Surface area to volume ratio Flashcards – AQA A-Level Biology - (7402)

What is the surface area to volume ratio of an organism or structure?

Its surface area divided by its volume.

How do surface area and volume scale with linear dimension for similarly shaped structures?

Surface area scales with the square of the linear dimension; volume scales with its cube.

As similarly shaped structures increase in size, what happens to their surface area to volume ratio, and why?

It decreases because volume grows faster than surface area.

What does a smaller surface area to volume ratio mean for exchange?

Less surface is available for exchange per unit volume.

How does an organism’s external surface area relative to its volume change as it gets larger?

It becomes smaller.

Why may exchange across the body surface alone fail to meet a larger organism’s internal cells’ needs?

There is less surface area relative to volume, and substances must travel farther to reach internal cells.

How can a thin or flattened body shape help an organism exchange substances?

It increases surface area relative to volume and shortens diffusion distances.

What feature of specialised exchange surfaces helps larger organisms exchange substances?

They have a large surface area.

What is the role of transport systems in exchange in larger organisms?

They move substances between exchange surfaces and cells throughout the body.