Fate of blastopore, Biology

Assignment Help:

Fate of Blastopore

Cleavage results in the formation of a ball of cells called morula (resembling mulberry hence the name). A space appears in the morula changing it to a hollow blastula. The central cavity is called the blastocoel and the layers of cells surrounding it the blastoderm. Invagination or infolding of the blastoderm gives rise to a double walled gastrula. The cavity of this double walled cup is called archenteron and the opening of the archenteron to the outside is called the blastopore.

2395_Fate of Blastopore.png

Figure: Early embryology of a nemertean worm a protostome

As the gastrula develops further, 'parts of the embryo give rise to different structures to ultimately form a complete young one. In platyhelminths, nematodes, annelids, arthropods and molluscs that have spiral cleavage, the embryonic blastopore forms the mouth of the animal and the anus is formed secondarily. Because the mouth forms first these animals are included in 'Protostomia' (mouth first) division of Animal Kingdom. In echinoderms, chaetognaths, hemichordates and chordates where radial cleavage takes place, the blastopore forms the anus of the animal and the mouth is formed secondarily, as an independent opening on the body wall as seen in Figure. Therefore, these animals are included in 'Deuterostomia' (mouth second), division of the Animal Kingdom.

The fate of the blastopore thus determines two fundamental lines of evolution. The protostomes in which the cleavage is generally mosaic (determinate and spiral) and the Deuterostomes in which the cleavage is usually regulative (radial and indeterminate) type.


Related Discussions:- Fate of blastopore

Regulation of respiration in a child, Describe the factors that are involve...

Describe the factors that are involved in the regulation of respiration in a child who decides to hold his/her breath for as long as possible.

Medtronic-hall valve-types of valves, Medtronic-Hall Valve :  This is...

Medtronic-Hall Valve :  This is a low profile central tilting disc valve. The disc is made of pyrolitic carbon and housing is single piece of machined titanium. Introduced in

Fission - asexual reproduction, Normal 0 false false false ...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Mitral valve replacement -mitral valve disease, Mitral Valve Replacement : ...

Mitral Valve Replacement :  Patients who require surgery and are not candidates for BMV, CMV or OMV should have mitral valve replacement (MVR). Types of Surgery for Mitra

Zoology, give the discriptive account of nerilla which belongs to class a...

give the discriptive account of nerilla which belongs to class arciannelida in phylum annelida

What is exudative diarrhoea, Q. What is Exudative diarrhoea? Exudative ...

Q. What is Exudative diarrhoea? Exudative diarrhoea: It is associated with the mucosal damage leading to out pouring of mucus, blood and plasma proteins with a net accumulation

What are the symptoms of rheumatic heart disease, Q. What are the symptoms ...

Q. What are the symptoms of Rheumatic Heart Disease? Symptoms generally appear after 1 to 6 weeks of the fever and sometimes the infection may have been too mild to have been r

Explain entecavir, Explain Entecavir  Entecavir  (Baraclude) taken ora...

Explain Entecavir  Entecavir  (Baraclude) taken orally once a day as monotherapy appears to be superior to lamivudine for patients with chronic HBV infection, but susceptibili

Characteristics of the age pyramids of developed countries, Q. What are the...

Q. What are the main characteristics of the age pyramids of developed countries? In the stabilized human population the age pyramid has a narrower base since the reproduction r

Procedure - separation of amino acid by paper chromatography, Explain Proce...

Explain Procedure for Separation of Amino Acids by Paper Chromatography? Now carry out the procedure following the steps given herewith: 1. Take a circular Whatman No 1 filt

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