Origin and evolution of metazoa, Biology

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.

Posted Date: 1/15/2013 2:48:27 AM | Location : United States







Related Discussions:- Origin and evolution of metazoa, Assignment Help, Ask Question on Origin and evolution of metazoa, Get Answer, Expert's Help, Origin and evolution of metazoa Discussions

Write discussion on Origin and evolution of metazoa
Your posts are moderated
Related Questions
Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4

Long buccal nerve The long buccal nerve is a branch of the mandibular division of the trigeminal nerve which provides sensory innervation to the buccal gingiva and mucosa of th

Green leaves make food for plants Heat some alcohol in a jar over boiling water unless it boils. Break various green leaves from a geranium or other plant which has been in the

Define the symptoms in Bone marrow of pernicious anaemia? The nucleated red cells of the marrow are greatly increased.  The successive nucleated cell stages in erythropoiesis a

compare and contrast the structure of the following: hyrda plain, hydra mematocysts, obelia, amoeba, euglena, paramecium caudatum conjugation, euglena acus.

Electron acceptor is a molecule which forms the part of the electron transport system which transfers electrons ejected by chlorophyll during the process of photosynthesis. Part o

What are the major plant tissues that form the rings observed on stem sections of some trees? The rings observed on a stem cross section of the dicot trees are made of conducti

In radially symmetric animals there is no posterior, or anterior, right sides to the animal. Rather we refer to two sides of the animal by referring to the location of the mouth. I

a) A cat has just arrived to the veterinary clinic with low blood pressure. The cat weighs 5 kg, and as the on call Vet you want to use a bag of saline to prepare a dopamine drip f

Energy Cycle  of Living Being Source of energy :All  matter  locks  energy in the  from of   bonds  between component  molecules and   atoms. This  energy is the chemical  ener