3.1 Surface area : volume ratio Flashcards
What does the surface area relate to (the demand or the supply of oxygen)
Relates to the supply of oxygen to the respiring cells
What does the volume relate to (the demand or the supply of oxygen)
Relates to the demand of the respiring cells
What does increasing the surface area to volume ratio do
It increases the supply of oxygen relative to the demand of oxygen - so smaller organisms benefit
What does a large SA:Vol ratio mean
That there is efficient exchange across their body surface
What increases faster in larger organisms (volume or surface area)
Volume increases faster than their surface area
What are the 5 properties of specialised systems from exchange
- Large surface area
- Very thin
- Permeable
- Maintain concentration gradient
- Moist ( allows gases to dissolve so diffuse easier)
Name 4 general things that need to be exchanged between organisms and their environment
- Respiratory gases
- Nutrients
- Excretory products
- Heat
Calculate the SA:Vol ratio of a cube that has sides 10mm long
6:10 = 0.6
Name 5 factors that affect the rate of diffusion of substances into cells
- Surface area
- Thickness of membrane
- Permeability of membrane
- Concentration gradient
- Temperature
Explain the advantage for larger animals of having a specialised system that facilitates oxygen uptake (2 marks)
- Larger organism have smaller SA: Vol
- Overcomes long diffusion pathway
Mammals such as a mouse and a horse are able to maintain a constant body temperature. Use your knowledge of SA:Vol to explain the higher metabolic rate of a mouse compared to a horse (the mouse has a higher one) (3 marks)
- Mouse has larger SA:Vol
- More/ faster heat loss
- Faster rate of respiration releases heat
Explain why oxygen uptake is a measure of metabolic rate in organisms (1 mark)
Oxygen is used in respiration, which provide energy/ ATP
OR
Oxygen is used in respiration, which is a metabolic process
