CGP Gas Exchange Flashcards
3 examples of when organisms need to exchange substances with their environment?
- oxygen for aerobic respiration
- excrete waste products eg urea and carbon dioxide
- heat (in order to remain at same temperature)
What kind of SA:V ratio do small animals have?
Large SA:V ratio.
Unlike single called organisms, why is diffusion across the outer membrane in multicellular organisms too slow?
- some cells are deep within the body; a big distance between them and the outside environment.
- larger animals have a small SA:V ratio; difficult to exchange substances for a large volume of animal from a small SA.
Most gas exchange systems have two things in common…
- large SA
- they’re thin (just one layer of epithelial cells); providing a short diffusion pathway across gas exchange pathway
What system do fish use for gas exchange?
Counter current system
Why do fish need to use a counter current system?
Because there’s a lower concentration of oxygen in water than in air.
Outline how the counter current system works in fish.
- Water enters the mouth, then through the gills (each of which is made of gill filaments, providing a large SA for gas exchange).
- The gill filaments also have lamellae, further increasing SA.
- Blood flows through the lamellae in one direction and water flows in the opposite direction. This maintains a large conc. gradient between the water and blood.
What do insects use for gas exchange?
Tracheae
What adaptations do the lamellae in fish have for gas exchange?
They increase the SA (as they are tiny structures on full filaments).
They also have lots of blood capillaries and a thin surface layer of cells to speed up the rate of diffusion.
Outline gas exchange in the tracheae in insects.
- Air moves into the tracheae through spiracles (pores on the surface).
- Oxygen travels down the conc. gradient towards the cells.
- Tracheae break down into smaller tracheoles and go into individual cells. This means oxygen diffuses directly into respiring cells
- CO2 from the cells moves down its own conc. gradient towards the spiracles to be released into the atmosphere.
What are tracheae?
Microscopic air filled pipes used by insects for gas exchange.
Where do dicotyledonous plants do gas exchange?
At the surface of mesophyll cells.
How are mesophyll cells adapted to their function of gas exchange?
They have a large SA.
In mesophyll cells, gases move in and out of…
Pores in the epidermis called stomata.
Stomata open to…
Allow the exchange of gases.
Stomata close to…
Prevent the plant from losing too much water.
What do guard cells do?
Control the opening and closing of stomata.
Gas exchange causes water loss. But how do insects avoid losing too much water?
If insects are losing too much water, they close their spiracles using muscles.
They also have a waterproof, waxy cuticle all over their body and tiny hairs, both of which reduce evaporation.
Gas exchange causes water loss. But how do plants prevent too much water loss?
Plant’s stomata are kept open during the day to allow gas exchange. Water enters guard cells, making them turgid and opening the stomatal pore. If the plant starts to get dehydrated, the guard cells lose water and become flaccid, which closes the pore.
What are xerophytes?
Plants that are specially adapted for warm, dry or windy habitats where water is a problem.
Give examples of some xerophytic adaptations.
- reduced number of stomata to reduce water loss
- a layer of hairs on epidermis, to trap moist air round the stomata
- waxy, waterproof cuticles on leaves and stem to reduce evaporation
- curled leaves with stomata inside, protecting them from wind (as windy conditions increase the rate of diffusion and evaporation)
As you breathe in, air enters the _________.
Trachea (windpipe).
The trachea splits into 2 _________.
Bronchi.
One broncos then leads to each lung.
Each broncus then branches off into smaller tubes aka _____________.
Bronchioles.
