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

What is polyethylene, Q. What is Polyethylene? Polyethylene (P) (Low de...

Q. What is Polyethylene? Polyethylene (P) (Low density polyethylene (LDPE), medium density, linear low-density (LLDPE), high-density polyethylene (HDPE) and ethylene vinyl acet

Meat curing and smoking, Cu r in g and Smoking Meat curing refers to...

Cu r in g and Smoking Meat curing refers to the production of the characteristic thermally stable pink meat pigment and cured meat flavour by the action of sodium nitrite an

Name the different level of proteins, Name the different level of proteins ...

Name the different level of proteins There are 4 level of proteins:- a) Primary structure b) Secondary structure c) Tertiary structure d) Quaternary structure

Why is it not correct to assert that the dna, Q. Why is it not correct to a...

Q. Why is it not correct to assert that the DNA self- replicates? The DNA is not completely self-sufficient in its duplication process because the replication does not occur wi

Haustorial behavior of embryo sac, Haustorial Behavior of Embryo Sac ...

Haustorial Behavior of Embryo Sac There are instances in which the entire embryo sac may grow beyond the ovular tissue. The central cell may also form multicellular projectio

Can you explain hormones, Q. What are hormones? Hormones are substances...

Q. What are hormones? Hormones are substances collected by the circulation and secreted by the endocrine glands that act to produce effects upon specific tissues and organs and

Explain 2nd type of hypersensitivity, It is IgG mediated cytotoxic hyperse...

It is IgG mediated cytotoxic hypersensitivity. Typical manifestations contain erythroblastosis fetalis, hemolytic anemia, blood transfusion reactions etc.

How old is the universe, How old is the universe? From the analysis of ...

How old is the universe? From the analysis of data collected by the Hubble telescope the age of the universe is estimated to be about 12 billion years.

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