Gas Exchange in Single - Celled Organisms + Insects Flashcards
Why can’t single - celled organisms rely on diffusion for gas exchange?
They have a large surface area to volume ratio, allowing efficient diffusion across their body surface
How do single - celled organisms absorb oxygen?
By diffusion across their body surface, which is covered only by a cell - surface membrane
Does the presence of a cell wall in single - celled organisms hinder gas exchange?
No, the cell wall does not act as a barrier to the diffusion of gases
How is carbon dioxide removed from single - celled organisms?
It diffuses out across the body surface as a waste product of respiration
Why do terrestrial insects need adaptations to conserve water?
A large surface area for gas exchange increases water loss through evaporation, creating a conflict between gas exchange and water conservation
What internal structures have insects evolved for gas exchange?
An internal network of tubes called tracheae
Why do insect tracheae have strengthened rings?
To prevent them from collapsing
What do the tracheae divide into?
Smaller, dead - end tubes called tracheoles
How do tracheoles help deliver oxygen to insect tissues?
They extend throughout all body tissues, bringing oxygen directly to respiring cells
Why is diffusion in insects efficient?
The short diffusion pathway between tracheoles and body cells allows rapid gas exchange
What are the three ways respiratory gases move in and out of the tracheal system in insects?
1/ Along a diffusion gradient
2/ By mass transport
3/ By the water at the ends of tracheoles
How does a diffusion gradient help gas exchange in insects?
1/ Oxygen is used up in respiration, lowering its concentration at the ends of tracheoles
2/ This creates a diffusion gradient causing oxygen to diffuse from the atmosphere into the tracheoles and cells
3/ Carbon dioxide, produced in respiration, creates a diffusion gradient in the opposite direction diffusing out of the tracheoles to the atmosphere
Why is diffusion in insects rapid?
Diffusion in air is much faster than in water, allowing quick gas exchange
How does mass transport aid gas exchange in insects?
The contraction of muscles squeezes the trachea, causing mass movement of ain in and out, speeding up gas exchange
What happens to the water at the ends of the tracheoles during major activity?
1/ Muscle cells respire anaerobically, producing lactate
2/ The lactate lowers the water potential of the muscle cells
3/ Water moves from the tracheoles into the muscle cells by osmosis
4/ This draws air deeper into the tracheoles, increasing the rate of diffusion
Why does removing water from tracheoles speed up diffusion?
The final diffusion pathway occurs in a gas rather than a liquid phase, which increases the rate of oxygen diffusion
What is the trade - off of water removal from the tracheoles?
It increases water evaporation, leading to greater water loss from the insect
