1What are the two major adaptations of gas exchange surfaces?
Large surface area, thin layer of cells
2What does a short diffusion pathway provide?
Efficient gas exchange
3What maintains a steep concentration gradient?
Gas exchange surfaces
4How do single-celled organisms exchange gases?
Diffusion through their outer surface
5Why can single-celled organisms rely on diffusion?
Large surface area to volume ratio
6What is the counter-current system in fish used for?
Efficient gas exchange
7Why is counter-current flow effective?
Maintains a concentration gradient
8How does water flow over fish gills?
Through the lamellae
9What are lamellae?
Thin plates on gill filaments
10What increases surface area in fish gills?
Lamellae and filaments
11What do insects use for gas exchange?
Tracheae
12What are spiracles?
Pores on an insect's surface
13How do insects maintain a diffusion gradient?
Through muscle movement
14What controls water loss in insects?
Closing spiracles and waxy cuticles
15Why are hair-covered spiracles important?
Reduce water loss
16What do dicotyledonous plants exchange gases for?
Photosynthesis and respiration
17Where does gas exchange occur in plants?
Mesophyll cells in leaves
18What controls the opening of stomata?
Guard cells
19Why do plants close stomata?
To reduce water loss
20What do xerophytes have to reduce water loss?
Waxy cuticles and sunken stomata
21Why are stomata in pits helpful?
Trap moist air
22What reduces the concentration gradient in xerophytes?
Hairs and rolled leaves
23What is the function of curved leaves?
Protect stomata from wind
**Exam Questions**
24How are gas exchange surfaces adapted for diffusion?
Large surface area, thin layer
25Why do fish use a counter-current system?
To maintain a concentration gradient
26How do desert plants reduce water loss?
Sunken stomata, rolled leaves