B1 Exchange Surfaces

How do you calculate a surface area to volume ratio (SA: V)

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What is an exchange surface?

• A specialised area of an organism that efficiently transfers substances between the organism and its environment.
• A specialised area of an organism that efficiently transfers substances between the organism and itself.

Why don't single-celled organisms need exchange surfaces?

• They have a large surface area to volume ratio meaning substances can easily diffuse into their cells.
• They have a small surface area to volume ratio meaning substances can sometimes diffuse into their cells.

Why do multi-cellular organisms need exchange surfaces?

• They have a small surface area to volume ratio. They need an exchange surface such as lungs to transfer substances efficiently.
• They have a large surface area to volume ratio. They do not need an exchange surface such as lungs to transfer substances efficiently.

Give FOUR adaptations of exchange surfaces that increase their effectiveness.

• Large surface area.
• Thin membrane
• Rich blood supply (in animals)
• Gas exchange surfaces are exposed to the air (in animals)
• Small surface area to volume ratio

Give THREE ways that the small intestine is adapted for exchanging surfaces

• Walls are folded and have millions of projections called villi to give a huge surface area.
• Villi have very thin walls.
• Villi have a rich blood supply.
• Villi have thick membranes

Give THREE ways that alveoli are adapted for gas exchange.

• Thin walls
• A rich blood supply
• Large surface area.
• Folded into spiral shapes

Give TWO ways that plant leaves are adapted for gas exchange.

• Openings in epidermal tissue called stomata let gases in and out of the leaf.
• Air spaces inside leaf tissues allow gases to diffuse in and out of cells.
• Transpiration lets oxygen escapre through these stomata

How does the structure of a fish's gills help it to exchange gases with water?

• Gills are made up of lots of gill filaments which are covered many folds called lamella. This provides a large surface area which increases the rate of difusion of gases between the fishe's blood and water.
• Gills are made up of lots of gill filaments which are covered many folds called lamella. This provides a small surface area which increases the rate of difusion of gases between the fishe's blood and water.

Give THREE ways that the lamellae in a fish's gills are adapted for exchanging gases with water.

• Thin walls
• A rich blood supply.
• Blood flows through them in opposite direction to water flowing over them.
• Finger-like projections called villi.