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 is cryopreservation, Name the location and function of Meibomian gland...

Name the location and function of Meibomian glands in the human eye. a) What is cryopreservation? Give its single use. b) Commercial importance of cryopreservation is relate

ASSINMENT, HISTORY ON CLASSIFICATION IN BIOLOGY

HISTORY ON CLASSIFICATION IN BIOLOGY

International codes used for system of binomial nomenclature, Q. Internatio...

Q. International Codes used for system of binomial nomenclature? In 1753 Linnaeus suggested a system of binomial nomenclature where each individual is denoted by two epithets,

Golgi apparatus, GOLGI APPARATUS Camillo Golgi in 1898 discovered a retic...

GOLGI APPARATUS Camillo Golgi in 1898 discovered a reticular structure in the cytoplasm of nerve cells with the help of metal impregnation technique using silver nitrate for whic

Removal of impurities in water, Many common methods are employed for the re...

Many common methods are employed for the removal of impurities from water. Some of them are: Sedimentation Filtration Reverse osmosis Electro dialysis Aeration

What do you mean by current impediments, Q. What do you mean by Current Imp...

Q. What do you mean by Current Impediments? Given the impressive list of past achievements, we expect that quantitative process to biological problems will continue to repay us

Define incision - endodontic surgery, Define Incision - Endodontic Surgery ...

Define Incision - Endodontic Surgery Incisions are accomplished by using one of four scalpel blades: No. 11, No.  12, No. 15, and No. 15-C Horizontal incision should be m

Why bacteria called extremophiles, Bacteria called extremophiles are able t...

Bacteria called extremophiles are able to grow in hot springs such as Old Faithful at Yellowstone National Park in Wyoming. Do you think that the DNA of extremophiles would have a

Define nutrient requirements during the periods of pregnancy, Define nutrie...

Define nutrient requirements during the periods of pregnancy? In the previous unit, we learnt about the basic principles of meal planning and the various considerations and gui

Normal pigmentation, The female I-1 and her mate, male I-2, had four childr...

The female I-1 and her mate, male I-2, had four children, one of whom has albinism. What is the probability that they could have had a total of four children with any other outcome

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