Exchange surfaces

Question 1

Surface area:Volume

Answer 1

single celled-substances diffused directly (large sa to volume ratio)
Multicellular-need exchange surfaces(small surface area to volume ratio)
Thin membrane: short distance to diffuse through
Large SA: More substance can diffuse at once
Animals: Well ventilated/lots of blood vessels-air and blood to move in and out

Question 2

Organs

Answer 2

Lungs: alveoli- Thin walls,large SA,moist,good blood supply
Small intestine: villi- digest food quickly, single layer of surface cells, good supply of blood for quick absorption

Question 3

Plants

Answer 3

CO2 diffuses into air spaces
Stomata: underneath leaf, carbon dioxide enters through diffusion-oxygen and water vapour exit, flat shape increases surfaces area
Cell wall:Air spaces increase surface area-more CO2

Question 4

Fish

Answer 4

Gills: water (mouth to gills)Diffusion-oxygen(water to blood)CO2(blood to water)
Gill filaments: provide large surface area for gas exchange, contains lamellae(lots of blood capillaries-speed up diffusion)
Thin surface layer- minimise distancegas diffuses through