Gas Exchange

Question 1

Describe and explain the common adaptations of the gas exchange surfaces found in fish
and mammals. [3]

Answer 1

Highly folded + to increase surface area ( 1 mark )
Thin + to reduce diffusion distance / short diffusion pathway ( 1 mark )
Rich blood supply/extensive blood capillary network + to maintain diffusion/concentration gradient ( 1 mark )
Moist + gases to dissolve (1 mark)

Question 2

Suggest why warm-blooded animals which have a constant body temperature, e.g. mammals, have a higher metabolic rate. [2]

Answer 2

Energy is needed to generate heat ( to maintain body temperature)
Provides optimum temperature for enzymes ( so reaction rate higher)

Question 3

Suggest a role of the air sacs. [1]

Answer 3

To provide a resorvior of Oxygen when Spiracles are closed

OR aid in ventilation of the tracheal system

Question 4

Explain the advantage to the insect of having a ventilation system. [1]

Answer 4

To maintain a steep concentration gradient

Question 5

The chitin in the walls of the tracheae has a similar chemical bonding and function as cellulose in plant cell walls.
Explain how the chemical bonding in chitin enables
it to carry out this function in insects.

Answer 5

Beta-glucose form glycosidic bonds (1 mark)
{bonding / cross-linking} between {molecules/chains} / formation of microfibrils(1) Ignore hydrogen
{provides strength / is tough/ prevents collapsing} (of tracheae)(1)

Question 6

Identify organelles X in the diagram on page 5 and explain why they are found close
to the tracheoles
Mitochondria= Organelle X

Answer 6

Formation of ATP synthesis / aerobic respiration (1)

Tracheole is the site of gas exchange (1)