Types of blastula, Biology

TYPES OF BLASTULA -

Blastulas are of following type -

1567_blastulation.png                  876_blastulation1.png

1.       STEREOBLASTULA -

The blastocoel is very small. It's blastomere are less in number but large in size.

It is formed as a result of spiral cleavage. eg. Neries and some molluscs.

2.       COELOBLASTULA -

The blastula of echinoderm and amphioxis is called coeloblastula.

It is formed through complete holoblastic cleavage. The blastoderm is formed of a single layer of cells.

Its blastocoel is filled wiht mucopolysaccaharide. In microlecithal egg blastocoel is centric.

In megalecithal egg blastocoel is excentric, eg. Some animal of echinodermes and amphioxis.

3.       PERIBLASTULA OR SUPERFICIAL BLASTULA -

It is formed as a result of superficial cleavage. The blastocoel is absent.

There is a single layer of blastomeres around the uncleaved yolky part, eg. Insect.

4.       DISCOBLASTULA -

It is formed as a result of discoidal cleavage. The blastocoel is small & it is called as subgerminal space. It is situated below the blastoderm, eg. Boney fishes, reptile, birds & prototherian mammals.

1732_blastula.png

5.      AMPHIBLASTULA -

It is formed of two types of structurally different blastomeres.

Example, in sycon the anterior half fo blastula is formed of flagellated cells while the posterior half is formed of large rounded granular cells on in amphibians where the two types of cells are micromeres and macromeres.

eg. Amphibians.

6.      BLASTOCYST -

It is formed in mammals as a result of holoblastic cleavage.

Outer cells are called as trophoblasts or cells of Rauber. They form a trophoderm. This layer get attached to the uterine wall.

Inner cells form the embryo & are called as inner cell mass.

eg. Human beings.

1893_types of blastula.png

Posted Date: 10/3/2012 9:23:47 AM | Location : United States







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

Write discussion on Types of blastula
Your posts are moderated
Related Questions
A kinase is in general an enzyme which catalyzes the transfer of the phosphate group from ATP to something else. In the molecular biology, it has acquired the more specific verbal

What are the extraembryonic membranes present in vertebrates? The extraembryonic membranes that might be present in vertebrates are the yolk sac, the amnion, the chorion, the

Microtubule assembly: A) generally originates in the centrosome. B) Occurs only during mitosis. C) Occurs randomly throughout the cell. D) Is regulated by myosin. E) Is inhibited d

The first evidence of implants dates back to 600 A.D. in the Mayan population. There are reports that the ancient Egyptians attempted intra-osseous implantation of animal teeth or

Describe the properties of gum ghatti Important property of gums referred to as 'viscosity' and the effets of pH. Gum ghatti does not form true aqueous solutions but form visco

Define Techniques for Measuring Body Composition - Underwater weighing? Underwater weighing (densitometry): It applies the Archimedean principle of water displacement by the fu

Can all the four chambers of the human heart experience systole simultaneously? Describe justifying your answer. What do you call the circulatory fluid in the body of cockroach

Define Gonads and Reproductive System? With aging, there is decrease in pituitary hormone secretion causing decrease in gonadal hormone production, which causes number of chang

Determinants of Health Status The linkage between economic development and health was discussed in the previous unit. The present unit deals with an identification of the factor

Liverworts and mosses are characterized by their lack of vascular conducting tissue. These two groups of liverwort, plants and mosses, are known by which of the below terms: a)