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

How do taenias obtain food and make gas exchange, How do taenias obtain foo...

How do taenias obtain food and make gas exchange? Tapeworms have hooks and sucking structures on their heads (scolex) that fixate the parasite in the gut wall; these structures

Lateral and the apical buds of the plants, What is the dissimilarity betwee...

What is the dissimilarity between the lateral and the apical buds of the plants? The Lateral buds are portions of meristematic tissue located in the base of the shoots. The Api

Relate the oxide layer and biocompatibility of titanium, Q. Relate the oxid...

Q. Relate the oxide layer and biocompatibility of titanium? The compatibility of a metal with its host environment depends on its resistance to biodegradation and on the degree

Drawbacks of lamellar model, Drawbacks of Lamellar model This model ...

Drawbacks of Lamellar model This model does not explain the elasticity of PM. Although this model says that PM is elastic but it also states that head of lipid molecules is

Explain the use of benzoates acid, Q. Explain the use of Benzoates acid? ...

Q. Explain the use of Benzoates acid? Benzoic acid, sodium benzoate and the parahydroxy esters (parabens) are used as preservatives. Benzoic acid and its sodium salt, sodium be

Explain fungi - nutritional types of microorganisms, Explain Fungi - Nutrit...

Explain Fungi - Nutritional Types of Microorganisms? Fungi are filamentous, eukaryotic microorganisms, ubiquitous in nature. These grow best in dark and moist habitats. Their h

What are some evolutionary advantages of animals, What are some evolutionar...

What are some evolutionary advantages of animals with complete digestive tube? The complete digestive tube permits animals to continuously feed themselves without waiting for r

Describe aerobic respiration in krebs cycle, Q. Until the Krebs cycle, aero...

Q. Until the Krebs cycle, aerobic respiration can be described without mentioning oxygen, the chemical element after which the reaction gets its name. Where in the process does thi

How does the synthetic theory of evolution explain this fact, In hospitals ...

In hospitals where many tuberculosis patients are treated the population of the tuberculosis mycobacteria may be constituted of multiresistant (to antibiotics) strains. How does th

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