Gas exchange in insects
Most adult insects are terrrestrial, they live on land. The water evaporates from their bodies and they run the risk of dehydration. However, efficient gas exchange requires a thin, permable surface with a large surface area and this conflicts with the need to convserve water.
Terrestrial organisms have a waterproof layer to cover the body surface. e.g. exoskeleton of insects - ridig and has a thin waxy layer and a thicker layer of chitin and protein.
Insects have a small surface area to volume ratio so couldn't use their body surface for gas exchange, therefore gas exchange takes place through paired holes called spiracles. The spiracles run along the side of the body and lead into tubes called tracheae which are lined with chitin. These then branch into smaller tubes called tracheoles.
Spiracles are able to open and close so gas exchange can take place and also water loss can be reduced. Some insects have hairs covering the spiracles which prevent solid particles from getting in. When they're resting diffusion takes place through spiracles, tracheae and tracheoles. During activity the movements of the abdomen ventilate the tracheae.
The ends of the tracheoles are close to muscle fibres and filled with fluid, this is where gas exchange takes place. Oxygen dissolves into the fluid and diffuses directly into the muscle cells. No respiratory pigment of blood circulation is required and carbon dioxide diffuses out by the reserve process.
Gas exchange in plants
During the day:
- Plants respire
- They photosynthesise during the day
- Some of the carbon dioxide needed for photosynthesis is provided by respiration and the rest diffuses from the atmosphere into the leaves
During the night…