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

Explain about individual consciousness, Q. Explain about Individual conscio...

Q. Explain about Individual consciousness? The physical brain is not a source of experience as some current neuroscientists now mistakenly believe. While areas of the brain are

Heredity, in humans, maleness of is determined by a pair of sex chromosomes...

in humans, maleness of is determined by a pair of sex chromosomes called X and Y. (a)what is the genotype for males? (b)what is the genotype for females?

Difference between micronutrients and macro, Q. What is the difference betw...

Q. What is the difference between micronutrients and macro? The classification criterion of nutrients into micronutrients and macro has no relation to the size of the molecul

Explain the indole production test, Explain the Indole Production Test? ...

Explain the Indole Production Test? Many microorganisms produce an enzyme tryptophanase which oxidizes amino acid tryptophan to produce pyruvic acid, indole and ammonia. We can

Types of leukemia, Types of Leukemia Leukaemia may be chronic  or acut...

Types of Leukemia Leukaemia may be chronic  or acute and is classified  into  the  following  categories:  i)  Acute Lymphocytic Leukaemia (ALL) This is  the most comm

What is the disease caused by vitamin d deficiency, What is the disease cau...

What is the disease caused by vitamin D deficiency? Which tissue does it affect? The lack of vitamin D causes the disease called as rickets (rachitis), characterized by decalci

Excretion, what is the excretory organ of lizard

what is the excretory organ of lizard

Explain hormones, What are hormones? Hormones are substances secreted b...

What are hormones? Hormones are substances secreted by the endocrine glands and collected by the circulation that act to make effects upon exact organs and tissues. Hormones

How much protein is in the red blood cell, I need a list of equipment neces...

I need a list of equipment necessary to complete it as well as a method to isolate the cell parts, how much protein is in the red blood cell as well as the amount of DNA in the cel

Procedures for diagnosis - nucleic acid hybridization, Nucleic acid hybridi...

Nucleic acid hybridization: This is a process by which a suitably labeled DNA or RNA from a known infectious agent is used to probe its complementary sequence unique to 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