Water Availability

Edexcel A-level BiologyThe Nature of EcosystemsLesson 14 of 39

All organisms need water. It is the medium for metabolic reactions, a reactant in photosynthesis and a solvent for transport, and in plants it keeps cells turgid for support. Water availability depends on rainfall, evaporation and drainage and, for animals, on access to drinking water or water in food.

Plants. When water is short, stomata close to reduce water loss. This also reduces carbon dioxide uptake, so photosynthesis and growth slow. If water loss continues, cells lose turgor and the plant wilts. Xerophytes are plants adapted to dry conditions, such as cacti and marram grass. Their adaptations include:

More in The Nature of Ecosystems

• Case Study: Sand Dune Succession
• Light
• Temperature
• Wind and Water Currents
• Oxygen Availability
• Edaphic Factors
• Predation
• Finding a Mate

All 39 lessons in The Nature of Ecosystems · All Edexcel A-level Biology topics