2.2 adaptations for gas exchange Flashcards
what are the 4 attributes of a respiratory surface?
thin (short diffusion pathway), permeable to gases, moist, large surface area.
how does an organism’s size relate to its surface area to volume ratio?
the larger the organism, the lower the surface area to volume ratio.
how does surface area to volume ratio affect the transport of molecules?
the lower the surface area to volume ratio, the further the distance molecules must travel to reach all parts of the organism.
how do fish ventilate?
water is forced over the gill filaments.
what is an advantage of the gill filaments?
they increase the surface area of the gills.
describe the mechanism fish use to take in water.
the mouth opens and the operculum closes. the floor of the buccal cavity is lowered. volume of buccal cavity increases and pressure of buccal cavity decreases. water flows in as the external pressure is higher than that of the buccal cavity.
describe the mechanism fish use to force water out over the gills.
the mouth opens and the operculum closes. the floor of the buccal cavity is raised. the volume of the buccal cavity decreases and the pressure of the buccal cavity increases. water flows out as the pressure of the buccal cavity is higher than that in the opercular cavity and outside.
what is counter-current flow?
the blood in the gill capillaries flows in the opposite direction to the water flowing over the lamellae.
how does counter-current flow increase the efficiency of diffusion?
it maintains a steep concentration gradient across the whole gill filament as blood always hits water with relatively high oxygen content.
what is parallel flow?
water and blood flow in the same direction across the lamellae.
why is parallel flow inefficient?
it does not maintain a steep concentration gradient across the whole gill filament as equilibrium is reached between the water and the blood.
