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

Explanation

Statement 1 is incorrect: Pangolins (scaly anteaters) are fascinating toothless mammals covered in protective keratin scales. They use their long, sticky tongues to capture ants and termites, making them nature’s pest controllers. India is home to two species of pangolins:

Indian Pangolin (Manis crassicaudata) is found across most parts of India, except for the northeastern states. Chinese Pangolin (Manis pentadactyla) inhabits the forests of northeast India, including Assam, Arunachal Pradesh, and Meghalaya. Pangolins are the most trafficked mammals in the world due to demand for their scales and meat.

Statement 2 is correct: Hoolock Gibbon is India’s only ape species and is a true acrobat of the rainforest. Unlike monkeys, gibbons lack tails and move gracefully through the trees using brachiation (swinging from branch to branch). These lesser apes are found in Northeast India, especially in Assam (Hoollongapar Gibbon Sanctuary) Arunachal Pradesh, Meghalaya, Mizoram, Manipur, Nagaland and Tripura. Hoolock gibbons are known for their melodious calls, which echo through the dense forests. Sadly, habitat destruction and deforestation have put them at risk.

Explanation

The term "long bone" refers to bones that are longer than they are wide such as the femur and humerus. The bone marrow within these long bones is a primary site for lymphocyte production. This process is known as lymphopoiesis and involves the differentiation of hematopoietic stem cells into various lymphocyte types such as B cells, T cells, and natural killer cells.

Explanation

Statement 1 is correct: The femur, or thigh bone is the longest and strongest bone in the human body. It stretches from the hip to the knee and provides crucial support and stability, allowing us to walk, run, and jump. The femur can withstand forces up to 816-1,134 kg before breaking, making it one of the strongest structures in our skeletal system.

Statement 2 is correct: Cholera is a severe bacterial infection caused by Vibrio cholerae. It spreads mainly through contaminated water or food, leading to acute diarrhea and dehydration. In extreme cases a person with can lose up to 20 liters of fluid per day making rapid treatment with rehydration therapy essential.

Statement 3 is incorrect: Athlete’s foot (Tinea Pedis) is not caused by a virus, but by fungal infection. Dermatophyte fungi thrive in warm, damp environments like locker rooms, swimming pools, and sweaty shoes. The infection causes itchy, peeling, and cracked skin between the toes, making it a common concern among athletes and hence the name.

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.

Explanation

The mechanisms of organic evolution refer to the processes by which populations of organisms change over time, leading to the diversity of life forms seen today. These mechanisms explain how species evolve, adapt, and sometimes go extinct. The loss of limbs in snakes is explained by Lamarck’s Theory of Use and Disuse, which suggests that organs that are frequently used develop and strengthen while those that are not used weaken and eventually disappear over generations. Snakes evolved from lizard-like ancestors that originally had limbs. As they adapted to a burrowing or slithering lifestyle, they stopped using their limbs for movement. According to Lamarck’s theory, since the limbs were not used, they gradually reduced in size and eventually disappeared over many generations.

Explanation

Genetics is the study of heredity and variation in living organisms. It explores how traits are passed from parents to offspring through genes which are the units of heredity located on chromosomes.

Option (b) is correct: Pleiotropy occurs when a single gene affects multiple, seemingly unrelated phenotypic traits. Mutations in such a gene can have widespread effects due to its influence on various biological processes This occurs because the gene product (e.g., a protein) may participate in multiple biochemical or physiological pathways. For example, the gene responsible for sickle cell anemia affects multiple traits: red blood cell shape, resistance to malaria, and oxygen transport efficiency.