Exchange Between Organisms And The Environment

Question 1

What does transfer of materials always involve?

Answer 1

It always involves the crossing of cell plasma membranes.

Question 2

What is the environment around multicellular organisms known as?

Answer 2

Tissue fluid.

Question 3

What brings materials to and from the cell-surface membrane?

Answer 3

Mass transport systems.

Question 4

What are the two factors that affect the amount of material that is exchanged?

Answer 4

The size and metabolic rate of an organism.

Question 5

What transfers more material: organisms with a high or low metabolic rate?

Answer 5

Organisms with a high metabolic rate.

Question 6

What do organisms with a high metabolic rate require?

Answer 6

A large surface area to volume ratio.

Question 7

What needs to be exchanged between an organism and its environment?

Answer 7

Respiratory gases
Nutrients
Excretory products
Heat

Question 8

What respiratory gases are required by organisms?

Answer 8

Oxygen

Carbon dioxide

Question 9

What nutrients are required by organisms?

Answer 9

Glucose
Fatty acids
Vitamins
Minerals

Question 10

What are the two excretory products removed from cells?

Answer 10

Carbon dioxide

Urea

Question 11

What are the two ways in which materials are interchanged?

Answer 11

Passively

Actively

Question 12

What is meant by passive exchange?

Answer 12

No metabolic energy is required.

Question 13

What is meant by active exchange?

Answer 13

Metabolic energy is required.

Question 14

What are the two passive methods of exchange?

Answer 14

Diffusion

Osmosis

Question 15

What is the method of active exchange?

Answer 15

Active transport

Question 16

What is necessary to ensure effective gas exchange?

Answer 16

A large surface area compared to their volume.

Question 17

What happens as an organism becomes larger?

Answer 17

Their volume increases at a faster rate than their surface area so the SA:V is lower.

Question 18

What type of SA:V does a small organism have?

Answer 18

They have a large SA:V

Question 19

What is a large SA:V good for?

Answer 19

Simple diffusion

Question 20

Why is simple diffusion sufficient for small, inactive organisms?

Answer 20

They have a large SA:V so diffusion is efficient and they also do not require much energy as they are inactive.

Question 21

What features have organisms evolved to aid gas exchange?

Answer 21

A flattened shape.

Specialised exchange surfaces with large surfaces areas.

Question 22

Why do some exchange surface surfaces have a flattened shape?

Answer 22

This is so no cell is ever far from the surface.

Question 23

Why do specialised exchange systems have large areas?

Answer 23

To increase the SA:V.

Question 24

How do you calculate the SAV.?

Answer 24

4🍰r^2 for SA

4/3🍰r^3

Question 25

What are the 5 features of specialised gas exchange systems?

Answer 25

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 to cross.
Movement of the environmental medium, for example, air, to maintain a diffusion gradient.
A transport system to ensure the movement of the internal medium, for example, blood, in order to maintain a diffusion gradient.

Question 26

What is diffusion directly proportional to?

Answer 26

Diffusion ➰ (surface area X difference in concentration)/ length of diffusion.

Question 27

What are two problems with exchange surfaces being thin?

Answer 27

They are easily damaged and dehydrated.

Question 28

Why are exchange surfaces located inside an organism?

Answer 28

This is because they’re easily damaged and dehydrated so it is better to locate the exchange surface inside the organism.

Question 29

If the exchange surface is located inside the body what is needed?

Answer 29

A means of moving the external medium over the surface is needed.