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

Explain lipoprotein excess, Explain Lipoprotein (Lp(a) Excess ? While c...

Explain Lipoprotein (Lp(a) Excess ? While cholesterol and triglycerides are important lipid risk factors, another lipoprotein factor called Lipoprotein (a) is thought to play a

What is the genetic code, What is the genetic code? Genetic code is the...

What is the genetic code? Genetic code is the key for the conversion of DNA nucleotide sequences (and therefore RNA nucleotide sequences) into amino acids sequences that will c

How the blood sugar level is maintained at a stable level, Discuss how the ...

Discuss how the blood sugar level is maintained at a stable level in the well fed and fasting state In  the fed state, clearance of blood  glucose is mainly by  liver via gluc

Homework, The Waldorf family was caught in a fire but escaped. Unfortunatel...

The Waldorf family was caught in a fire but escaped. Unfortunately, the father and daughter suffered burns. The father had second-degree burns on his entire chest, abdomen, and bot

How campylobacteriosis is caused, How Campylobacteriosis is caused It i...

How Campylobacteriosis is caused It is caused by  Campylobacter jejuni, a Gram-negative rod. It is a microaerophillic organism, which means it has a requirement for reduced lev

Obtain half their genes from one parent, If children obtain half their gene...

If children obtain half their genes from one parent and half from the other parent, why aren't siblings identical?

Altered glucose metabolism - metabolic response to injury, Explain the Alte...

Explain the Altered Glucose Metabolism - Metabolic Response to Injury? Following injury, hypoglycemia commonly occurs and is related to the severity of the stress. In the ebb p

What structure replaces the graafian follicle, After ovulation:- (a) ...

After ovulation:- (a) what structure replaces the Graafian follicle (b) what hormone does it produce?   (a) After ovulation, the follicle is replaced by the cor

Evaluation of osseointegration, Q. Evaluation of osseointegration? All ...

Q. Evaluation of osseointegration? All the parameters of proper implant selection, atraumatic sequential osteotomy preparation and the attainment of primary stability are focus

Chemical energy of matter, Chemical energy of matter : As is obvious from ...

Chemical energy of matter : As is obvious from  the above  account  living cells  obtain  energy  by breaking   C-C and C-H bonds  of organic  matter under the  process of catabol

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