Transport in Animals Flashcards

All 6 cards in this deck

Which substances must be transported into and out of organisms?

Oxygen, carbon dioxide, water, dissolved food molecules, mineral ions and urea.

How is the surface area : volume ratio of an object worked out?

Divide the surface area by the volume and write the answer as a ratio to 1: SA : V = surface area ÷ volume (e.g. 3 : 1).

True or false? As an organism gets larger, its surface area : volume ratio increases.

False. The ratio decreases — volume increases faster than surface area.

Why can a single-celled organism rely on diffusion across its body surface alone?

It has a large surface area : volume ratio and short diffusion distances, so diffusion is fast enough to meet its needs.

Why do multicellular organisms need a transport system as well as exchange surfaces?

They have a small surface area : volume ratio and long diffusion distances, so diffusion alone is too slow to supply their high metabolic demand.

In an experiment where agar cubes of different sizes are placed in dye, which cube has dye reach its centre first?

The smallest cube.
It has the largest surface area : volume ratio and the shortest diffusion distance to its centre.