Gas exchange in single-celled organisms and insects

HideShow resource information
  • Created by: Alice
  • Created on: 28-05-14 11:43
Single-celled organisms are very small. Why is diffusion useful?
Very large SA: VOL ratio. Means that gas exchange only happens by diffusion across body surface as it is only covered by cell surface membrane. Oxygen and Carbon Dioxide exchanged this way.
1 of 9
Insects are terrestial - how is this a problem?
Live on land. Water easily evaporates from body surface, become dehydrated. Need to conserve water.
2 of 9
How is conserving water difficult with the need for efficient gas exchange?
Efficient gas exchange requires thin, permeable surface with large SA - conflicts with need to conserve water.
3 of 9
What are two ways whereby insects reduce water loss?
Waterproof coverings over body - rigid outer skeletons covered by waxy cuticles. Small SA to VOL to minimise area over which water is lost
4 of 9
Because insects can't use their body surface to diffuse respiratory gases like single-celled organisms, what do they do?
Develop internal network of tubes called tracheae, supported by strengthened rings to stop collapsing.
5 of 9
The trachea divide into smaller tubes called tracheoles - what do they do?
Tracheoles extend through body tissues of an insect to bring air directly to respiring tissues.
6 of 9
There are two ways that respiratory gases move in and out of tracheal systems. What are they?
Diffusion gradient - low O2 conc at respiring tissues, higher conc outside insect, gas moves down concentration gradient into insect. Opposite for CO2. Ventilation - muscle movements in insects create mass movements of air in/out of tracheae.
7 of 9
What is the function of the spiracles?
Gases enter/exit tracheae through spiracles/pores on body surface, controlled by valve.
8 of 9
Why are valves necessary in the control of an insect's gas exchange?
Allows the closing of spiracles to prevent water loss. Allow gas exchange when open.
9 of 9

Other cards in this set

Card 2

Front

Insects are terrestial - how is this a problem?

Back

Live on land. Water easily evaporates from body surface, become dehydrated. Need to conserve water.

Card 3

Front

How is conserving water difficult with the need for efficient gas exchange?

Back

Preview of the front of card 3

Card 4

Front

What are two ways whereby insects reduce water loss?

Back

Preview of the front of card 4

Card 5

Front

Because insects can't use their body surface to diffuse respiratory gases like single-celled organisms, what do they do?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Human, animal and plant behaviour resources »