Surface area and exchange Flashcards
Insects, fish and plant's gaseous exchange
Outline gas exchange in insects
They have a tracheal system which connects the air outside to the required tissues via the spiracles- tiny holes on the insect’s surface. The spiracles lead to tracheae which are held open by spiral cuticle bands. These branch to smaller tubes called tracheoles, and oxygen diffuses along the trachea and diffuses through the tracheoles’ cell membrane to the cells.
Why do the spiracles have valves?
So they can close & reduce water loss via evaporation
Why are the tracheoles thin?
To provide a short diffusion distance that allows the penetration of all body tissues.
How does CO2 then leave the body?
By the reverse pathway
What are the 3 ways respiratory gases move in and out of the tracheal system?
Down a diffusion gradient Mass transport (contracting muscles speed up gas exchange by squeezing the trachea The ends of the tracheoles are filled with water so there's a lower water potential from produced lactate and so water moves into cells from tracheoles by osmosis. The ends decrease in volume and air is drawn in.
Explain the surface area to volume ratios and give an example
As the size of the animal increases, the surface area decreases. Mice have a large SA to volume ratio and lose a large amount of heat relative to its mass. They respire at a high rate to help maintain temperature and have a high uptake of CO2.
Give 2 ways the gills are adapted
Large surface area due to large number if gill filaments which possess lamellae, which increase SA further.
Short diffusion pathway, blood and water are separated by a thin barrier of 2 cell layers: epithelial layer of lamellae and capillaries
Give 3 ways the gills are adapted?
It ensures continual blood flow and through the respiratory surface to absorb O2 and remove CO2.
Ventilation allows continual flow of water over gills, bringing more 02 and removing CO2.
The counter current system ensures that blood continually meets water with high {o2 ] so the diffusion gradient is maintained
Where does gas exchange occur in bony fish?
Over the surface area of the gills which has 4 pairs of gill arches containing many gill filaments protected by the operculum.
What are the main structures involved in plant gas exchange?
The stomata, mesophyll cells and air spaces between them
How are diffusion gradients maintained in plant gas exchange?
Respiration and photosynthesis maintain diffusion gradients by using and producing CO2 and O2.
How do gases diffuse into the plant?
Through the stomata down a concentration gradient and rapidly through air spaces. They diffuse across the thin cell wall and membrane of mesophyll cells.
How does the plant have a large surface area for gas exchange?
Numerous mesophyll cells lining the intercellular air spaces provide a large surface area.
Why does the stomata open during daylight and close at night?
To allow CO2 to enter for photosynthesis so transpiration can occur through the stomata. They close at night to limit transpiration and water loss.
