Features that make a good gas exchange system also increase water loss.
Terrestrial organisms must limit water loss without compromising the effectiveness of their gas exchange systems.
E.g. insects have waterproof covering and a relatively small surface area to volume ratio.
Plants have waterproof coverings but can't have small surface area to volume ratio - they must photosyntesise - needs large surface area to capture light and exchange gases.
Ability to close stomata and waterproof coverings are enough for plants that can obtain enough water from soil.
Plants that don't have plentiful water supplies develop other adaptions to limit water loss through transpiration = xerophytes.
Xerophytes - plants adapted to live in areas where water loss from transpiration may exceed water uptake.
Without adaptions plants would die.
Main way to surface unfavourable water balance = to reduce rate at which water is lost by transpiration:
- A thick cuticle - wacy cuticle forms waterproof barrier, the thicker the cuticle, the less water can escape by transpiration. E.g. Holly and other evergreen plants have thick cuticles - reduces water loss during winter when water is difficult to absorb from frozen soil.
- Rolling up of leaves - leaves have stomata largely or entirely…