exchanging substances Flashcards
what do organisms exchange substances with
their environment
multicellular organisms need
exchange surfaces
single called organisms have a
large surface area compared to their volume
multicellular organisms have
a smaller surface area compared to their volume
gas exchange occurs in the
lungs
lungs contain millions of little air sacs called
alveoli
how are alveoli specialised for diffusion of oxygen and carbon dioxide
large surface area
thin walls
good blood supply
explain how alveoli work
they diffuse carbon dioxide in from the blood and oxygen into the blood
where are villi located
small intestine
villi provide a
big surface area
why do villi need a big surface area
so digested food is absorbed more quickly into the blood
what do villi have
single layer of surface cells
good blood supply
