Biology: Zoology: UPSC Previous Year Questions (Science and Technology)

Explanation

The octopus is a mollusc in the class Cephalopoda (including squids and cuttlefish), part of the phylum Mollusca. Cephalopods are soft-bodied, bilaterally symmetrical, lack external skeletons, and have prominent heads with arms or tentacles. Octopuses lack an external shell, allowing for flexibility and the ability to squeeze through tight spaces. Their eight arms, equipped with suction cups, help with locomotion, prey capture, and interaction. Octopuses are highly intelligent, demonstrating problem-solving and tool use. Mollusca is a phylum of invertebrates, including snails, clams, and cephalopods.

Explanation

The word AIDS stands for Acquired Immuno Deficiency Syndrome. This means deficiency of the immune system, acquired during the lifetime of an individual. ‘Syndrome’ means a group of symptoms. AIDS is caused by the Human Immunodeficiency Virus (HIV), a member of a group of viruses called retrovirus. It leads to various symptoms such as Swollen lymph nodes occur due to immune system deterioration, commonly affecting the neck, armpits, and groin. Night sweats and recurring fevers are signs of opportunistic infections as the body struggles to regulate temperature. Memory loss and cognitive impairment arise when the virus affects the nervous system, leading to neurological complications. Significant weight loss results from chronic infections, metabolic changes, and increased energy demands.

Explanation

Statement 1 is incorrect: The renal artery is responsible for delivering oxygenated blood from the heart to the kidneys for filtration. After the kidneys filter the blood by removing waste products and excess substances, the cleansed blood is returned to the systemic circulation via the renal vein, not the renal artery.

Statement 2 is correct: From Bowman’s capsule, the glomerular filtrate(filtered liquid) passes into the proximal convoluted tubule (PCT), where essential substances, including glucose, are actively reabsorbed. This reabsorbed glucose along with other nutrients is then transported into the peritubular capillaries and eventually returned to the bloodstream via the renal vein. This ensures that the body retains necessary nutrients while excreting waste.

Explanation

Milk does contain several B-vitamins such as Vitamin B2 (riboflavin) and Vitamin B12 (cobalamin) along with Vitamin D, calcium, and proteins. For instance, a 200ml glass of semi-skimmed milk provides approximately 0.47 mg of riboflavin, which is about 33% of the recommended daily intake. Options (b), (c) and (d) are correct:

Vitamin A is found in foods like carrots, liver, and dairy products and is crucial for maintaining healthy skin. A deficiency in vitamin A can cause xerosis (dry, scaly skin) due to its role in maintaining healthy skin and mucous membranes. Scurvy is caused by a deficiency in vitamin C. One of its symptoms is joint pain, along with others like fatigue, swollen gums, and bruising. Vitamin C is found in citrus fruits, amla, and guava. A severe deficiency in Vitamin B1(thiamine) can result in beriberi, which affects the cardiovascular system, potentially leading to heart failure. Symptoms include shortness of breath, swelling of the lower legs, and increased heart rate. It is present in whole grains, nuts, and legumes.

Explanation

Statement 1 is correct: When hydrochloric acid (HCl) from the stomach enters the duodenum, it lowers the pH of intestinal contents. This triggers S-cells in the duodenal lining to release secretin. Secretin signals the pancreas to release bicarbonate-rich fluid. This fluid neutralizes the acid, creating an optimal environment for digestive enzymes to function.

Statement 2 is correct: Enterogastrone refers to a group of hormones secreted by the duodenal mucosa when dietary fats are present. These hormones, including secretin and cholecystokinin (CCK) slows down gastric motility and inhibit stomach secretions. This regulation ensures that chyme moves gradually from the stomach to the small intestine, promoting better fat digestion and absorption.