13.1 Exchange between organisms and their environment

Question 1

Why do organisms require a transport system?

Answer 1

Because organisms must transfer materials between themselves and their environment. Materials need to be rapidly distributed to the cells that need them, and waste products to the exchange surface for removal.

Question 2

Four examples of things that need to be exchanged between an organism and the environment?

Answer 2

• Heat
• Respiratory gases (oxygen and co2)
• Nutrients (glucose, fatty acids, amino acids, vitamins, minerals)
• excretory products (urea and co2).

Question 3

Exchange can take place in two ways.

Answer 3

Passively (no energy) (diffusion and osmosis)

Actively (energy) (active transport).

Question 4

How can exchange be effecive?

Answer 4

If the surface area is large compared to volume.

Question 5

Two ways which organisms have evolved to allow efficient exchange?

Answer 5

• A flattened shape = no cell is far from surface

- Specialised exchange surfaces with large areas to increase surface area to volume ratio.

Question 6

Exchange surfaces have what five features?

Answer 6

• Large SURFACE AREA to volume ratio.
• Very thin (shorter diffusion pathway).
• Partially permeable
• Movement of environmental medium to maintain a diffusion gradient.
• Movement of internal medium to maintain a diffusion gradient.