Threshold value of different larval tissues, Biology

Assignment Help:

Threshold Value of Different Larval Tissues

Threshold value of dissimilar larval tissues for the thyroid hormone concentration

One of the main problems of metamorphosis is the co-ordination of developmental events. The tail should not degenerate till some another means of locomotion, namely the limbs develop, and the gills should not regress till the animal can employ its newly developed lung muscles. Kollros (1961) illustrated the possibility of this coordination that displays that different larval tissues have diverse threshold value for thyroxine. In other words the different larval tissues are sensitive to dissimilar concentrations of thyroid hormone.

This model is termed as the threshold concept. It has been observed that structures in the tadpole that change early during metamorphosis are more sensitive to and have low threshold value to thyroxine, than those which go through transformation at a later stage. As metamorphosis commences the thyroid hormone level slowly builds up and different events occur at different concentrations of the hormone. Experimental studies have revealed that tadpole pans that have a low threshold respond earlier during metamorphoses than those parts comprising a high threshold response. In other words, the threshold value reflects the order where metamorphic changes occur in normal development. In urodeles the bulging of eyes reacts to the weakest dose of thyroid hormone (minimum threshold) and thus is the first event in metamorphosis. This is followed by reduction of fin fold and the shortening and disappearance of external gills. After which takes place the closure of gill clefts and transformation of skin.

 


Related Discussions:- Threshold value of different larval tissues

Define the rehabilitation phase of spinal trauma disease, Define the Rehabi...

Define the Rehabilitation Phase of spinal trauma disease? Once the patient s condition stabilizes, individualized diets need to be recommended, based on the energy and nutrient

Class polychaeta - classification of coelom, Class Polychaeta - Classificat...

Class Polychaeta - Classification of Coelom There are mainly marine forms with distinct head, having eyes and tentacles, segments have lateral projections of the body wall ter

Pressure flow mechanism for translocation, experiments that support pressur...

experiments that support pressure flow as a mechanism for translocation

What is optic chiasma, What is Optic Chiasma  This structure makes upto...

What is Optic Chiasma  This structure makes upto portion of the anterior inferior floor of the third ventricle. It is shaped like a flat oblong bridge and connects the optic ne

What are the symptom of short bowel syndrome, Q. What are the Symptom of sh...

Q. What are the Symptom of short bowel syndrome? Diarrhoea is the main symptom of short bowel syndrome. Other symptoms include: • Anorexia • Steatorrhoea • Heart bum a

Describe the process of crassulacean acid metabolism, Describe the process ...

Describe the process of Crassulacean acid metabolism. a) How is it advantageous to plants? b) Describe the major steps in Krebs cycle. Why is this cycle also called citric a

Define about oxygen molecule, How many pairs of electrons do the two oxygen...

How many pairs of electrons do the two oxygen atoms in an oxygen molecule share with each  other? Explain your answer. The oxygen atoms share two pairs of electrons, sinc

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