Gas Exchange in Insects

Question 1

Properties of gas exchange

Answer 1

• Large surface area
• Thin (one layer of epithelial cells) - provide short diffusion pathway across gas exchange surface

Question 2

What does the organism do for gases across exchange surface?

Answer 2

Maintain concentration gradient

Question 3

How does single-celled organisms utilise diffusion?

Answer 3

Absorb and release gases by diffusion through their outer surface

Question 4

Why does single-celled organisms not need gas exchange?

Answer 4

• Large surface area
• Short diffusion pathway
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Question 5

What are trachea?

Answer 5

Insects having microscopic air-filled pipes used for gas exchange

Question 6

What are spiracles?

Answer 6

Air moves into the trachea through the pores on surface

Question 7

How does oxygen travel in insects?

Answer 7

Down the concentration towards the cell

Question 8

How does oxygen diffuses directly into respiring cells?

Answer 8

Tracheae branch into smaller tracheoles which have thin, permeable walls and go to individual cells

Question 9

Why does insect’s circulatory system doesn’t transport CO2?

Answer 9

Carbon dioxide from the cells move down its own concentration gradient towards the spiracles to be released into the atmosphere

Question 10

How does insect move air in out and out of spiracles?

Answer 10

Use rhythmic abdominal movements to move air in and out of the spiracles

Question 11

What is the unfortunate consequence of exchanging gases?

Answer 11

Lose water

Question 12

How are insects specialised if they are losing too much water through exchanging gases?

Answer 12

• They close their spiracles using muscles
• Waterproof waxy cuticles all around body and tiny hairs around spiracles to reduce evaporation

Question 13

Name the process by which carbon dioxide is removed from a single-celled organism?

Answer 13

Diffusion across body surface

Question 14

Explain why there is a conflict in terrestrial insects between gas exchange and conserving water

Answer 14

Gas exchange requires a thin permeable surface with a large surface area

Conserving water requires a thick waterproof surface with a small area.

Question 15

Explain how the tracheal system limits the size of insects

Answer 15

Relies on diffusion to bring oxygen to the respiring tissue

If insects are large it would take long for oxygen to reach the tissues rapidly enough to supply their needs

Question 16

Describe and explain what happens to the concentration of oxygen in the trachea when the spiracles are closed

Answer 16

Falls steadily and remains at the same level

Question 17

Suggest an explanation for this change in the concentration of oxygen when the spiracles are closed

Answer 17

Cells use up oxygen during respiration and so it diffuses out of the trachea and into the cells

With the spiracles are closed , no oxygen can diffuse in from outside to replace it

All oxygen used up and level fall

Question 18

Suggest what causes the spiracles to be open

Answer 18

Increasing level of carbon dioxide

Question 18

Suggest an advantage of this spiracle movement to a terrestrial insect.

Answer 18

Helps to conserve water because spiracles are not open continuously

therefore water does not diffuse out continuously

Question 19

Fossil insects have been discovered that are larger than insects that occur on Earth today.

What does this suggest about the composition of the atmosphere at the time where fossil insects lived.

Answer 19

It contained more oxygen

Question 20

The insects lives in a dry conditions

Suggest an advantage of the pattern of spiracle movements

Answer 20

Spiracles will not be open all the time

Therefore less water loss

Question 21

Abdominal pumping increases the efficiency of gas exchange between tracheoles and muscle tissue of the insect

Explain why

Answer 21

Increases efficiency

increase rate of air moving into the trachea through the spiracles

maintain a greater diffusion gradient

Question 22

Abdominal pumping is an adaptation not found in many small insects. These small insects obtain sufficient oxygen by diffusion

Explain how their small size enables gas exchange to be efficient without the need of abdominal pumping

Answer 22

Small size offer a short diffusion pathway to obtain oxygen

Question 23

The insects open its spiracles at a lower frequency in very dry conditions

Suggest one advantage of this

Answer 23

No water loss

Question 24

The ends of the tracheoles connect directly with the insect muscle tissue and filled with water. When flying, water is absorbed into the muscle tissue. Removal of water from tracheoles increase the rate of diffusion of oxygen between the tracheoles and muscle tissue.

Suggest one reason why:

Answer 24

They have gases able to diffuse more oxygen at a faster rate

Question 25

How does oxygen diffuse through respiring cells?

Answer 25

Air enters through holes called spiracles

O2 diffuses down the concentration gradient along the trachea

02 diffuses into the cells

Question 26

Why is ventilation helpful for insects?

Answer 26

Help to maintain a high concentration gradient