Explanation: Ecology is a branch of biology that deals with the relationships of living organisms with one another and with their physical surroundings. It examines how organisms adapt to their environment, how energy flows through ecosystems, and how matter cycles within the biosphere. The term “Ecology” was first coined by Ernst Haeckel in 1866.

Explanation: Bullets are typically made of lead or lead alloys because lead is dense and malleable. When bullets remain lodged in the body, they can corrode over time and release lead ions into surrounding tissues and blood, resulting in chronic lead poisoning (plumbism). Symptoms include abdominal pain, anemia, fatigue, headache, irritability, and neurological disorders. In severe cases, it may cause kidney and brain damage.

Prevention: Complete removal of bullet fragments and regular monitoring of blood lead levels in affected individuals are essential to prevent toxicity.

Explanation: The gas used for artificial ripening of green fruits is ethylene (C₂H₄). Ethylene is a natural plant hormone that regulates fruit ripening by stimulating the conversion of starches into sugars, making the fruit softer and sweeter. In artificial ripening, ethylene gas is introduced in controlled amounts to uniformly ripen fruits such as bananas, mangoes, and tomatoes. However, the use of harmful chemicals like calcium carbide for ripening is banned because it produces toxic substances like acetylene.

Explanation: A rainbow is formed in the part of the sky opposite to the Sun. It occurs when sunlight is refracted, internally reflected, and dispersed by raindrops, splitting the light into its seven constituent colors. The observer must have the Sun behind them and rain in front to see the rainbow clearly.

Explanation: Nitrogen is an essential nutrient for plants, used in the synthesis of amino acids, proteins, nucleic acids, and chlorophyll. Plants absorb nitrogen from the soil primarily in the inorganic forms of nitrate (NO₃⁻) and nitrite (NO₂⁻). Urea, when applied as fertilizer, is first converted by soil bacteria into ammonia (NH₃) and then into nitrates through nitrification before being absorbed by roots.

Key Steps:

• Ammonification: Conversion of organic nitrogen (from dead plants/animals) into ammonia.
• Nitrification: Conversion of ammonia into nitrites and then nitrates by bacteria like Nitrosomonas and Nitrobacter.
• Assimilation: Uptake of nitrates by plants to form amino acids and proteins.

Explanation: The main cause of global warming is the rise in the concentration of carbon dioxide (CO₂) and other greenhouse gases in the atmosphere. These gases trap heat radiated from the Earth’s surface, creating the greenhouse effect and leading to an overall increase in the planet’s temperature.

Explanation: The term LASER stands for Light Amplification by Stimulated Emission of Radiation. A laser produces a highly coherent, monochromatic, and intense beam of light by amplifying light through the process of stimulated emission. In this process, atoms or molecules in an excited state emit photons in phase with incoming photons, resulting in a strong, directed beam. Lasers are widely used in medicine, communication, industry, defense, and scientific research.

Explanation: Marijuana is a psychoactive drug obtained from the female inflorescence (flowering tops) of the Cannabis sativa plant. It contains the active compound tetrahydrocannabinol (THC), which affects the central nervous system and alters mood and perception.