3A Exchange and Transport Systems Flashcards
Organisms and their environment
all organisms need to exchange things with their environment
Effects of SA:V
affects how quickly substances are exchanged (high SA:V- faster)
Exchange in Single-Celled Organisms
substances diffuse directly in/ out of cells through cell-surface membrane
diffusion distance is short- faster rate of diffusion
high SA:V (oxygen takes part in reaction as soon as it diffuses into the cell)
Why can’t diffusion happen directly in multi-cellular organisms?
diffusion distance in too large - some cells are deep within body far from outer surface
large organisms - low SA:V therefore a slower rate of diffusion, exchange of sufficient substances hard
How are multi-cellular organisms adapted to exchange substances?
Have exchange organs (lungs)
Mass transport system (circulatory system)- efficient system to carry substances to cells
Body Size and Heat Loss
Large organisms (small sa:v) harder to lose heat Small organisms (high sa:v) lose heat quickly
Consequences of Small organisms and heat loss
due to high sa:v, lose heat quicker, have a higher metabolic rate to produce heat (have to eat lots to survive)
Body Shape and Heat Loss
Compact shape, decreases sa:v making it harder to lose heat
Not compact, increases sa:v making it easier to lose heat
animals body shape adapted to suit environment
Adaptations to aid exchange
large sa:v means easier to lose water evaporation- some desert mammals have kidney adaptations to produce less urine
small mammals in cold areas have to eat lots of high energy foods to aid metabolic rate
small mammals have thick layers of fur and hibernate in the cold
Gas Exchange Surface
boundary between the internal environment and external environment of an organism
2 common qualities of a Gas Exchange Surface to increase diffusion
large sa
thin, often 1 layer of epithelial cells (short diffusion pathway)
Gill structure
Gill
Gill Filament- increase sa:v for gas exchange
Gill Lamellae- increase sa further, have lots of capillaries with thin layer to increase diffusion
Counter-current Flow
blood and water flow in opposite directions through lamellae, ensures oxygen poor water always flows by oxygen rich blood, maintains a steep gradient of O2 exchange that is favourable through whole length
Gas Exchange in Plants
Mesophyll cells- maintain gas exchange surface in leaves (adapted to have high sa:v)
gases move in and out via stomata, guard cells open stomata ( let gases exchange) and close stomata ( stop water loss)
Gas exchange in insects
air flows down the trachea from the spiracles, oxygen travels down it’s concentration gradient into the tracheoles and diffuses directly into respiring cells
CO2 diffuses down it’s own conc gradient; exits out of the spiracle
abdominal movements move air in and out of the spiracles
