Exchange systems (DWR) Flashcards
Which organism would have a larger surface area to volume ratio and why: Mouse or an elephant?
Mouse because it’s smaller
How do single celled organisms exchange gases?
Simple diffusion through their outer membrane
How are flatworms and leaves adapted for efficient gas exchange?
They are flat so no cell is ever far from the surface and diffusion distances are shorter
Specialised gas exchange systems in mammals
Lungs/respiratory system
Specialised gas exchange systems in fish
Gills
Specialised gas exchange systems in insects
Tracheal system
Why do smaller mammals have a faster rate of respiration than larger ones?
They lose more heat so need more oxygen to generate energy to maintain a constant body temperature
What 3 things does the efficiency of a gas exchange system depend on?
Surface area
Diffusion distance
Concentration gradient
Name the process by which carbon dioxide is removed form a single celled organism
Simple diffusion
Explain why there is a conflict in insects between gas exchange and conserving water
Gas exchange requires a thin permeable surface with a large area but conserving water requires a thick waterproof surface with a small area
Why does the tracheal system limit the size of insects?
It relies on diffusion to bring oxygen to respiring tissue but if insects were bigger then it would take too long for oxygen to reach respiring tissue
What are the openings in which gas enters and leaves an insect called?
Spiracles
What are the network of tubes in an insect for gas exchange called?
Tracheae
What are the tubes that trachea divide into called?
Tracheoles
How is a concentration gradient for oxygen maintained in an insect?
Oxygen is used up by cells, maintaining a low concentration in the insects and a higher concentration in the atmosphere
How is a concentration gradient for carbon dioxide maintained in an insect?
Carbon dioxide in produced in respiration, so there is a higher concentration in the insect and it diffuses out
What is abdominal pumping and how does help maximise gas exchange?
Insects contract muscles, squeezing the trachea and enabling mass movements of air in and out
How does the tracheoles being filled with water benefit insects?
- Lactic acid produced in anaerobic respiration lowers water potential of muscle cells.
- Water in the tracheoles moves into muscle cells by osmosis.
- Less water in the tracheoles so air is drawn further in a diffusion is more rapid as its in a gas phase
- However it leads to greater water evaporation
Why do insects keep their spiracles closed most of the time?
To prevent water loss
What triggers insects to open their spiracles?
Increased CO2 concentration
Two limitations of tracheal system
- Insects must be small for a short enough diffusion pathway to their body cells
- Conflict between opening spiracles for gas exchange and water retention
What structures are gills made up of?
Gill plates, gill filaments, lamellae
Which structures maximise the surface area of a gill?
Lamellae
What is countercurrent flow?
The flow of blood and water in opposite directions over the lamellae