Types of cleavage, Biology

Assignment Help:

Types of Cleavage

a) Radial Type: If each of the blastomeres of upper tier lies exactly over the corresponding blastomeres of the lower tier the pattern of cleavage is radially symmetrical i.e. blastomeres are arranged along the radii of the sphere, e.g. echinoderms, Amphioxus, amphibians.

b) Spiral Type: The upper tier of blastomeres of 8-cell stage embryo may be shifted with respect to the lower tier so that radially symmetrical arrangement of blastomeres is distorted in various degrees. In such a case the blastomeres of the upper tier do not lie exactly over the corresponding blastomeres of the lower tier.

Instead, all the blastomeres of upper tier are shifted in the same direction with respect to all the blastomeres of the lower tier. This position results from the oblique position of mitotic spindle so that, from the start, two daughter blastomeres do not lie one above the other, e.g., annelids, molluscs, some helminths of order polycladida.


Related Discussions:- Types of cleavage

Causes of diabetic ketoacidosis, Q. Causes of Diabetic Ketoacidosis? Th...

Q. Causes of Diabetic Ketoacidosis? The causes of Diabetic Ketoacidosis (DKA) are the following: - Missing of insulin injection - Infection - Trauma (injury) - Myoc

Body cavity and coelom - metazoa, Body Cavity and Coelom - Metazoa Vac...

Body Cavity and Coelom - Metazoa Vacuoles, spaces, lacunae and cavities have been of importance in all organisms, may it a be plant or animal. All animals have cavities. The c

Where is the patient most likely to experience, The most recent blood work ...

The most recent blood work of a patient with a diagnosis of acute myelogenous leukemia (AML) reveals thrombocytopenia. Where is the patient most likely to experience abnormal bleed

Metaphase chromosomes, Metaphase chromosomes: Each metaphase chromoso...

Metaphase chromosomes: Each metaphase chromosomes is a duplicated structure which consists of two sister chromatids, attached at a point called centromere or primary constric

Phylum protozoa, what are the classfication and members af phylum protozoa

what are the classfication and members af phylum protozoa

Determine the fransworth 100 hue panel test, Determine the Fransworth 100 H...

Determine the Fransworth 100 Hue Panel Test This is a simple and useful test using colour chips arranged in a particular sequence. Colour deficient patients make errors in arra

What si adenosine or dipyridamole thallium scan, Q. What si Adenosine or Di...

Q. What si Adenosine or Dipyridamole Thallium Scan? These studies are newer modalities that allow studying perfusion abnormalities to the myocardium when the patient cannot per

Embryology, what is meaning of haustoria

what is meaning of haustoria

Which hormones produced by ovaries and testicles, Q. What are the hormones ...

Q. What are the hormones produced by the ovaries and the testicles? The testicles make androgenic hormones, the major of them being testosterone. The ovaries produce progestero

Can you explain vestibular system, Q. What is the vestibular system? How do...

Q. What is the vestibular system? How does it operate? The vestibular system is the part of the ear that participates in the regulation and control of the equilibrium of the bo

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