Limiting Water Loss Flashcards
What is the problem for terrestrial organisms such as insects in limiting water loss?
Water easily evaporates from the surface of their bodies and so they can become dehydrated.
How does an insects small SA to Vol ratio reduce water loss?
Minimises area over which water is lost.
How does an insects waterproof covering reduce water loss?
Rigid outer skeleton of chitin covered with a waterproof covering, over their body’s surface.
How does an insects spiracles of the tracheae reduce water loss?
Openings of tracheae at body surface which can be closed to reduce water loss, conflicts with needs for oxygen so occurs mainly when insect is at rest.
How doe terrestrial leaves limit water loss?
Waterproof covering over leaves and ability to close stomata.
Why are leaves unsuited for limiting water loss?
They need a large SA to vol ratio for diffusion of gases for photosynthesis.
What have plants with restricted water supply adapted?
Transpiration, known as xerophytes. These are plants living in areas of short water supply.
How does leaves thick cuticle reduce water loss?
Waxy cuticle forms a waterproof barrier. Thicker the cuticle, less water can escape.
How does rolling of leaves reduce water loss?
Protects lower epidermis, where stomata are, from the outside. Traps a region of still air within the rolled leaf, becomes saturated with water and so has a very high water potential.
How does hairy leaves reduce water loss?
Traps still moist air next to leaf surface, Water potential gradient is reduced, limiting water loss.
How does stomata in pits or grooves of leaves reduce water loss?
Trap still moist air to reduce water potential gradient.
How does a reduced SA to vol ratio of leaves limit water loss?
Smaller and rounder leaves reduces rate of water loss. Reduction in surface area against need for sufficient SA for photosynthesis is balanced.
