Exchange Of Materials Flashcards
what do all organisms have to do relating to their environments
- they must take in substances that they need from the environment
- and get rid of any waste products
how can oxygen be an example of how organisms take substances from their environment and produce products to get rid of
- cells need oxygen for aerobic respiration which produces carbon dioxide as a waste product
- these two gases move between cells and the environment by diffusion
how can water be an example of how organisms take substances from their environment and produce products to get rid of
- water is taken up by cells by osmosis
- in animals, dissolved food molecules and minerals diffuse along with it
how can urea be an example of how organisms take substances from their environment and produce products to get rid of
- urea diffuses from cells to the blood plasma
- for removal from the body by the kidneys
what is dependent on the organisms surface area to volume ratio
how easy it is for an organism to exchange substances with its environment
what is urea
a waste product produced by animals from proteins
what does a ratio show
how big one value is compared to another
how does an organism becoming larger affect the surface area to volume ratio
the larger the organism, the smaller its surface area is compared to its volume
what would be the surface area to volume ratio ratio be of a mouse in a 1cm by 1cm block
- surface area is (1x1) x 6 = 6cm^2
- volume is 1x1 = 1cm^3
- suface area to volume ratio is 6:1
how do gases and dissolved substances enter single celled organisms
gases and dissolved substances can diffuse directly into the cell across the cell membrane
why can a single celled organism have gases and dissolved substances diffuse directly into it
- because they have a large surface area compared to their volume
- so enough substances can be exchanged across the membrane to supply the volume of the cell
what do multi cellular organisms have compared to single celled organisms
- a much smaller surface area compared to their volume
- or a much smaller surface area to volume ratio
what is the effect of multi cellular organisms having a smaller surface area to volume ratio
it makes it difficult to exchange enough substances to supply their entire volume across their outside surface alone
what do multi cellular organisms need if they have a small surface area to volume ratio
- some sort of exchange surface for efficient diffusion
- and a mass transport system to move substances between the exchange surface and the rest of the body
what must the needed exchange surfaces for a multi cellular organism be able to do what have done to be able to do this
- it must allow enough of the necessary substances to pass through
- so they are adapted to maximise effectiveness
