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

Explain the alternaria - fungi, Explain the Alternaria - Fungi? Classif...

Explain the Alternaria - Fungi? Classification Kingdom - Mycetae Division - Amastigomycota Form Class - Deuteromycetes Form Subclass - Hyphomycetidae Form Order

Digestive system - pancreas, P ANCREAS It is an elongated, leaf lik...

P ANCREAS It is an elongated, leaf like, yellowish or orangish in colour. Lying partly behind stomach. 16 cm long, 2.5 cm. wide & weight about 60 gms. It consists of hea

Pseudocoelom - metazoa, Pseudocoelom - Metazoa The platyhelminths whic...

Pseudocoelom - Metazoa The platyhelminths which do not have a body cavity surrounding the gut, have a solid type of body constitution. The mesoderm completely fills the space

Define microorganism in fermentation foods process, Normal 0 fa...

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

Rock be well-known from living things, Critical thinking the organization o...

Critical thinking the organization of a rock is much simpler than that of living things. By what other criteria can a rock be well-known from living things? Rocks are not comp

Zoonotic diseases-classification in terms of reservoir host, Classification...

Classification in terms of reservoir host 1.  Anthropozoonoses: Infections transmitted from lower vertebrate to man, e.g., rabies, plague, leptospirosis, etc. 2.   Zooanthro

List out the principles of food preservation, List out the Principles of Fo...

List out the Principles of Food Preservation? All food preservation methods are based upon the general principle of preventing or retarding the causes of spoilage caused by mic

Define sterol regulatory element binding proteins (srebps), Define Sterol R...

Define Sterol Regulatory Element Binding Proteins (SREBPS)? These belong to a general family of transcription factors. They are synthesized as membrane embedded proteins in res

What is facultative anaerobic beings, What is the difference between facult...

What is the difference between facultative anaerobic beings and obligate anaerobic beings? Facultative anaerobic beings, such as the fungi Saccharomyces cerevisiae, a brewing y

Can we make artificial cells, Q. Can we make artificial cells? Research...

Q. Can we make artificial cells? Research in progress at the "National Aeronautical and Space Administration (NASA)" is focused on artificial cells as a means to deliver medici

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