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

Explain kingdom animalia, Kingdom Animalia Multicellular, heterotrophic, ...

Kingdom Animalia Multicellular, heterotrophic, eukaryotes, tissues are specialised and most of them have organs, mostly highly responsive. Only gametes are haploid, fertilisation

What are histogenesis and organogenesis, What are histogenesis and organoge...

What are histogenesis and organogenesis? Histogenesis is the procedure of tissue formation in the embryonic development. Organogenesis is the process of organ formation. Before

How to make ER membrane protein transfer to plasma m, how to make a membran...

how to make a membrane protein which in ER transfer to PM. whether can cut some amino of sequence which play as signal guide the protein to where could the problem

Are all pneumonias caused by bacteria, Q. Are all pneumonias caused by bact...

Q. Are all pneumonias caused by bacteria? The Pneumonia is the generic name of inflammation of the lungs. Moreover bacterial pneumonias, there are pneumonias caused by fungi, v

Display schematically and give all data, Through Nuclear transfer how Dolly...

Through Nuclear transfer how Dolly came into the picture. Show schematically and give all data.

What is defective colour vision, What is Defective Colour Vision Defect...

What is Defective Colour Vision Defective colour vision is often called colour blindness. The ability to appreciate one or more of the primary colours is lacking. This can be e

Zooflagellates – protozoan, Zooflagellates – Protozoan Zooflagellates ...

Zooflagellates – Protozoan Zooflagellates are heterotrophs that are free living, commensals or symbiotic or parasitic in other animals. A number of species eg. Trichonynzpha a

Extracted chlorophyll pigments, Extracted chlorophyll pigments If we...

Extracted chlorophyll pigments If we take chlorophyll molecule in a test tube and provide 2 CO and water and expose the mixture to sunlight, glucose is not formed. If we

Health conditions, 2. Mr Konarski, 73 years old, lives in a high-level care...

2. Mr Konarski, 73 years old, lives in a high-level care facility. He has dementia of the Alzheimer''s type, osteoarthritis in both knees and ankles, and hypertension, which is con

Precautions for detection of number of bacteria in milk, Explain the Precau...

Explain the Precautions for Detection of Number of Bacteria in Milk? 1. Make a thin film of milk on the slide. 2. Do not over stain with methylene blue.  If over staining ha

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