What mathematical relationship compares the surface area available for exchange with the internal volume of a cell or organism?
Surface area to volume ratio
Often written as SA:V ratio; determines how efficiently substances can move in or out.
As the size of a cell increases, how does the ratio of surface area to internal volume change?
Decreases
Volume increases faster than surface area as size increases.
Why do very small organisms rely mainly on diffusion across their body surface for exchange?
Large surface area to volume ratio
A high ratio allows sufficient exchange of substances directly across the surface.
Why is diffusion alone often insufficient for exchange in large multicellular organisms?
Small surface area to volume ratio
As organisms grow, their volume increases faster than surface area, limiting diffusion efficiency.
What general type of biological feature develops in larger organisms to help maintain efficient exchange with the environment?
Exchange systems
Examples include lungs, gills, and circulatory systems.
True or False:
As an organism grows larger, its volume increases at a faster rate than its surface area.
True
This mathematical relationship explains why SA:V decreases with increasing size.
True or False:
Large organisms usually rely entirely on diffusion across their body surface for gas exchange.
False
Most large organisms require specialised exchange surfaces and transport systems.
Fill in the blank:
As cells become larger, their ______ increases more rapidly than their surface area.
Volume
This leads to a reduced surface area to volume ratio.
How does a higher surface area to volume ratio affect the rate of diffusion into or out of a cell?
Increases diffusion rate
More surface is available relative to the internal volume requiring exchange.
What type of relationship exists between surface area to volume ratio and metabolic rate in organisms?
Positive relationship
Organisms with higher SA:V generally have higher metabolic rates.
True or False:
Cells with a higher surface area to volume ratio typically exchange substances more efficiently with their environment.
True
A greater relative surface area allows faster diffusion.
Fill in the blank:
In diffusion experiments, agar blocks containing indicator can be used to investigate how _______________________________ affects the rate at which a substance diffuses.
Surface area to volume ratio
Smaller agar cubes change colour more quickly due to higher SA:V.
What mathematical skill is required when comparing exchange efficiency in cells of different shapes or sizes?
Calculating surface area to volume ratios
Students may calculate SA and volume from given dimensions of cells.
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3.1.1 Monomers & Polymers9
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3.1.2 Carbohydrates22
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3.1.3 Lipids17
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3.1.4 Proteins39
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3.1.5 Nucleic Acids32
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3.1.6 ATP11
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3.1.7 Water11
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3.1.8 Inorganic ions8
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3.2.1 Cell structure52
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3.2.2 Cell division20
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3.2.3 Transport across cell membranes20
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3.2.4 Cell recognition & the immune system36
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3.3.1 Surface area to volume ratio13
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3.3.2 Gas exchange24
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3.3.3 Digestion & absorption16
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3.3.4 Mass transport39
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3.4.1 DNA, genes & chromosomes13
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3.4.2 DNA & protein synthesis14
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3.4.3 Genetic diversity & meiosis14
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3.4.4 Genetic diversity & adaptation20
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3.4.5 Species & taxonomy20
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3.4.6 Biodiversity within a community12
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3.4.7 Investigating diversity12
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3.5.1 Photosynthesis23
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3.5.2 Respiration17
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3.5.3 Energy & ecosystems20
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3.5.4 Nutrient cycles15
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3.6.1 Stimuli & Response62
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3.6.2 Nervous coordination53
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3.6.3 Skeletal muscles14
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3.6.4 Homeostasis57
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3.7.1 Inheritance12
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3.7.2 Populations15
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3.7.3 Evolution may lead to speciation22
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3.7.4 Populations in ecosystems24
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3.8.1 Gene Mutations and Protein Structure14
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3.8.2 Control of Gene Expression44
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3.8.3 Applications of Genome Projects10
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3.8.4 Gene Technologies and Their Applications46
