Topic 3 - Exchange + Mass Transport Flashcards
what is formula for diffusion?
diffusion ∝ (surface area x difference in concentration) / length of diffusion path
how do gases enter and leave the tracheae of an insect?
through spiracles on the body surface
how are spiracles opened and closed?
By a valve
what happens when the spiracles are opened?
water vapour can evaporate from the insect
what are the limitations of the tracheal system?
relies mostly on diffusion for diffusion to be effective, the diffusion pathway needs to be short, which is why insects are of a small size so the length of the diffusion pathway limits the size that insects can attain
How does gas exchange in insects work?
Air enters via spiracles, travels through trachea and tracheoles, delivering
oxygen directly to every tissue.
what is the outside of a fish like?
waterproof → gas-tight
what is the structure of the gills?
- made up of gill filaments
- they’re stacked up in a pile
- gill lamellae are at right angles to the filaments
- increases surface area
how is water passed through in fish?
- water is taken through the mouth and forced over the gills and out through an opening on each side of the body
- flow of water over the gill lamellae is opposite to the direction of the flow of blood
what does the countercurrent flow mean for gas exchange?
- Blood that is already well loaded with oxygen meets water, which has its maximum concentration of oxygen. Therefore diffusion of oxygen from the water to the blood takes place.
- Blood with little oxygen in it meets water which has had most of its oxygen removed. diffusion or oxygen from the water to blood takes place.
- as a result a diffusion gradient for oxygen uptake is maintained across the entire width of the gill lamellae
what are the adaptations for rapid diffusion in leaves?
- many stomata, no cell is far from a stoma and therefore the diffusion pathway is short
- numerous interconnecting air-spaces that occur throughout the mesophyll so that gases can readily come in contact with mesophyll cells
- large surface area of mesophyll cells for rapid diffusion.
how have insects adapted to reduce water loss?
- Small surface area to volume ratio
- to minimise the area over which water is lost.
- Waterproof coverings over their body surfaces.
- in the case of insects this covering is a rigid outer skeleton of chitin that is covered with a waterproof cuticle.
- Spiracles
- the openings of the tracheae at the body surface and these can be closed to reduce water loss
- tracheae
- carry air containing oxygen directly to the tissues
How do plants reduce water loss?
waterproof covering over parts of the leaves and the ability to close stomata when necessary
what are xerophytes?
plants that are adapted to living in areas where water is in short supply
what are examples of adaptations in xerophytes?
a reduced surface area to volume ratio of the leaves
stomata in pits or grooves
hairy leaves
rolling up of leaves
a thick cuticle