Surface Area:Volume Ratio & Gas Exchange Flashcards
what is gas exchange like in single-celled organisms?
they rely on diffusion for the exchange of oxygen and carbon dioxide down their concentration gradient
large surface area:volume ratio
why do large multicellular organisms need specialised exchange surfaces/transport systems?
they have a small surface:area ratio so they have to transport substances such as oxygen around the body
what adaptations has the body made for more efficient gas exchange?
(6 points)
lots of alveoli - larger surface area:volume ratio
alveolar epithelium is 1 cell thick - short diffusion distance
alveolar walls are elastic - stretches during inspiration and recoils during expiration which maintains the concentration gradient
lots of capillaries - maintains a large concentration gradient
ventilation - maintains the concentration gradient by expiring carbon dioxide and inspiring oxygen
capillary endothelium is 1 cell thick - short diffusion distance
what is gas exchange like in insects?
occurs via the tracheal system which can transport oxygen directly into respiring cells
ventilation creates a mass movement of air in and out of the tracheae from outside the insect via the spiracles
what is gas exchange like in fish?
counter-current flow system - blood flows in one direction and water flows in the other direction maintaining the concentration gradient along the whole length of the lamellae
what is gas exchange like in plants?
stomata on the lower epidermis of the leaves open and close allowing carbon dioxide to enter and oxygen to leave the plant
what is gas exchange like in humans?
oxygen is inspired which diffuses into the blood from the alveoli and carbon dioxide diffuses into the alveoli from the capillaries to be expired
how do insects limit water loss?
(3 points)
waterproof covering
small surface area:volume ratio
spiracles which open and close
how have xerophytic plants adapted to hot, dry conditions?
reduced number of stomata
hairs to trap water
rolled leaves
spines instead of leaves
thick waxy cuticle - limit water loss