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
What is the efficiency of the countercurrent flow system and why is it more efficient than parallel flow?
- It is 80% efficient
- Water always passes blood with a higher concentration of oxygen
- It maintains a concentration gradient across the whole length of the gill
- Parallel flow does not and it is only 50% efficient
What differences are there between the gills of more active and less active fish?
More active fish will have more gills filaments/lamellae for more gas exchange as they need more energy from respiration
Why do plants need gas exchange if they can reuse products of photosynthesis and respiration?
Photosynthesis doesn’t occur all the time, but respiration does so plants use oxygen from the air when not photosynthesising
Adaptations of leaves of dicotyledonous plants for rapid diffusion
- Air spaces with a large SA within the leaf so gases can diffuse in quickly ad get to mesophyll
- Large SA of mesophyll for rapid diffusion
- Many stomata for short diffusion pathway
Where are stomata found and why does this benefit the plant?
On the lower epidermis, it reduces the amount of water lost by evaporation as less sun hits the bottom of the leaf
What are the pair of cells that surround stomata called?
Guard cells
Are guard cells turgid or flaccid in the dark and why?
Flaccid, to close the stomata and conserve water
Are guard cells turgid or flaccid in the day and why?
Turgid, to open stomata and allow sunlight in
Adaptations in insects that limit water loss
- Small SA:V minimises area over which water is lost
- Waterproof covering over body surface
- Spiracles close when at rest to reduce water loss
Plant adaptations to reduce water loss
- Waterproof waxy cuticle
- Guard cells can close stomata
What is a xerophyte?
Plants adapted to living in areas with a limited water supply
Xerophyte adaptations to reduce water loss
- Thicker waxy cuticle
- Rolled up leaves. Creates a region saturated with water so there is no water potential gradient and water is not lost
- Hairy leaves. Traps still moist air and reduces water potential gradient
- Reduced SA:V of leaves
What organ is the site of human gas exchange?
Lungs
Name the 5 main parts of the human gas exchange system
- Lungs
- Trachea
- Bronchi
- Bronchioles
- Alveoli
What is the site of human gas exchange?
Alveolar membrane
What is ventilation? (lungs)
The process of air being moved in and out of the lungs
What is inspiration?
When atmospheric pressure is greater than pulmonary pressure and air is forced into the lungs (inhalation)
What is expiration?
When pulmonary pressure is greater than atmospheric pressure and air is forced out (exhalation)
Which 3 muscles bring about changes in pulmonary pressure?
Diaphragm
Internal intercostal muscles
External intercostal muscles
Contraction of internal intercostal muscle brings about…
Expiration
Contraction of external intercostal muscles brings about…
Inspiration
Process of inspiration (5)
- External intercostal muscles contract whilst internal intercostal muscles relax
- Ribs are pulled upwards and outwards causing an increase in thorax volume
- Diaphragm contraction further increases thorax volume
- increase in thorax volume decreases pressure in the lungs
- Atmospheric pressure is greater than pulmonary pressure and air forced into the lungs
Process of expiration (5)
- Internal intercostal muscles contract whilst external intercostal muscles relax
- Ribs are pulled downwards and inwards reducing thorax volume
- Diaphragm relaxes, further decreasing thorax volume
- Decrease in thorax volume increases pressure in lungs
- Pulmonary pressure is greater than atmospheric pressure and air is forced out
What is pulmonary ventilation rate?
Total volume of air moved into the lungs in one minute
What is tidal volume?
Volume of air taken in at each breath when the body is at rest
What is breathing rate?
Number of breaths per minute
PVR equation:
PVR = tidal vol x breathing rate
Adaptations of lungs/alveoli for efficient gas exchange
- Walls of alveoli and alveolar capillaries are only one cell thick for a short diffusion distance
- RBCs are slowed as they pass alveoli allowing more time for diffusion
- RBCs flattened against capillary walls for short diffusion distance
- Large surface area of alveoli due to many folds and lots of alveolar capillaries means rich blood supply
- Lungs are constantly ventilated and blood is constantly circulating maintaining a steep concentration of gradient
Ventilation in fish and how it results in efficient uptake of oxygen
- filaments and lamellae for large SA
- large number of capillaries to maintain a gradient/remove oxygen
- Pressure changes as fish opens mouth which brings more water in/maintains gradient
- thin epithelium for short diffusion pathway
- countercurrent flow maintains a concentration gradient across the whole length of the gill
What happens to the concentration of oxygen in water as the temperature rises?
It decreases as less oxygen dissolves into the water
What happens to the rate of ventilation in fish at higher temps and why?
It increases because the concentration of oxygen decreases so they need to pass more water over their gills to have sufficient amounts of oxygen for respiration.
Explain two ways in which the structure of the gills is adapted for efficient gas exchange
- Many filaments/lamellae for large surface area
- Thin epithelium for short pathway
