nutritional requirements in hot environments, Determine Nutrition...

Determine Nutritional Requirements in Hot Environments? Hot environments may be of two types: dry hot, as in the case of deserts or hot and humid in tropical rain forests and c

To study the structure of a seed, To study the structure of a seed Soak...

To study the structure of a seed Soak seeds of bean, pea, pumpkin, sunflower, corn and other large forms. Take away the seed- coats and carefully cut the seeds open. Discover t

Taxonomy, classification of grantia

classification of grantia

Which are the respiratory muscles in mammals, Q. Which are the respiratory ...

Q. Which are the respiratory muscles in mammals? In mammals the muscles that participate in the breathing process are the diaphragm and the intercostal muscles, in respiratory

Transport of substances done across the bryophyte tissues, Q. How is the tr...

Q. How is the transport of substances done across the bryophyte tissues? How is this feature related to the general size of these plants? In bryophytes there are no nutrient-co

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