Desert Adaptations
- Hot deserts pose three main challenges: extreme heat, scarce water, and nutrient-poor soils.
- lants and animals have evolved adaptations for water conservation, temperature regulation, and efficient use of limited resources.
The Saguaro Cactus (Carnegiea gigantea)
- Water Storage and Collection
- Thick, fleshy stem can store large amounts of water from rare rains.
- Wide-spreading root system plus a deep taproot ensure maximum water uptake.
- Minimizing Water Loss
- Thick waxy cuticle reduces transpiration.
- Spines instead of leaves lower surface area and deter herbivores.
- Temperature Regulation
- Vertical stem orientation reduces midday sun exposure.
- CAM photosynthesis: Stomata open at night to conserve water.
- Structural Adaptations
- Pleated stem expands for water storage and contracts in drought without damage.
The Fennec Fox (Vulpes zerda)
- Avoiding Heat
- Nocturnal: Hides in cool dens by day, active at night.
- Large ears radiate body heat, aiding cooling.
- Insulation and Protection
- Thick fur insulates against daytime heat and cold nights.
- Pale coat reflects sunlight.
- Adaptations for Movement
- Hair-covered footpads protect from scorching sand.
- Water Conservation
- Gains most water from food, minimizing need for free water sources.
- Minimizing Water Loss
- The cactus has a $thick waxy cuticle$ covering its epidermis, reducing water loss through transpiration.
- Its leaves are reduced to $spines$, minimizing surface area for water loss and deterring herbivores.
Large surface areas, such as the fennec fox’s ears, are common adaptations for heat dissipation in desert animals.
Tropical Rainforest Adaptations
- Tropical rainforests have high temperatures, heavy rainfall, and dense canopies, creating intense competition for light.
- Organisms adapt to nutrient-poor soils, abundant rainfall, and limited light on the forest floor.
The Yellow Meranti (Shorea faguetiana)
- Competition for Sunlight
- Grows over 100 meters tall to outcompete neighbors for light.
- Support Structures
- Buttressed trunk stabilizes in shallow, rainforest soils.
- Smooth bark sheds rainwater quickly, preventing fungal growth.
- Efficient Water Management
- Broad leaves with drip tips shed excess rainwater, reducing rot or mildew.
- Evergreen foliage capitalizes on year-round photosynthesis.
The yellow meranti is one of the tallest tree species in the world, reaching heights comparable to a 30-story building.
