Explanation

• Igneous rocks can transform into metamorphic rocks under heat and pressure.
• Sedimentary rocks also become metamorphic when subjected to metamorphic conditions.

Additional information:

• Examples: Marble (from limestone), Slate (from shale)
• Uses: Construction, decoration, sculptures

Explanation

• Tree circle (tree ring) counting) gives a historical timeline for soil formation.
• Soil development is often linked to age of surrounding vegetation.

Additional information:

• Importance: Helps determine fertility and suitability for crops

Last verified on 25-01-2026

Explanation

• LD50 (Lethal Dose 50%) is the dose that kills half of the test population.
• It is a standard measure to assess toxicity of substances.

Additional information:

• ED50: Effective dose for 50% population (not lethal)
• LC50: Lethal concentration in environment (e.g., water, air)
• Used in risk assessment and pesticide regulation

Last verified on 25-01-2026

Explanation

• Cutworms feed on young maize seedlings, often cutting them at the soil level.
• They are most destructive in the early stages of crop growth.

Additional information:

• Stem borer → attacks stems at later stages
• Aphid → sucks sap, spreads viral diseases

Last verified on 25-01-2026

Explanation

• DAP (Di-Ammonium Phosphate) is a common fertilizer for onions.
• 3–4 bags per acre is recommended by agricultural research centers for optimal onion growth.

Additional information:

• Application timing: At sowing and early growth stages

Last verified on 25-01-2026

Explanation

• Loamy soil is a balanced mixture of sand, silt, and clay.
• It has good water retention, drainage, and nutrient content, ideal for wheat.

Additional information:

• Sandy soil → drains quickly, low nutrients
• Clay soil → waterlogged, poor aeration

Last verified on 25-01-2026

Explanation

• Eli Whitney invented the cotton gin in 1794 to speed up cotton processing.
• It dramatically increased cotton production and supported the textile industry.

Additional information:

• Impact: Boosted cotton exports from the USA

Last verified on 25-01-2026

Explanation

• Cotton, wheat, and rice use the C3 photosynthetic pathway.
• In C3 plants, the first stable product of photosynthesis is 3-carbon compound (3-PGA).

Additional information:

• Examples of C4 plants: Maize, sugarcane, sorghum, millet
• Key enzyme in C3 plants: RuBisCO

Last verified on 25-01-2026

Explanation

• A region where total rainfall is less than evapotranspiration is classified as a Desert.

Additional information:

Examples of desert regions:

• Sahara Desert – Africa
• Thar Desert – Pakistan/India
• Arabian Desert – Middle East
• Gobi Desert – China/Mongolia
• Kalahari Desert – Africa

Last verified on 24-01-2026

Explanation

• Soil water-holding capacity refers to the ability of soil to retain water for plants.
• Clay soil has very fine particles.
• It can hold the most water.

Additional information:

Water-holding capacity of soils (approximate):

• Clay – 40–60%
• Silt – 30–50%
• Loam – 25–40%
• Sandy soil – 5–15%
• Peaty soil – 50–80%

Last verified on 24-01-2026