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

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.