Answer:
The correct answer will be option-
1. UV light strikes the skin and converts a steroid molecule into an inactive form of vitamin D.
2. Inactive vitamin D is transported to the liver where it is modified.
3. Vitamin D is activated under the influence of PTH.
4. Inactive, chemically altered vitamin D is transported to the kidneys.
Explanation:
Vitamin D is a fat-soluble metabolite which helps maintain the health of the bone by maintaining the calcium homeostasis.
The vitamin D is synthesized mainly in the liver and kidney from the biologically inactive precursor of vitamin D called ergocalciferol and Cholecalciferol.
The inactive vitamin is synthesized in the skin when the skin is exposed to UV rays. The UV rays convert the 7-dehydrocholesterol, a steroid molecule to Vitamin D3, This inactive vitamin is then transported to the liver where it is converted to 25-hydroxyvitamin D.
This vitamin D form is further metabolized in the kidney controlled and regulated by the Parathyroid glands.
Answer;
Scleroderma
Scleroderma is a connective tissue disorder that is characterized by insoluble collagen being formed and accumulating excessively in the tissues.
Explanation;
This disorder features thickened skin that can involve scarring, blood vessel problems, varying degrees of inflammation and pain, and is normally associated with an overactive immune system. It is regarded as an autoimmune condition, as the body produces too much collagen, causing the skin and connective tissue to thicken.
Answer:
An index fossil is also known as guide fossils or indicator fossil. They are fossils used to determine and identify geologic periods.
The main characteristics of an index fossil include :
1.It must be distinctive.
2.It must be widespread.
3. It must be abundant
4. It must be limited in geologic time.
Due to trends and studies of most fossil-bearing rocks being formed in the ocean, the major index fossils are mostly marine animal or plant organisms.
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