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

Define effect of nutrition on the immune system, Define Effect of Nutrition...

Define Effect of Nutrition on the Immune System? Nutrition has a strong influence on the immune system of the elderly. Ageing induces dysregulation of the immune system, mainly

Determine about the colloblast cell, Determine about the Colloblast cell? ...

Determine about the Colloblast cell? The unique sticky discharge cells found in the tentacles of ctenophorans. They are used to capture prey, and although cnidoblasts resemble

Brucellosis, Br u c e ll osi s It is also called as Bang's diseas...

Br u c e ll osi s It is also called as Bang's disease or contagious abortion as it causes abortion in late pregnancy and infertility. E t iology: It is cause

What are the major bone surfaces, Bone Surfaces:  There are four major bon...

Bone Surfaces:  There are four major bone surfaces: 1) Periosteal (outer surface of all bones) 2) Endosteal (inner surface of cortical bone) 3) Haversian (inner surface o

Explain selective breeding methods, Explains how selective breeding methods...

Explains how selective breeding methods could be used to produce a population of cats with the short legs. Selective breeding E1: bases explanation on the assumption t

Explain the types of modified gellan gum, Explain the types of modified gel...

Explain the types of modified gellan gum There are 3 types of modified gellan gum.  (a) High acetyl gellan (partially deacetylated), which provides a thermo reversible gel,

What are the two techniques of submerged implants, Submerged implants Decis...

Submerged implants Decision has to be made between two techniques. These techniques are: Technique 1: Stage two using a mucoperiosteal flap Technique 2: Stage two done wi

Define historical development of food processing, Define Historical Develop...

Define Historical Development of Food Processing? Food processing began thousands of years ago to help people keep food through the lean seasons. Several methods of preserving

Which is utilized by other reactions, The breakdown of ATP releases energy,...

The breakdown of ATP releases energy, which is utilized by other reactions that require energy. Identify other examples where inventions have utilized a similar principle, where en

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