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

Carbohydrates requirement during myocardial infarction, Q. Carbohydrates re...

Q. Carbohydrates requirement during myocardial infarction? The protein intake generally remains the same as per the RDI i.e. 1.0 gm protein per kg body weight per day. Adequate

ALGAE., HOW ARE THE ORIGIN AND EVOLUTION OF ALGAE..

HOW ARE THE ORIGIN AND EVOLUTION OF ALGAE..

Describe what is respiration in dynamic auscultation, Describe what is Resp...

Describe what is Respiration in Dynamic Auscultation ? a) S 2 : Splitting of S 1 is audible during inspiration. b) Diastolic sounds and Ejection sounds: Inspiration augment

Seed coat effects, Seed Coat Effects In some seeds dormancy is impose...

Seed Coat Effects In some seeds dormancy is imposed by the presence of the seed coat; if this is removed, the seed germinates. Two possible types of mechanisms could be invol

What is the objectives of genesis of coronary artery disease, What is the o...

What is the objective of genesis of coronary artery diseases and risk factors ? After reading this unit, you should be able to: Understand the genesis of CAD; 1 learns about th

Nervous system control of blood pressure, Q. Nervous System control of bloo...

Q. Nervous System control of blood pressure? Most nervous controls are achieved via involuntary reflex arcs involving pressoreceptors, the vasomotor centers of the medulla, and

What is law or theory of demand state, What is law or theory of demand stat...

What is law or theory of demand state? The law or theory of demand states as consumers we derive satisfaction or ‘utility’ like a result of consuming a good or a service. It va

Explain marine oils, Marine oils These oils typically contain large amo...

Marine oils These oils typically contain large amounts of long - chain omega-3-polyunsaturated fatty acids, with up to six double bonds and they are usually rich in vitamins A

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