Gas exchange Flashcards
What is a gas exchange surface?
A boundary between the outside environment and the internal environment of an organism
What features do gas exchange surfaces have to increase the rate of diffusion?
Large surface area
Thin
Why is it beneficial for the organism to have a thin gas exchange surface?
Creates a short diffusion pathway
What does the organism need to maintain in order to increase the rate of diffusion?
Steep concentration gradient
Why don’t single celled organisms need a specialised gas exchange system?
They have a short diffusion pathway so the oxygen can take part in biochemical reactions as soon as it diffuses into the cell
What are the thin plates on the gills of a fish called?
Gill filaments
How do gill filaments benefit the rate of diffusion?
They give a large surface area which increases the rate of diffusion
What covers gill filaments?
Lamellae
What do lamellae have which increase the rate of diffusion?
They have lots of blood capillaries and a thin surface layer of cells
What is the counter-current system?
The blood flows through the lamellae in one direction and water flows over them in the opposite direction
How is the counter-current system effective for diffusion?
The water with a high concentration of oxygen always flows next to the blood with a low concentration of oxygen
This creates a steep concentration gradient which is maintained across the whole length of the gill filament
What is the main gas exchange surface of a plant?
Mesophyll cells
How are mesophyll cells adapted for their role in diffusion?
Large surface area
How do gases move in and out of the leaf?
Through the epidermis
What controls the opening and closing of the epidermis?
Guard cells
What do insects use for gas exchange?
Microscopic air filled pipes called tracheae
What does the air move into the insect through?
Pores on their skins surface called spiracles
Where does the oxygen flow in an insect?
Down the concentration gradient towards the cell
What do the tracheae branch off into?
tracheoles
How does oxygen diffuse directly into the respiring cells?
the tracheae splits off into tracheoles which have thin permeable membranes which attach to individual cells
What does the insect use to move the air in and out?
Rhythmic abdominal movements
What do insects do if they are losing too much water through gas exchange?
Close their spiracles
Which features of an insect reduce evaporation?
Tiny hairs around spiracles
Waxy cuticle layer on their skin
What happens when a plant becomes dehydrated?
Guard cells close
They become flaccid which closes the pore to reduce evaporation
What are xerophytes?
Plants adapted to live in dry, warm or windy habitats
What features do xerophytes have to reduce water loss and how do they reduce it?
Sunken stomata - trap water vapour
Hairs on epidermis - trap water vapour
Curled leaves - protect from wind
Fewer stomata - less places for it to escape
Thicker waxy, waterproof cuticles - reduce evaporation
Explain how two features of the gills allow efficient gas exchange? (2 marks)
1) Large surface area = larger gas exchange surface
2) Thin = short diffusion pathway
Both increase the rate of diffusion
Suggest why the volume of water passing over the gills increases if the temperature of the water increases (1 mark)
The fish has a higher metabolism
How would you measure the surface area of a leaf? (3 marks)
1) place the leaf on a grid and draw around
2) count how many squares it takes up, including any that are more than half
3) multiply by two (both sides)
Explain why abdominal pumping increases the efficiency of gas exchange between the tracheoles and muscle tissue of an insect. (2 marks)
1) more air can enter more quickly
2) maintains concentration gradient
What is the advantage of insects opening its spiracles at a lower frequency in very dry conditions?
Lose less water vapour by evaporation
