Write the structural formula of the two isomers of butane.

Describe briefly any five kinds of irrigation systems developed to supply water to agricultural lands?

• Surface Irrigation: This is the most common method where water flows over the soil surface and infiltrates into the soil. It includes furrow, basin, and flood irrigation techniques.
• Drip Irrigation: A highly efficient method that delivers water directly to the roots of plants through a network of tubing and emitters, minimizing evaporation and runoff.
• Sprinkler Irrigation: Involves using a system of pipes to distribute water through a series of overhead sprinklers, simulating rainfall over the crop area.
• Subsurface Irrigation: Similar to drip irrigation, but the water is delivered below the soil surface, providing moisture directly to the root zone and reducing evaporation.
• Center Pivot Irrigation: A mechanized system that rotates around a pivot point, allowing for the controlled application of water over large fields in a circular pattern.

Briefly explain the ecological pyramid which is always upright.

An oligotrophic lake is characterised by

• A. great changes in water level
• B. Long food chains
• C. Low nutrient and little life
• D. High nutrient levels and abundant flora and fauna

An allele is described as ‘dominant’ if it expresses itself when it occurs in

• A. Heterozygous condition
• B. Homozygous condition
• C. Both heterozygous condition and homozygous conditions
• D. Hemizygous condition

Which of the following is not an example of natural polymer?

• A. Wool
• B. Silk
• C. Leather
• D. Nylon