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 a recessive gene, What is a recessive gene? With the birth of a...

What is a recessive gene? With the birth of a child, it gets its genes from both parents. Some genes 'override' other genes. Using hair color as instance: If single parent i

Which elements contains carbohydrates, (a) Which elements contains Carbohyd...

(a) Which elements contains Carbohydrates (b) Which elements contains Proteins   a) Carbohydrates contain the elements carbon , hydrogen and oxygen. b) Protei

Define the buffer capacity - nutritional biochemistry, Define the Buffer ca...

Define the Buffer capacity - Nutritional Biochemistry? Buffer capacity can be defined as, 'the capacity of a solution to resist changes in pH on the addition of strong acid or

Calculate the volume of a 25% urethane, Assume that the blood volume of a r...

Assume that the blood volume of a rabbit is 0.5 liters. If the effective dose of the anesthetic urethane is 10 µgrams/ml of blood, calculate the volume of a 25% urethane solution t

Non-consumptive value, This is concerned more with nature's services which ...

This is concerned more with nature's services which also make vital contributions to the welfare of society and to ecological processes without which our planet would be uninhabita

Importance of forests - fuel wood, Importance of Forests - Fuel Wood T...

Importance of Forests - Fuel Wood The forests are renewable resources which provide us a wide variety of commodities. For man, forests have been a source of recreation and the

Social determinants of health - food, Social Determinants of Health - Food ...

Social Determinants of Health - Food The twin paradox of food i.e., research showing excessive intake can lead to a variety of diseases whilst at the same time food poverty be

Define bacterial photosynthesis, Cyanobacteria carry out photosynthesis usi...

Cyanobacteria carry out photosynthesis using two photosystems as in green plants. Furthermore, other photosynthetic bacteria, like as the purple photosynthetic bacterium Rhodospiri

Zygote and fecundation formation occur in these plants, Q. How do zygote an...

Q. How do zygote and fecundation formation occur in these plants? Do these processes depend on water? The microsporangia in the male strobile rupture at the right time of the y

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