7.4 Ventilation and gas exchange in other organisms Flashcards
Why do insects need gaseous exchange systems?
They have a tough exoskeleton through which little to no gaseous exchange can take place
Relatively high oxygen requirements
No blood pigments that carry oxygen
How has the gaseous exchange system of insects evolved?
To deliver oxygen directly to cells and remove CO2 the same way
What and where are spiracles?
Small openings along thorax + abdomen
What enters and leaves the spiracles?
Air
What only leaves the spiracles?
Water
In gas exchange, what do both mammals and insects need to be effective?
Maximised efficiency of gaseous exchange
Minimal loss of water
What structure controls the opening and closing of spiracles?
Sphincter
How do insects minimise water loss?
Keep spiracle sphincters closed as much as possible
When the insect is at rest, what state are the spiracles in? Why?
Closed - low O2 demand
When the insect is active, what state are the spiracles in? Why?
Open - High O2 demand and CO2 levels build up
What’s the first structure following the spiracles?
Trachea
Describe the structure of insect trachea.
- Largest tubes of insect respiratory system, 1mm in diameter
- Trachea run into and along the insect’s body
What is the function of insect trachea?
- Carry air into the body
What are the tubes of the insect trachea lined with?
Spirals of chitin
What is the function of spirals of chitin which line the tubes of the insect trachea?
Keep the tubes open when they’re bent or pressed
What are the characteristics of chitin?
Relatively impermeable to gases and so little gaseous exchange can occur in the trachea
What do the trachea branch into?
Tracheoles
Describe the structure of tracheoles.
- Tubes with a diameter of 0.6-0.8 μm
* Each tracheole is a single, elongated cell with no chitin lining
What does the lack of chitin lining in tracheoles mean?
Tracheoles are freely permeable to gases
What is the benefit of the small size of tracheoles?
Spread throughout the insect’s tissues and cells - this is where most gas exchange occurs between air and respiring cells.
Through what process does air usually move along the trachea and tracheoles?
Diffusion
How are tracheoles in insects an adaptation for gas exchange?
The tracheal have a large SA - this maximised gas exchange
How does oxygen enter the insect?
Oxygen dissolves in moisture on the tracheole walls and diffuses into surrounding cells
What is towards the end of the tracheoles? What’s the function of this
Tracheal fluid - limits penetration of air for diffusion
What happens when an insect is highly active, such as during flight, and the insect’s oxygen demands build up?
Lactic acid builds up in the insect’s tissues.
Due to this, water moves out of the tracheoles by osmosis.
What system supplies all of the insect’s oxygen demands?
Tracheal system
What controls the extent of gas exchange in insects?
Opening and closing of spiracles
What are the 2 alternative methods which large insects with high energy demands use, such as beetles, to increase the level of gas exchange?
- Mechanical ventilation
2. Collapsible trachea / air sacs
Describe the method of mechanical ventilation in large insects with high energy demands.
Air is actively pumped into the tracheal system by muscular pumping movements of the thorax
• These movements change the vol. of the body, whichc changes the pressure in the trachea + tracheoles
• Air is drawn into the trachea + tracheoles OR forced out as pressure changes
Describe the function of collapsible, enlarge trachea or air sacs.
Act as reservoirs - used to increase amount of air moved through gas exch. system
• The trachea / air sacs are inflated + deflated by ventilating movement of thorax + abdomen
