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AQA A Level Biology復習筆記3.1.1 Surface Area to Volume Ratio

Category: A-level課程, 教材筆記, 福利干貨 Date: 2022年6月27日下午12:03

Surface Area to Volume Ratio

Surface area?and?volume?are both very important factors in the?exchange of materials?in organisms
The surface area refers to the?total area of the organism that is exposed to the external environment
The volume refers to the?total internal volume of the organism?(total amount of space inside the organism)
As the surface area and volume of an organism increase (and therefore the overall ‘size’ of the organism increases), the surface area : volume ratio?decreases
This is because?volume increases much more rapidly than surface area as size increases

11.-Principles-of-surface-area-_-volume

As size increases, the surface area : volume ratio decreases

Maths Skill: Calculating SA:V Ratio

The surface area : volume ratio calculation differs for different shapes (these shapes can reflect different cells or organisms)

Calculating-SA_V-ratios

Worked Example

A researcher calculated the surface area of a large number of toad eggs. She calculated the mean surface area to be 10.12 mm². Toad eggs are generally?spherical. She calculated the surface area using the following equation:?4πr²Use this equation to calculate the mean?diameter?of a toad egg. Give your answer to?3.s.f.

?????? Step 1: Rearrange the equation to find the radius

r²?= surface area/4π

?????? Step 2:?Sub in relevant figuresr²?= 10.12 ÷ 12.56 = 0.805

?????? Step 3: Find the square root of r²Square root of 0.805 = 0.897

?????? Step 4:?Find the diameter from the radiusD = 2r

2(0.897) = 1.794

?????? Step 5:?Round to three significant figures

1.79 mm

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