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

How is the nervous system of molluscs organized, How is the nervous system ...

How is the nervous system of molluscs organized? Molluscs have well-developed sensory structures. It is established that cephalopods, such as squid and octopus, have eyes with

What is the parasite that causes toxoplasmosis, What is the parasite that c...

What is the parasite that causes toxoplasmosis? How is the disease transmitted and what are its typical manifestations? Toxoplasmosis is caused by the protozoan Toxoplasma gond

Internal mammary artery-long term patency, Internal Mammary Artery (1MA) : ...

Internal Mammary Artery (1MA) :  This is an excellent graft. When left internal mammary artery (LIMA) is anastomosed to LAD, which has more than 70 per cent block, patency at

Functions of albumin and myosin, Q. What are respectively some remarkable f...

Q. What are respectively some remarkable functions of albumin, myosin, CD 4 , keratin, immunoglobulin, reverse transcriptase, hemoglobin and insulin? Myosin is a protein that w

Currents in estuaries, Currents in Estuaries Currents in estuaries are...

Currents in Estuaries Currents in estuaries are caused primarily by tidal action and river flow. Currents are generally confined to channels but velocities up to several knots

Homework, 1) a) Initially, how do skeletal muscles (the type of muscle atta...

1) a) Initially, how do skeletal muscles (the type of muscle attached to bones) make ATP? b) write the reaction for this procss (Crp +ADP => Cr + ATP) as a ''coupled'' reaction, id

Define nutritional requirements for young and older children, Define Nutrit...

Define Nutritional requirements for Young and Older Children? Young children need 3 en%, which would be easily met from 8-10 g of oil. However, more visible oil is needed to im

Name the compound that is phosphorylated for atp formation, What is the com...

What is the compound that is phosphorylated for ATP formation? What is the resulting compound when ATP liberates energy? ATP, or adenosine triphosphate, is produced after the

How all the exercises are active exercises, How All these exercises are act...

How All these exercises are active exercises All these exercises are active exercises that is active exercises are those type of physical activities carried out by the individ

Endothelium derived relaxing factors, Vasoactive substances such as Endothe...

Vasoactive substances such as Endothelium Derived Relaxing Factors (EDRF). Prostacyclin and Endothelin can be formed in the vascular endothelium. Endothelial dysfunction can lead t

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