6.1: Exchange with the environment

Question 1

Examples of things that need to be interchanged between organism and its environment

Answer 1

• Respiratory gases (oxyygen and carbon dioxide)
• Nutrients (Glucose, fatty acids, amino acids, vitamins minerals)
• Excretory products (Urea and carbon dioxide)

Question 2

Processes by which exchange occur

Answer 2

Passively - Diffusion, osmosis, facilitated diffusion

Actively - Active transport

Question 3

Surface Area to Volume ratio

Answer 3

Small organisms have a surface area that is large enough, compared with their volume, to allow efficient exchange across their body surface

As organisms become larger, their volume increases at a faster rate than their surface area.

Larger organisms have developed specialised exchange surfaces

Question 4

Example of specialised exchange surfaces

Answer 4

• Flattened shape so that no cell is ever far from the surface e.g leaf
• Specialised exchange surfaces with large areas to increase the surface area to volume ratio e.g lungs in mammals, gills in fish

Question 5

Features of specialised exchange surfaces

Answer 5

• A large surface area relative to the volume of the organism which increases the rate of exchange
• Very thin so that the diffusion distance is short and therefore materials cross the exchange surface rapidly
• Selectively permeable to allow selected materials across
• Movement of the enviornmental medium, for example, air, to maintain a diffusion gradient

Question 6

Ficks Law

Answer 6

Question 7

Factors that affect the rate of diffusion

Answer 7

Surface area

Difference in concentration

Length of diffsion path/thickness of diffusion path