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

Importance of reproduction, Importance of reproduction Reproduction ...

Importance of reproduction Reproduction is an important life process in animals and plants. Reproduction is the ability of an organism to produce new generation of indivi

What is the universal chemical equation of photosynthesis, Q. What is the u...

Q. What is the universal chemical equation of photosynthesis? Why does not that equation clearly show the real origin of the molecular oxygen liberated? The general equation of

Main constituents of the earth''s atmosphere in our time, What are the main...

What are the main constituents of the earth's atmosphere in our time? The present atmosphere of the earth is constituted essentially of molecular nitrogen (N2) and molecular ox

What is the respective importance of water, What is the respective importan...

What is the respective importance of water, carbon and nitrogen for living beings? Water is the major solvent of living beings and it is essential practically for all biochemic

Define surgical procedures for cancer patient, Define Surgical Procedures f...

Define Surgical Procedures for Cancer Patient Major resection of the small bowel is not common. Resection of the ileum leads to certain physiological and nutritional problems.

Radiometer-radiation instrument, Radiometer Radiometer measures the flu...

Radiometer Radiometer measures the flux of energy of all wavelengths received on a single surface of the receiver. There are also instruments that can measure the difference be

Determine the types of emulsions, Determine the types of Emulsions? A f...

Determine the types of Emulsions? A food emulsion is basically a two phase system consisting of a liquid, such as oil, wax or essential oil and water. An emulsion has 3 parts -

Explain feeding schedule in infancy, Explain Feeding Schedule in Infancy? ...

Explain Feeding Schedule in Infancy? 1) Milk feed 5-6 times/day. Continue breast-feeding. Exclusive breast-feeding up to 6 months even during illness. Follow demand feeding.

Structure of the pancreas, Describe the structure of the pancreas. How is t...

Describe the structure of the pancreas. How is the pancreas modified to carry out its various functions? How does the human pancreas compare to that of the fetal pig?

Define the term diffusion, Define the terms diffusion, osmosis and filtrati...

Define the terms diffusion, osmosis and filtration. Explain why each process is important for the human body.

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