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

Explanation

Statement 1 is incorrect: Dengue is not caused by a protozoan but by the dengue virus (DENV), of the Flaviviridae family. The virus spreads through bites from infected Aedes mosquitoes, primarily Aedes aegypti and Aedes albopictus.

Statement 2 is incorrect: Retro-orbital pain, which refers to pain behind the eyes, is a common symptom of dengue fever. Patients often experience severe headache accompanied by retro-orbital pain during the febrile phase of the illness.

Statement 3 is correct Many dengue patients experience a skin rash, which usually appears a few days after the fever starts. Some people even develop a "white islands on a red sea" rash, where parts of the skin turn white amid the redness. Nosebleeds (epistaxis) and bleeding gums, are common in dengue patients particularly in severe forms like dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS).

Explanation

Foot and mouth disease (FMD) is a highly infectious viral disease that affects cloven-hoofed animals, including cattle, sheep, goats, and pigs. It is caused by the foot-and-mouth disease virus (a member of the Picornaviridae family). The disease spreads rapidly through direct contact, contaminated feed, or aerosols. Anthrax is a severe bacterial disease caused by Bacillus anthracis. It primarily affects cattle, sheep, and goats, but can also infect humans through spores present in contaminated soil, water, or feed. Symptoms include sudden death, high fever, difficulty breathing, and bleeding from body openings. The disease is zoonotic, meaning it can spread from animals to humans. Black Quarter, also known as Blackleg, is an infectious bacterial disease caused by Clostridium chauvoei. It mainly affects young cattle and sheep which results in painful swelling of muscles, fever, lameness, and rapid death due to toxin production. The disease spreads through ingestion of spores present in soil, which activate under favorable conditions. Cowpox is an infectious viral disease caused by the cowpox virus, which belongs to the Orthopoxvirus family. It primarily affects cattle but can also infect humans. The virus is transmitted through direct contact with infected animals or contaminated materials.

Explanation

The process of conversion of complex food substances to simple absorbable forms is called digestion and is carried out by our digestive system by mechanical and biochemical methods. Assertion A is False: Protein digestion is not limited to the small intestine alone. Protein digestion begins in the stomach, where the enzyme pepsin breaks down proteins into smaller peptides. The process continues in the small intestine, where pancreatic enzymes (like trypsin and chymotrypsin) and intestinal enzymes (like peptidases) further break down peptides into amino acids. Reason R is True: The pancreas secretes several protein-digesting enzymes such as trypsin, chymotrypsin, and carboxypeptidase into the small intestine. These enzymes play a crucial role in breaking down proteins into smaller peptides and amino acids.

Explanation

Reproduction is the process by which organisms produce offspring. It ensures the continuation of a species. There are two main modes of reproduction:

Asexual Reproduction involves a single parent and produces offspring that are genetically identical to the parent. Examples include binary fission (in bacteria), budding (in yeast), and parthenogenesis (in some insects). Sexual Reproduction involves two parents (usually of different sexes) and combines genetic material from both parents to create offspring with unique genetic variations. Examples include fertilization in animals and pollination in plants. Assertion A is True: Amoeba, a unicellular protozoan reproduces asexually through binary fission, a process where the parent cell divides into two genetically identical daughter cells. Process of Binary Fission in Amoeba:

Growth Phase: The Amoeba increases in size, accumulating nutrients required for division. Nuclear Division (Mitosis): The nucleus undergoes mitotic division, ensuring that both daughter cells receive an identical set of genetic material. Cytoplasmic Division: The cytoplasm divides, creating two separate daughter cells. Formation of Two New Amoebae: Each daughter cell becomes independent and grows into a mature Amoeba. Reason R is True: Asexual reproduction is common among single-celled organisms, and in plants and animals with relatively simple organisations. Reason R is the correct explanation of Assertion A, since, Amoeba is a unicellular organism and all unicellular organisms reproduce asexually. (Note: Some unicellular organisms are capable of sexual reproduction, such as conjugation in ciliates like Paramecium, where two cells exchange genetic material. Additionally, some unicellular fungi, like yeasts, can undergo both asexual reproduction (such as budding) and sexual reproduction (like mating and meiosis) Fig.: Binary fission in Amoeba

Explanation

Assertion (A) is true: Diabetes insipidus(DI) is a condition characterized by the inability to properly regulate water balance in the body. It leads to excessive urination (polyuria) and dehydration. As a result, individuals with DI often experience intense thirst (polydipsia) to compensate for the excessive water loss. Reason (R) is false: Diabetes insipidus is caused by either insufficient secretion of vasopressin (antidiuretic hormone) or the kidneys’ inability to respond to vasopressin. Excess secretion of vasopressin is not associated with DI. Excess secretion of vasopressin would lead to water retention, not excessive thirst. Thus, the Assertion A is true but the Reason R is false.

Explanation

Workers in the coal mining industry are most affected by pneumoconiosis. Pneumoconiosis is a lung disease caused by the inhalation of dust, particularly mineral or industrial dust over a prolonged period. It primarily affects workers in industries where they are exposed to high levels of airborn e particles. Coal workers’ pneumoconiosis (CWP), also known as black lung disease, is caused by prolonged inhalation of coal dust, making coal miners the most affected group. Other forms of pneumoconiosis include silicosis (caused by silica dust, affecting quarry and glass industry workers) and asbestosis (caused by asbestos exposure).