Types of cleavage, Biology

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.

Posted Date: 1/25/2013 1:02:18 AM | Location : United States

Related Discussions:- Types of cleavage, Assignment Help, Ask Question on Types of cleavage, Get Answer, Expert's Help, Types of cleavage Discussions

Write discussion on Types of cleavage
Your posts are moderated
Related Questions
Q. What are yeast? Yeasts are unicellular fungi, which are widely distributed in nature. They are somewhat larger than bacteria. The cell length is about 10μm and the diameter

Explain the Escherichia - Characteristics of Bacteria? It belongs to order Enterobacteriales. It is the best-studied organism present in the colon of humans and other warm-bloo

SKULL- Present in head region. It is supported on the top of vertebral column. It is made up of the hardest and denest bones in the human body. It consists of cranium

Q. What are the anatomical relationships between the organs of the female reproductive system from the external vulva to the ovaries? The external female genitalia are called t

Non-recurrent Type As mentioned earlier it refers to embryo development in reduced embryo sacs. The mechanisms identified for such cases are: Reduced Pseudogamy : The

Placing the Implants in Immature Grafted Sites One of the most common causes of prosthetically related implant failure is believed to be the too rapid loading of the implant su

Q. Define the Remodeling rate? Human cortical bone: 2-10%  per year depending on site and age of patient. Trabecular bone: Higher turnover rate 20-30% per year. In a stu

Q. Which organs of the body is part of the human digestive system? The digestive system also known as "systema digestorium" or gastrointestinal system is composed of the digest

Explain about the Diabetes mellitus? You are aware that diabetes may be diagnosed as an exaggerated response in blood glucose concentration following ingestion of a fixed amou

Q. What is structural formula of glycerol? To which organic function do these molecules belong? Glycerol is a linear chain of three carbons, the central carbon is bound to one