Xerophytes

Question 1

describe adaptions insects have evolved to conserve water

Answer 1

• small surface area to volume ratio to minimise the area over which water is lost
• waterproof coverings over their body surfaces, insects have a rigid outer skeleton made from chitin that is covered with a waterproof cuticle
• spiracles opening of tracheae at the body surface that can be closed to reduce water-loss. only occurs when insect is at rest to prevent lack of oxygen

Question 2

describe the adaptions that plants have evolved to conserve water

Answer 2

• a thick cuticle the thicker the cuticle the less water than can evaporate through
• rolling up of leaves stomata are predominantly on the lower epidermis of leaves, the rolling of leaves traps a layer of air within, the air becomes saturated with water vapour meaning there is a very high water potential. this ensures no water potential gradient so no water loss from the leaves.
• hairy leaves a thick layer of hair on the leaves traps moist air next to the leaf surface and reduces the water potential gradient
• stomata in pits or grooves same as hairy leaves
• reduced SA:V ratio leaves a reduced surface area means less water can be evaporated

Question 3

what’s a complication with plants and water loss?

Answer 3

whilst plants can have waterproof coverings, they cannot have a small surface area to volume ratio.
- this is because they have to photosynthesise