Gas Exchange In Single-celled Organisms And Insects Flashcards
What type of SAV do single-celles organisms have?
They have a large surface area to volume ratio.
Why do single celled organisms have large surface area to volume ratio?
Because they are small.
How do oxygen and carbon dioxide move across the body surface?
By simple diffusion across the body-surface which is covered only by cell-surface membrane and.
Does the cell wall act as a barrier to the diffusion of gases?
No
Do insects have mechanisms to conserve water?
Yes
What two things do insects need to balance?
Water conservation and gas exchange.
Why does the increase in surface area for gas exchange conflict with conserving water?
Water will evaporate from it which will cause what a loss.
What is the name of the internal network of tubes in insects for gas exchange?
Tracheae
What are the tracheae supported by?
Strengthened rings to prevent them from collapsing.
What did the tracheae divide into?
Smaller dead-end tubes called tracheoles .
Where do the tracheoles extend throughout?
They extend throughout the body tissue of the insect.
What is brought directly to the respiring tissues?
Atmospheric air with oxygen.
Is there a short diffusion pathway along diffusion pathway from a tracheole to any body cell?
There is a short diffusion pathway.
What are the three ways in which respiratory gases move in and out of the tracheal system?
Along a diffusion gradient;
Mass transport;
The end of the tracheoles are filled with water
What is used up when cells respire?
Oxygen
Why does the oxygen concentration fall towards the end of the tracheoles?
The oxygen is used up during respiration.
Do oxygen and carbon dioxide have diffusion gradients in the same direction?
No this is because carbon dioxide is produced by cells during respiration so the gaseous carbon dioxide defuses along the tracheoles and the tracheae from the cells to the atmosphere whereas oxygen goes from the atmosphere to the cells.
What enables mass movements of the air in and out of the insect trachea?
The contraction of muscles in insects.
What further speeds up the exchange of respiratory gases?
The contraction of muscles.
What happens during periods of major activity?
The muscle cells around the tracheoles respire and carry out some anaerobic respiration which produces lactate.
What does the lactate do?
It lowers the water potential of the muscle cells so water is drawn into them by osmosis which draws more air into the tracheae.
Is the final diffusion stage liquid or gas?
Gaseous
What is an advantage of gaseous gas exchange?
It speeds up diffusion.
What is a disadvantage of the final diffusion pathway being gaseous?
Leads to greater water evaporation.
How do gases enter and leave the insects?
Through pores called spiracles on the body surface.
How are the spiracles opened and closed?
By a valve.
What can the water do when the spiracles are open?
The water can evaporate from the insect.
Why do insects open their spiracles?
To allow gas exchange.
Why are insects so small?
They have to have a short diffusion pathway for gas exchange.
