Insects Gas Exchange

Question 1

Name the structures through which gases enter and leave the body of an insect

Answer 1

Spiracles

Question 2

Name the small tubes that carry gases directly to and from the cells of an insect.

Answer 2

Tracheoles

Question 3

Explain the movement of oxygen into the gas exchange system of an insect when it is at rest

Answer 3

1. Oxygen used in aerobic respiration
2. So oxygen concentration gradient is established
3. So oxygen diffuses

Question 4

Question and graph on abdominal pumping

Answer 4

1. Abdominal pumping/pressure in tubes linked to carbon dioxide release
2. Abdominal pumping raises pressure in body
3. Air is pushed out of the body and moves down the pressure gradient into the atmosphere.

Question 5

Explain how the presence of gills adapts the damselfly to its way of life

Answer 5

Damselfly larve has higher metabolic rate so uses more oxygen.

Question 6

Suggest two ways the student could improve the quality of the scientific drawing of the gill

Answer 6

1. Don’t shade in

2. All lines must join up together

Question 7

the rate of abdominal pumping movements increases between 3.0 and 3.5 minutes. suggest the advantage of this change to the locust

Answer 7

enables aerobic respiration

Question 8

Explanation of what caused the rise in the rate of abdominal pumping movements between 1.5 and 2.0 minutes:

Answer 8

the higher carbon dioxide (CO2) concentration or lack of oxygen

Question 9

Explanation for the fall in the rate of abdominal pumping movements between 2.0 and 3.0 minutes – include two points:

Answer 9

1. The co2 is toxic

2. There is a lack of oxygen do aerobic respiration

Question 10

Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange

Answer 10

1. Tracheoles have thin walls so short diffusion distance to cells;
2. Highly branched/large number of tracheoles so short diffusion distance to cells;
3. Highly branched/large number of tracheoles so large surface area (for gas exchange);

Question 11

How are insects adapted to reduce water loss?

Answer 11

1. Waterproof/waxy cuticle all over their body surfaces = reduce evaporation.
2. Small SA:V ratio = minimise area over which water is lost.
3. Spiracles = can close to reduce water loss.
4. Tiny hairs around spiracles = reduces evaporation

Question 12

What is the structure of the gas exchange system of an insect?

Answer 12

1. Internal network of tubes = tracheae
2. Tracheae are supported by strengthened rings to stop them from collapsing.
3. Tracheae divide into smaller tubes called tracheoles.
   Tracheoles extend throughout the body tissues of the insect = in this way air and the oxygen it contains is brought directly to the respiring tissues. They have thin permeable walls and go to individual cells.

Question 13

How does the gas exchange surface of an insect work?

Answer 13

1. Air diffuses into the tracheae through spiracles. Respiring cells use oxygen, so lowers oxygen so oxygen diffuses down the concentration gradient towards the ends of the tracheoles where respiring cells are.
2. CO2 produced by respiring cells move down concentration gradient along tracheoles, into tracheae, towards the spiracles to be released into the atmosphere.
3. Insects use rhythmic abdominal movements to move air in and out of spiracles - speeds up gas exchange.

Question 14

What feature does trachea have?

Answer 14

Have thin, permeable walls.

Question 15

Explain how a large surface area is retained in the structure of an insect’s gas exchange surface.

Answer 15

It has many small, branching tracheoles

Question 16

Describe the difference between the transport of oxygens to muscles in insects and fish

Answer 16

Blood is not involved in the transport of respiratory gases in insects, but it is in fish.