Exchange- Gas Exchange Flashcards
How is being thin beneficial in gas exchange surfaces?
This provides a short diffusion pathway across the gas exchange surface
What increases the rate of diffusion?
- Large surface area
- Thin
- Steep concentration gradient
How do single-celled organisms absorb and release gases?
By diffusion through their outer surface
Why don’t single-celled organisms need a gas exchange system?
They have a large surface area, a thin surface and a short diffusion pathway
Why do fish have special adaptations for gas exchange?
There’s a lower concentration gradient of oxygen in water than in air
How does oxygen get to the gills in fish?
Water enters the fish through the mouth and passes through the gills
What is the structure of the gills?
Made of lots of thin plates called gill filaments which are covered in tiny structures called lamellae
How is the surface area increased in gills?
Filament increase surface area and lamellae increase it more
How do gill lamellae speed up diffusion?
They have lots of blood capillaries and a thin surface area of cells
What is the counter-current system?
Blood flows through the lamellae in one direction and water flows over in the other direction
Why is counter-current flow important?
Maintains a large concentration gradient between the water and the blood
Where is concentration of oxygen higher?
In the water than in the blood so as much oxygen as possible diffuses from the water into the blood
What are tracheae?
Microscopic air-filled pipes that insects use for gas exchange
How does air move into the tracheae?
Through pores on the surface called spiracles
What way does oxygen travel in insects?
Down the concentration gradient towards the cells
What does the tracheae branch into?
Smaller tracheoles which have thin, permeable walls and go to individual cells which means that oxygen diffuses directly into the respiring cells as the insect’s circulatory system doesn’t transport oxygen
What way does carbon dioxide travel in insects?
Moves down its concentration gradient towards the spiracles to be released into the atmosphere
How do insects move air in and out of the spiracles?
By using rhythmic abdominal movements
Where do dicotyledonous plants exchange gases?
At the surface of the mesophyll cells
Why do plants need to exchange gases?
They need carbon dioxide for photosynthesis (produces oxygen as a waste product) and they need oxygen for respiration (produces carbon dioxide as a waste product)
How are mesophyll cells in the leaf well adapted?
Have a large surface area
How do gases move to the mesophyll cells (that are inside the leaf)?
Gases move in and out through pores in the epidermis called stomata
What do guard cells do?
Control the opening and closing of stomata
What can the stomata do to allow gas exchange and control water loss?
- Open to allow exchange of gases
- Close if plant is losing too much water
What is the conflict between gas exchange and water loss?
Features that make an efficient gas exchange system also increase water loss
How do insects minimise water loss?
Close their spiracles
How do insects reduce evaporation?
They have a waterproof, waxy cuticle all of the body and tiny hairs around their spiracles
When are plants’ stomata usually open?
During the day to allow gaseous exchange
What opens the stomatal pore?
Water enters the guard cells to make them turgid
What happens if the plant gets to dehydrated?
The guard cells lose water and become flaccid which closes the pore
What are xerophytes?
Plants that are specially adapted for life in warm, dry or windy habitats where water loss is a problem
How is sunken stomata in xerophytes a good adaptation?
Reduces the concentration gradient of water between the leaf and the air which reduces the amount of water diffusing out of the leaf and evaporating away
How is a layer of hairs on the epidermis in xerophytes a good adaptation?
Traps moist air round the stomata
How is curled leaves with the stomata inside in xerophytes a good adaptation?
Protects them from wind as windy conditions increase the rate of diffusion and evaporation
How is a reduced number of stomata in xerophytes a good adaptation?
So that there are fewer places for water to escape
How is waxy waterproof cuticles on leaves and stems in xerophytes a good adaptation?
Reduce evaporation
