3.3.2 Gas Exchange Flashcards
FISH:
Explain how the gills allow efficient gas exchange
- The lamellae provide a large surface area
- Thin epithelium so a short diffusion pathway
- Counter-current flow maintains the concentration gradient across whole length of lamellae
FISH:
Explain how the highly folded structures of the gill (lamellae) increase the efficiency of gas exchange
They increase the surface area over which diffusion can take place
FISH:
Describe and explain how the countercurrent system leads to efficient gas exchange across the gills of a fish.
Water and blood flow in opposite directions.
This maintains a concentration gradient across the gill (as there is always a higher concentration of oxygen in the water than blood)
Name the process by which carbon dioxide is removed from a single celled organism
Simple diffusion over the body surface
INSECTS:
Explain how the tracheal system limits the size of the insect
Because it relies on diffusion to bring oxygen to respiring tissues.
If insects were large it would take too long for oxygen to reach the tissues rapidly enough to supply the insects needs
INSECTS:
Give 2 explanations as to why the rate of water loss during gas exchange is very low in most insects.
- Insects have spiracles that can close to reduce water loss
* Insects have sunken spiracles that trap moist air
Describe and explain ways in which plants limit water loss.
- Plants have a waxy cuticle which prevents the evaporation of water;
- Plants have hairs on their surface that trap moist air reducing the water potential gradient
- Plants have sunken stomata which again traps moist air reducing the water potential gradient
- The stomata can close which reduces evaporation
How can you calculate pulmonary ventilation rate?
= tidal volume (dm3) x breathing rate (min-1)
LEAVES:
Explain why less water is lost by a plant when the air is humid.
Humidity reduces the difference in concentration of water between the plant and the air.
Reduced concentration gradient = less water loss
During an asthma attack, less oxygen diffuses into the blood from the alveoli. Explain why.
Asthma attacks narrow the airways, so not as much oxygen reaches the alveoli.
This means that there is a small concentration gradient (between blood and alveoli) so rate of diffusion is lower
What are xerophytes?
Plants that are adapted to living in areas where water is in short supply
Give examples of how xerophytes limit water loss
- Thick cuticle
- Waxy cuticle
- Rolled up leaves
- Hairy leaves
- Stomata in pits or grooves
- A reduced surface area to volume ratio
- Deep roots
- Sunken stomata
XEROPHYTES:
Explain how having rolled up leaves reduces water loss
- Traps a region of still air within the rolled leaf.
- The trapped region has a high water potential.
- As there is no water potential gradient between the inside and outside of the leaf there is no water loss
XEROPHYTES:
Explain how having hairy leaves reduces water loss
- Traps still, moist air next to the leaf surface.
- This reduces the water potential gradient between the inside and outside of the leaf so less water is lost.
XEROPHYTES:
Explain how having stomata in pits or grooves reduces water loss
- It traps still, moist air next to the leaf surface.
- This reduces the water potential gradient between the inside and outside of the leaf so less water is lost.
Explain why water is always lost from the gas exchange surfaces of terrestrial organisms
- Gas exchange surfaces are permeable.
- As there is a higher concentration of water molecules inside the animal than outside water will diffuse out.
Why does every cell inside an insect have a short diffusion distance?
They are only a short distance from the tracheae or the tracheoles
INSECTS:
Name the tiny pores on the body surface of insects
Spiracles
