Gas exchange in single-celled organisms and insects Flashcards
How has insect adapted for efficient gas exchange?
1) Air moves into the trachea through pores on the surface called spiracles.
2) Internal network of tubes - tracheae.
- The tracheae are supported by strengthening rings to prevent them from collapsing.
3) The tracheae divide into smaller dead-end tubes called tracheoles.
- Tracheoles extend throughout the whole body tissues of the insect and they have thin, permeable walls that go to each cell.
Through those features, the oxygen in the air can directly enter the respiring tissues, as there’s a short diffusion pathway from tracheole to any body cell.
How do respiratory gases move in and out of the tracheal system through diffusion gradient?
Along a diffusion gradient - When cells are respiring, it uses up the oxygen so the concentration at the end will fall. This creates a diffusion gradient that will allow oxygen to diffuse from the air into the trachea and tracheoles and to the cells.
CO2 is produced by cells during respiration will create a diffusion gradient in the opposite direction so CO2 will diffuse out through the tracheoles to the trachea.
Diffusion in the air is quicker than in water so gases can be exchanged quickly.
How do respiratory gases move in and out of the tracheal system through mass transport?
The contraction of the muscles can squeeze the trachea which allows mass movements of air in and out which speeds up the exchange of respiratory gases.
How do respiratory gases move in and out of the tracheal system through the ends of tracheoles?
The ends of the tracheoles are filled with water.
When it’s during a period of major activities, muscle cells around the tracheoles carries out some anaerobic respiration (lactic acid). This produces lactate (lactic acid) which is soluble therefore it lowers the water potential of the muscle cells.
Water will move into the muscle cells through tracheoles by osmosis. So the volume of water in the tracheoles will decrease and by doing so, it draws in the air (as volume decrease, pressure increase).
This increases the rate of air drawn in but also leads to greater water evaporation.
How do spiracles affect water loss?
- Spiracles can open and close by a valve.
- When it’s open, water vapor can evaporate from the insect.
- Most of the time, they are closed to prevent water loss but then need to be open to allow gas exchange.
What are the limitations of the tracheal system?
It relies on the gas exchange between the environment and the cells.
Also for the diffusion to be effective, the diffusion pathway must be short so insects are small in size which limits the size which an insect can attain.
How do insects prevent water loss?
- Close their spiracles using muscles.
- Have a waterproof, waxy cuticle all over their body and tiny hairs around their spiracle to reduce evaporation.
