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

What do you understand by parapodia, What do you understand by Parapodia? ...

What do you understand by Parapodia? Paired lateral, unjointed appendages of polychaete worms. Parapodia have a variety of shapes, and their appearance is related to their nume

Biosphere, Biosphere Biosphere is that part of the earth where life can...

Biosphere Biosphere is that part of the earth where life can exist. It is a narfqy layer around the surface of the earth. If you visualise the earth to be the size of an apple

Explain the importance of nicotinic acid, Explain the Importance of nicotin...

Explain the Importance of nicotinic acid Nicotinic acid is successfully used in the therapy of a number of vascular disorders such as vascular spasms, angina pectoris, arthriti

Denitrifying bacteria play in the nitrogen cycle, What part do (a) nitrifyi...

What part do (a) nitrifying, (b) nitrogen-fixing and (c) denitrifying bacteria play in the nitrogen cycle? a) Nitrifying bacteria in the soil change ammonia and other nitrogeno

Determine the stage 1 implant surgery, Determine the stage 1 implant surger...

Determine the stage 1 implant surgery Following stage 1 surgery, prior to commencing on the prosthetic procedures in the conventional loading protocol it is critical that the s

Secondary induction, Secondary Induction The two primary inductive ev...

Secondary Induction The two primary inductive events that we have described so far are significant in the patterning of early embryo. But there are another such signaling eve

Byproducts of low digestibility and low nitrogen, Byproducts of low digesti...

Byproducts of low digestibility and low nitrogen Straws, husks, pods and haulms are the byproducts of this category. Very often the nitrogen content in these byproducts is so l

What is yellow fever, Q. What is yellow fever? The Yellow fever is a vi...

Q. What is yellow fever? The Yellow fever is a viral infection that occurs mainly in Central Africa and in the Amazon region of South America. It is prevented by vaccination an

Blood from the fetus circulates through the placenta, Blood from the fetus ...

Blood from the fetus circulates through the placenta. a) What substances pass (i) from the maternal to the fetal blood, (ii) from the fetal to the maternal blood?

Analytic characters - nature and structure of community, Analytic Character...

Analytic Characters - Nature and Structure of Community As you know a community has its own characteristics. Which are not shown by its individual component species. These cha

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