Limiting water loss

Problems in insects:

• Most insects are terrestrial
• Water easily evaporates from the surface of their bodies and they become dehydrated
• Although efficient gas exchange surfaces require a thin, pemeable surface with a large area, this conflicts with the need to conserve water

Evolved the following adaptations that reduce water loss:

Small surface area to volume ratio -

• To minimise the area over which water is lost

Waterproof coverings -

• Over their bodies and surfaces
• Is a rigid outer skeleton of chitin that is covered with a waterproof cuticle

Spiracles -

• Are the openings of the trachea at the body surface
• Can be closed to reduce water loss
• Conflicts with the need for oxygen, so happens largely when the insect is at rest

These features mean that insects cannot use their body surface to diffuse respiratory gases in the way a single-celled organism does. Instead they have an international network of tubes called trachea that carry air containing oxygen directly to the tissues.

Problems in plants:

• While plants also have waterproof coverings, they cannot have a small surface area to volume ratio beacuase they photosynthesise

Reduce water loss by:

Having…