UPSC 1996 Science and Technology Questions with Answers

Explanation

Option 1, 2 and 4 are correct: AIDS (Acquired Immunodeficiency Syndrome), caused by the HIV virus, is transmitted through:

Sexual intercourse: HIV is primarily transmitted through unprotected sexual contact, including vaginal and anal intercourse with an infected partner. The virus is present in bodily fluids such as semen and vaginal secretions. Blood transfusion: Receiving blood transfusions contaminated with HIV can transmit the virus. HIV can be transmitted from an infected mother to her child during pregnancy, childbirth, or breastfeeding. This mode of transmission is known as vertical or mother-to-child transmission. It is transferred from an infected mother to her foetus across the placenta. These are the primary modes of transmission as confirmed by WHO. Option 3 is incorrect: HIV cannot be transmitted through mosquitoes or other blood-sucking insects because the HIV virus does not survive or replicate in these organisms.

Explanation

Malnutrition refers to a state of improper nutrition, which can arise from overnutrition (excess intake of food or nutrients), undernutrition (deficiency of essential nutrients), and imbalanced nutrition (inadequate or excessive intake of specific nutrients relative to others). Overnutrition: Consuming excessive calories or nutrients can lead to obesity and associated health issues like diabetes, cardiovascular diseases, and metabolic disorders. Undernutrition: A lack of essential nutrients causes deficiencies like protein-energy malnutrition (e.g., kwashiorkor, marasmus), anemia, and weakened immunity. Imbalanced nutrition: A diet lacking in proper proportions of macronutrients (carbohydrates, proteins, fats) and micronutrients (vitamins, minerals) can cause health problems, even if calorie intake is sufficient. All these conditions impair the body’s ability to function optimally and lead to health complications.

Explanation

Fluorosis results from prolonged excessive fluoride intake, leading to alterations in tooth enamel (dental fluorosis) or bone structure (skeletal fluorosis). It is commonly linked to water sources with high natural fluoride levels such as deep wells that access fluoride-rich geological formations. Since shallow hand pumps draw water from near the surface so they are less likely to contain such high fluoride concentrations. Options (a), (b), and (c) are incorrect:

Cholera, typhoid, and jaundice are caused by microbial or viral contamination of shallow water sources, making them common risks. These diseases are not linked to deep underground water. Cholera: A severe diarrheal disease caused by Vibrio cholerae, primarily spread through contaminated water and food. Typhoid: A bacterial infection caused by Salmonella typhi, characterized by high fever, weakness, and gastrointestinal symptoms. Jaundice: A condition marked by yellowing of the skin and eyes due to excess bilirubin, often caused by liver disease, hepatitis, or bile duct obstruction.

Explanation

Besides proteins and carbohydrates, milk is a rich source of calcium and potassium, which are essential for strong bones, teeth, and maintaining fluid balance. Calcium is essential for bone health, muscle function and nerve signaling. Potassium is an important electrolyte that helps regulate fluid balance, muscle contractions and nerve signals.

Explanation

Subcutaneous fat is a layer of fat located just beneath the skin. It primarily acts as an insulator which reduces heat loss from the body by trapping heat and maintaining body temperature. This insulation is particularly beneficial in cold environments, helping to conserve energy and prevent hypothermia.

Explanation

Option (c) is correct: The major chemical compound that constitutes kidney stones is Calcium Oxalate. These stones are common and can cause severe pain during urination. Calcium oxalate is formed when calcium in the urine binds with oxalate, a compound found in certain foods (e.g., spinach, nuts) or produced as a by-product of metabolism. High concentrations of calcium and oxalate in urine, combined with low fluid intake, promote the crystallization of calcium oxalate. Options (a), (b), and (d) are incorrect: Urea is not a major component of kidney stones because it is a waste product of protein metabolism that is typically excreted in the urine. Other types of kidney stones can contain calcium carbonate, calcium phosphate, uric acid, or struvite, but calcium oxalate stones are the most common. Factors such as dehydration, high oxalate intake, and certain medical conditions can increase the risk of kidney stone formation.