Question Bank [2022] — BIOLOGY STD 12 Science — Question

Definition: Adaptation is an attribute of the organism (morphological, physiological, and behavioural) that enables the organism to survive and reproduce in its habitat.

i. Adaptations of plants for aquatic and desert habitats:

a. Adaptations of plants for aquatic habitats:

1. Leaves and stem of some aquatic plants show presence of aerenchyma tissue which helps in exchange of gases between plant organs above the water surface and submerged plant organs.
2. Many aquatic plants have flat leaves to receive maximum sunlight for photosynthesis. Leaves of submerged plants are often dissected to minimize water resistance.

b. Adaptations of plants for desert habitats:

1. Many desert plants have a thick cuticle on their leaf surfaces and have their stomata in deep pits to minimize loss of water through transpiration.
2. They show a special photosynthetic pathway (CAM - Crassulacean Acid Metabolism) that enables their stomata to remain closed during daytime.