surface area to volume ratio Flashcards

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1
Q

Describe the relationship between the size and structure of an organism and
its surface area to volume ratio (SA:V)

A

● As size increases, SA:V tends to decrease
● More thin / flat / folded / elongated structures increase
SA:V

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2
Q

How is SA:V calculated?

A

Divide surface area (size length x side width x number of sides) by volume (length x width x depth)

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3
Q

Suggest an advantage of calculating SA:mass for organisms instead of SA:V

A

Easier / quicker to find / more accurate because irregular shapes

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4
Q

What is metabolic rate? Suggest how it can be measured

A

● Metabolic rate = amount of energy used up by an organism within a given period of time
● Often measured by oxygen uptake → as used in aerobic respiration to make ATP for energy release

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5
Q

Explain the relationship between SA:V and metabolic rate

A

As SA:V increases (smaller organisms), metabolic rate increases because:
● Rate of heat loss per unit body mass increases
● So organisms need a higher rate of respiration
● To release enough heat to maintain a constant body temperature ie. replace lost heat

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6
Q

Explain the adaptations that facilitate exchange as SA:V reduces in larger
organisms

A
  1. Changes to body shape (eg. long / thin)
    ● Increases SA:V and overcomes (reduces) long diffusion distance / pathway
  2. Development of systems, such as a specialised surface / organ for gaseous exchange e.g. lungs:
    ● Increases (internal) SA:V and overcomes (reduces) long diffusion distance / pathway
    ● Maintain a concentration gradient for diffusion eg. by ventilation / good blood supply
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