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

Explanation

The small pouch containing silica gel found in bottles of medicine (tablets or powder) is primarily used to absorb moisture. Silica gel is a desiccant, meaning it has a high affinity for water molecules. It absorbs moisture from the surrounding environment, preventing the tablets or powder from degrading due to humidity. This helps maintain the stability and efficacy of the medicine. Silica gel has a porous structure that traps water molecules through adsorption. Moisture can cause tablets to crumble or powders to clump, reducing their effectiveness and shelf life.

Explanation

Endoscopy is a medical procedure that uses a flexible tube with a light and camera (endoscope) to explore the inside of the body, such as the stomach, intestines, or other organs. The technique relies on the phenomenon of total internal reflection to transmit light through fiber-optic cables inside the endoscope. Total internal reflection occurs when light traveling through a denser medium (such as glass or optical fibers) strikes the boundary with a less dense medium (like air) at a certain angle, causing the light to reflect entirely back into the denser medium instead of refracting out.

Explanation

Option (c) is correct: Formic acid is the substance that many ants inject when they bite. This acid is produced in their venom glands and is responsible for the characteristic pain or burning sensation felt after an ant bite. Formic acid is also used by ants for defense, and some species, like fire ants, use it in larger quantities to cause more intense reactions in their prey or threats.

Option (a), (b) and (d) are incorrect:

Acetic acid is a concentrated form of acetic acid, commonly found in vinegar, but it is not involved in the venom of ants. Methanol is a type of alcohol, not present in ant venom. Stearic acid is a fatty acid commonly found in animal fats and plant oils, but it is not the compound found in ant venom.

Explanation

Option (c) is correct: Eye donation typically involves the donation of the cornea, the transparent, dome-shaped layer at the front of the eye. The cornea is crucial for focusing light on the retina and plays a key role in vision. Corneal transplants are performed to restore vision in people suffering from corneal blindness or damage, which can result from conditions like injury, infections, or diseases.

Option (a), (b) and (d) are incorrect:

The iris controls the amount of light entering the eye by adjusting the size of the pupil. While important for vision, the iris is not typically used in eye donation. The retina is the light-sensitive layer at the back of the eye responsible for sending visual information to the brain. Retinal transplants are highly complex and not commonly done in eye donation. The lens focuses light on the retina but is not commonly donated for transplant.

Explanation

A is matched with 1: Adrenaline, produced by adrenal gland is associated with the body’s response to stress, especially during situations of anger, fear, or danger. It triggers the "fight or flight" response, increasing heart rate, blood pressure, and energy supply. B is matched with 3: Estrogen is indeed the primary female sex hormone that regulates the development of female reproductive tissues and secondary sexual characteristics such as breast development and menstruation. C is matched with 4: Insulin is a hormone that regulates blood glucose levels, facilitating the uptake of glucose by cells for energy. D is matched with 2: Pheromones are chemicals released by animals or humans that influence the behavior of others, particularly related to attracting partners through the sense of smell.

Explanation

A is matched with 3: Atropine is an alkaloid used primarily to dilate the pupil during eye exams or surgeries. It is also used in emergency situations to treat heart trouble, especially in cases of bradycardia (slow heart rate). B is matched with 1: Ether is an anesthetic and was historically used for local anesthesia or as a general anesthetic in surgeries. C is matched with 2: Nitroglycerine is used to treat heart trouble, especially angina (chest pain) by dilating blood vessels and reducing the heart’s workload. D is matched with 4: Pyrethrin is a natural insecticide, derived from chrysanthemums, used for mosquito control and to manage other pests like lice.

Explanation

Royal haemophilia (also known simply as haemophilia) is a sex-linked recessive genetic disorder. It is an X-linked recessive genetic disorder characterized by impaired blood clotting due to deficiencies in clotting factors, primarily Factor VIII (Haemophilia A) or Factor IX (Haemophilia B). It primarily affects males, as the gene responsible for haemophilia is located on the X chromosome. Females can be carriers. Queen Victoria of England was a carrier of haemophilia B and passed the trait to several of her children, including her son Leopold, who died from a hemorrhage after a fall when he was 30.

Explanation

Lathyrism is a neurological disorder caused by the excessive consumption of khesari dal (also known as Lathyrus sativus), a type of legume commonly grown in India and some other regions. The condition is linked to the presence of toxic compounds in the dal, specifically -ODAP (-oxalylamino-L-alanine), which can cause damage to the nervous system, leading to symptoms like paralysis, muscle weakness, and spasticity.

Explanation

A is matched with 4: Hugo de Vries proposed the Mutation Theory in the early 20th century which suggested that new species arise through sudden, discontinuous changes (mutations) in genetic material. B is matched with 3: Darwin>s Theory of Evolution was published in 1859 (On the Origin of Species). It explains evolution through natural selection and gave key concepts include adaptive radiation, survival of the fittest, and descent with modification. C is matched with 1: George Beadle and Edward Tatum proposed the One Gene One Enzyme Hypothesis, which states that each gene is responsible for producing a single enzyme that controls a specific biochemical reaction. D is matched with 2: Jacob and Monod>s Operon Concept was introduced in 1961 which explains how gene regulation in prokaryotes (e.g., lac operon in E. coli). It is key for understanding antibiotic resistance and gene expression.

Explanation

The Tambalacoque tree (Sideroxylon grandiflorum), also known as the Dodo tree, usually relied on the Dodo bird for seed germination. The seeds of this tree required scarification (softening of the seed coat) through the Dodo>s digestive system. The Dodo (Raphus cucullatus), a flightless bird endemic to Mauritius, became extinct in the late 1600s due to over-hunting by humans and the introduction of non-native animals like rats and pigs. After the extinction of the Dodo, natural reproduction of the Tambalacoque tree declined significantly.