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

Effect on microbial growth and activity, Effect on Microbial Growth and Act...

Effect on Microbial Growth and Activity Bacteria require higher aw for growth than fungi. Gram-negative bacteria have higher requirements than gram positives. Most spoilage ba

Which cannot react with dehydration reaction, Which of the following pairs ...

Which of the following pairs of functional groups CANNOT react with each other by a dehydration reaction? Select one: a. Carboxyl;Hydroxyl b. Carboxyl;Sulfhydryl c. Pho

What is signifying by concentration gradient, Q What is signifying by conce...

Q What is signifying by concentration gradient? Is it correct or not to refer to "concentration gradient of water"? Concentration gradient is the variation of concentration of

Explain genetically modified organisms, Q. Explain Genetically Modified Org...

Q. Explain Genetically Modified Organisms? Techniques that use gene modification through (a) recombinant DNA technology and (b) cellular techniques of introducing DNA into an o

Determine indicators used in monitoring and surveillance, Determine Indicat...

Determine Indicators used in monitoring and surveillance? Various simple indicators may be used such as: 1) Weight-for-height 2) Body mass index (weight in kg/square of h

Amphibians, Amphibians is the class of terrestrial vertebrates which lay t...

Amphibians is the class of terrestrial vertebrates which lay their eggs (and mate) in water but live on land as adults following the juvenile stage where they live in water and br

Plants - rapidly flowing waters, Plants - Rapidly Flowing Waters Among...

Plants - Rapidly Flowing Waters Among the plants only small, well attached forms, such as sessile algae can survive here. Thus, due to the presence of only a few plants, the n

Which is better to grow plants in rock sand or soil, Which is better to gro...

Which is better to grow plants in Rock sand or soil? When we grew plants inside, with there is no wind, and the plants in the rocks grew improved than the plants that were grow

Explain about the parkinson''s disease, Explain about the Parkinson's disea...

Explain about the Parkinson's disease? Parkinson's disease is a degenerative central nervous system (CNS) condition characterized by progressive loss of cells within substantia

Morphological changes, Morphological changes Regressive changes -Thes...

Morphological changes Regressive changes -These changes include the gradual reduction and ultimate disappearance of all those larval structures or organs that become redundan

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