Exchange Surfaces Flashcards
What do organisms need to do to live?
needs to supply its cells with substances
it also needs to get rid of waste products
What can substances do?
diffuse (move) straight into and out of the cell across the cell membrane.
Why is diffusion fast?
substances only have to travel a short distance
single celled organisms have a large surface area to volume ratio so they can exchange enough substances across their cell membrane to supply the cell
Why is it more difficult to exchange substances in multicellullar organisms?
diffusion is too slow in the outer membrane
some cells are deep inside the organism - its a long way from them to the outside enviroment
larger organisms have a low surface area to volume ratio
What do multicellular organisms need?
specialised exchange surfaces
transport systems to carry marterials to the body cells and remove waste products
What is an example of specialised exchange surface?
alveoli
