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

Different types of gas exchange in animals, Q What are the different kinds ...

Q What are the different kinds of gas exchange that occur in animals? In beings from the kingdom Animalia the gas exchange may occur either by diffusion, cutaneous respiration,

What is interspecific competition in ecology explain, What is Interspecific...

What is Interspecific Competition in ecology explain? Populations in nature usually share their surrounding environment in time and space with populations of other species. If

Which are the types of neurons, Which are the types of neurons that partici...

Which are the types of neurons that participate in the spinal arch reflex? Where are their cell bodies situated? In the arch reflex first a sensory neuron located in the gangli

What do you mean by diabetes mellitus, Q. What do you mean by Diabetes Mell...

Q. What do you mean by Diabetes Mellitus? Diabetes Mellitus as you know is a metabolic disorder, which is characterized by high blood sugar. It is a chronic disease condition,

Use of toxic amino acids, Q. Explain Use of Toxic amino acids? Lathyru...

Q. Explain Use of Toxic amino acids? Lathyrus sativus (kesari dhal) seeds contain toxic amino acid beta-oxalyl aminoalanine (BOAA), is considered to be responsible

Parts of a typical flower with all its definations , parts of a typical fl...

parts of a typical flower? define its parts and internal parts completely? show complete colourful diagram?

Post-operative nursing care of a child with cleft lip, Post-operative Care ...

Post-operative Care   The goals of care during post-operative period include:  Prevent the baby from sucking and crying to avoid tension on suture line.  Give proper p

Haccp control measure, HACCP Control Measure HACCP Control Measure : ...

HACCP Control Measure HACCP Control Measure :  Any action or activity that can be used to prevent, eliminate or reduce a significant hazard.

Explain operation for patients with high pvr, Explain Operation for Patient...

Explain Operation for Patients with High Pulmonary Vascular Resistance ? When the pulmonary vascular resistance is very high (6-8 units/m2) closure of ASD is done either with

Define the stress response - nutrition during stress, Define the Stress Res...

Define the Stress Response - nutrition during stress? The terms trauma, stress, shock are very often used interchangeably and encompass a variety of conditions such as sepsis

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