6.1 exchange between organisms and their environment Flashcards
where does transfer of materials take place?
At exchange surfaces, and involves crossing cell plasma membranes.
What is tissue fluid?
the environment around cells of multi cellular organisms
What is a mass transport system?
A system whereby absorbed materials are distributed into tissue fluid and waste products are returned to the exchange surface for removal.
Why is a mass transport system necessary?
the majority of cells are too far from the exchange surface for diffusion alone to supply/remove materials and keep composition constant.
What is the role of a mass transport system?
to maintain diffusion gradients that bring materials to cell surface membranes.
what factors effect the amount of material exchanged?
size and metabolic rate.
What 4 things are exchanged between organisms and their environment?
respiratory gases, nutrients, excretory products, heat
aside from heat, what are the two ways in which materials are exchanged?
1) PASSIVELY- diffusion, osmosis.
2) ACTIVELY- active transport
Which organisms cannot survive by diffusion across the outer surface?
- organisms with a large surface area to volume ratio
- organisms with a large volume (substances can’t reach the middle)
- organisms which are very active.
how have organisms evolved for exchange?
- they have a flattened shape so no cell is far from the surface (leaf)
- exchange surfaces with large areas to increase the surface area to volume ration (lungs, gills)
What are the features of specialized exchange surfaces?
- large surface area relative to volume, increases rate of exchange
- very thin so diffusion distance is short
- selectively permeable
- movement of the environment (EG: air) to maintain a diffusion gradient
- internal movement to maintain diffusion gradient (EG: blood)
