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

Explanation

Stem cutting is a common asexual propagation method where a section of the stem, with at least one node and some leaves is cut from a parent plant and rooted to grow a new, genetically identical plant. This method helps maintain desirable plant traits. Bougainvillea, carnations, grapes, and cocoa can all be propagated by stem cuttings. Bougainvillea is propagated using hardwood(during the dormant season) or softwood (during spring/summer from young growth) cuttings depending on the season. Carnations: Stem cuttings taken from side shoots in spring/ summer. Must have two nodes and leaves for successful propagation. Grapes: Dormant hardwood cuttings taken during winter with 3 nodes. Ideal for maintaining grapevine traits. Cocoa: Propagated using young, tender stem cuttings during the rainy season. Cuttings should have at least two nodes and leaves.

Explanation

The mitochondrion is an organelle in the cell that contains its own DNA. Unlike most of the cell’s DNA, which is found in the nucleus, mitochondria have their own small circular DNA. This mitochondrial DNA (mtDNA) encodes essential proteins involved in energy production through cellular respiration. Mitochondria are often referred to as the "powerhouses of the cell" due to their role in ATP synthesis. Options (a), (b) and (c) are incorrect:

Golgi Apparatus: Membrane-bound organelle; modifies, sorts, and packages proteins and lipids; consists of cisternae; involved in glycoprotein and glycolipid formation. Lysosomes: Membrane-bound vesicles; contain hydrolytic enzymes; digest carbohydrates, proteins, lipids, nucleic acids; play role in intracellular digestion; known as "suicide bags" due to potential self-digestion. Centrioles: Cylindrical structures; composed of microtubules; organize microtubules during cell division; form mitotic spindle; located near nucleus in animal cells; do not contain DNA.

Explanation

Athlete’s Foot, medically known as tinea pedis, is a fungal infection caused by a group of fungi called dermatophytes, which thrive in warm, moist environments like those found in shoes. It primarily affects the skin of the feet, causing itching, redness, and scaling. It is highly contagious and spreads through direct contact or contaminated surfaces. Options (a), (c) and (d) are incorrect:

Bacterial infections are caused by microorganisms like Staphylococcus or Streptococcus. These can lead to conditions like pneumonia, tuberculosis, and food poisoning. Unlike fungal infections, bacterial infections can usually be treated with antibiotics. Protozoans are single-celled organisms that can cause diseases like malaria (caused by Plasmodium), amoebic dysentery (caused by Entamoeba histolytica), and sleeping sickness (caused by Trypanosoma). They are typically transmitted through contaminated water or insect bites. Nematodes, or roundworms, are parasitic worms that can infect humans, causing diseases like ascariasis, filariasis, and hookworm infection. These are usually transmitted through contaminated soil or food.

Explanation

Epiphytes, commonly known as "air plants," are plants that depend on other plants primarily for mechanical support. They grow on the surface of other plants (like trees) to access better light and air circulation, but they do not take nutrients from the host plant. While they do not parasitize the host but they can absorb water and nutrients from rain, dew, and air humidity through specialized structures like spongy roots. Epiphytes are typically found in humid environments and include species like orchids, mosses, and ferns. They do not rely on the host for food or shade, as they can photosynthesize and derive most of their nutrients from the air and rain.

Explanation

Blue-green algae, also known as cyanobacteria are often used as biofertilizers in rice cultivation. They have the ability to fix atmospheric nitrogen into a form that plants can use, enriching the soil with nitrogen and improving crop growth.

Explanation

A phytotron is a facility that provides an environment where various environmental factors such as temperature, humidity, light, and CO₂ levels can be controlled precisely to study plant growth and development. This setup helps scientists to conduct experiments on plants in a controlled and reproducible environment. Phytotron is neither related with growing plants in disease free conditions nor conserving endangered species of plants.

Explanation

Soft drinks, especially colas, often contain caffeine, which is a stimulant. Caffeine can help to increase alertness and reduce fatigue, and it is commonly added to colas and other energy drinks.

Explanation

Canola oil is derived from a type of mustard plant that has been specially bred to have very low levels of erucic acid, which is a substance that can be harmful in large amounts. This makes canola oil safe and suitable for human consumption. Canola oil is known for being rich in unsaturated fatty acids, especially omega-3 and omega-6 fatty acids, making it a heart-healthy cooking oil. It has a long shelf life due to its stability, and its mild flavor makes it suitable for a variety of culinary uses.

Explanation

Mycorrhiza is a symbiotic association between fungi and the roots of higher plants. In this relationship, the fungi help the plants by increasing water and nutrient absorption (especially phosphorus), while the plants provide carbohydrates (like glucose) to the fungi. This mutualistic relationship is beneficial to both organisms and plays a crucial role in plant growth and soil health.

Explanation

Ergotism is historically known as "St. Anthony’s Fire" is directly linked to the consumption of grains (such as rye, barley, wheat, and oats) contaminated with the ergot fungus (Claviceps purpurea). The fungus infects the grains, producing sclerotia (ergot bodies) that contain toxic alkaloids. These alkaloids can cause two forms of ergotism:

Convulsive ergotism which is cracterized by seizures, hallucinations, and muscle spasms. Gangrenous ergotism which leads to restricted blood flow, causing tissue death and gangrene in extremities.