Why can an insect not exchange gases across its body surface?

The cuticle is thick, hard and waterproofed with wax, which prevents the insect drying out on land but also makes the surface impermeable to gases.

A spiracle is a pore in the body wall of an insect through which air enters and leaves the tracheal system.

How are the spiracles arranged on an insect?

They are arranged in pairs along the sides of the thorax and abdomen, typically two pairs on the thorax and up to eight on the abdomen.

What is a trachea in an insect, and how is it held open?

A trachea is an air-filled tube leading inwards from a spiracle, and it is lined with chitin thickened into spiral bands that keep it open as the body moves.

Tracheoles are the finest branches of the tracheal system, less than a micrometre across and without a chitin lining, and they end blindly among the cells of the tissues.

Why is it an advantage that the tracheoles run right in among the cells?

Oxygen is delivered as a gas to within a fraction of a micrometre of each cell, so the diffusion distance is minute and no transport in the blood is required.

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Adaptations for Gas Exchange

The insect tracheal system

3 things to know
Component 3

Overview

Trachea in an insect, tracheal fluid and air sacs.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

How does an insect limit the water it loses through the tracheal system?

Key term

Explain the conflict an insect faces between gas exchange and water conservation.

Key term

What is a spiracle?

Questions from this subtopic

Each one with the model answer underneath.

1
Why can an insect not exchange gases across its body surface?
Model answer
The cuticle is thick, hard and waterproofed with wax, which prevents the insect drying out on land but also makes the surface impermeable to gases.
2
What is a spiracle?
Model answer
A spiracle is a pore in the body wall of an insect through which air enters and leaves the tracheal system.
3
How are the spiracles arranged on an insect?
Model answer
They are arranged in pairs along the sides of the thorax and abdomen, typically two pairs on the thorax and up to eight on the abdomen.
4
What is a trachea in an insect, and how is it held open?
Model answer
A trachea is an air-filled tube leading inwards from a spiracle, and it is lined with chitin thickened into spiral bands that keep it open as the body moves.
5
What are tracheoles?
Model answer
Tracheoles are the finest branches of the tracheal system, less than a micrometre across and without a chitin lining, and they end blindly among the cells of the tissues.
6
Why is it an advantage that the tracheoles run right in among the cells?
Model answer
Oxygen is delivered as a gas to within a fraction of a micrometre of each cell, so the diffusion distance is minute and no transport in the blood is required.

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The insect tracheal system

Overview

What you need to know

How does an insect limit the water it loses through the tracheal system?

Explain the conflict an insect faces between gas exchange and water conservation.

What is a spiracle?

Questions from this subtopic

Why can an insect not exchange gases across its body surface?

What is a spiracle?

How are the spiracles arranged on an insect?

What is a trachea in an insect, and how is it held open?

What are tracheoles?

Why is it an advantage that the tracheoles run right in among the cells?

Other ways to work this

What is inside Levo

The 3-step method, run for you

Cram a whole paper in one sitting

Blank Blitz makes facts automatic

Build It gets the exam shape right

Test It catches misconceptions

Brain Breaks between sessions

Every question in Adaptations for Gas Exchange, on a schedule.