Adaptations for gas exchange in animals

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What do the gills of a fish, the alveoli and the spongy mesophyll cells in leaves have in common?
They are all excellent gas exchange surfaces, they allow quick and efficient gas exchange between the cells of the organism and the enviroment
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What features do gas exchange surfaces have in common?
Large surface area to volume ratioover which gas exchange can take place rapidly, They are think so there is a short diffusion pathway, Moist surface where gases can dissolve first before they diffuse, maintain a high conc. gradient
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What is the gas exchange surface for unicellular organisms?
The plasma membrane
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What type of surface area to volume ratio do unicellular organisms have?
A high one
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Why is the maximum size of unicellular organism about 100um?
The oxygen demand is proportional to the volume, the ability to absorb oxygen is proportional to the SA. Therefore the SA to V ratio must be large enough to meet the oxygen demand of the organism. The diffusion distance also needs to be short.
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What is more efficient for gas exchange, a cube-shaped or a tubular shape?
A tubular shape
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Do multicellular organisms have a high or low surface area to volume ratio?
A low one
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How have flatworms overcome the problem of being multicellular?
They have a flat body to give them a larger surface area to volume ratio
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Explain the features of an earthworm which show they have adapted to being multicellular
It's skin is the respiratory surface which is kept moist with mucus, It moves slowly and has a low metabolic rate so has a low oxygen requirement, haemoglobin is in its blood carrying oxygen around in blood vessels maintaining a diffusion gradient
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What are some problems that terrestrial organisms must overcome?
Water evaporates from the body surfaces which could result in dehydration, gas exchange surfaces need to be moist so they are likely to lose a lot of water.
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How do insects reduce water loss?
By having an exoskeleton which is rigid and comprises a thin waxy layer
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Where does gas exchange occur in insects?
Through paired holes called spiracles running along the side of the body
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What are the branched tubes that spiracles lead to?
Tracheae and then into smaller tubes called tracheoles
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How is water loss reduced by insects?
They open and close
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What do some insects have to help reduce water loss?
Hairs covering their spiracles
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What and how ventilates the tracheae?
The abdomen by periods of activity such as flying
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What are at the end of tracheoles?
Fluid filled sacs that are close to muscle fibres
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Where does gas exchange take place in insects?
At the interface between tracheoles and muscle fibres
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What are fish's gas exchange surface?
The gills
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What do gills have that make it an efficient gas exchange surface?
A one-way current of water kept flowing by a special ventilation mechanism, many folds that provide a large surface area, a large surface area maintained as the density of water flowing through prevents the gills from collapsing
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What are the two main types of fish?
Cartilaginous and bony
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What must cartilaginous fish keep doing?
They must keep swimming to force water over the gills
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In cartilaginous fish, what directions to the blood and water flow?
In the same direction i.e. parallel flow
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For how long can diffusion via parallel flow continue?
Until equilibrium is met
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In bony fish, what is the name of the flap that covers the gills?
The operculum
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What is each gill supported by?
A gill arch
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What are the projections along the gill arch called?
Gill filaments
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What is the name of the gas exchange surfaces on the gill filaments?
Gill lamellae
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How are gill filaments held apart?
By water flowing between them
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What is the space between the operculum and the gills called?
The opercular cavity
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How does the opercular cavity play a part in the fish's ventilation mechanism?
The operculum can snap shut against the side of the fish or open, controlling the movement of water in and out of the opercular cavity
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How is water taken in by a fish?
The mouth opens, the operculum closes, the floor of the mouth is lowered, the volume inside the mouth increases therefore pressure decreases so water flows in
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How is water forced over the gills?
The mouth closes, the operculum closes, the floor of the mouth is raised, the volume inside decreases, the pressure inside therefore increases, water flows over the gills due to this pressure
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In bony fish, what directions do blood and water flow?
In opposite directions, i.e. a counter current flow
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Why is this more efficient than a parallel flow?
The water is therefore always at a higher concentration in oxygen than the blood so oxygen diffuses across the whole length of the gill lamellae
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What causes air to rush into your lungs in reference to pressure?
Air is drawn into the lungs by reducing the pressure inside to below atmospheric pressure
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What causes air to rush out of your lungs in reference to pressure?
Air is blow out of the lungs by increasing pressure inside them to above atmospheric pressure
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How is the pressure in the lungs made to be lower than atmospheric pressure?
The external intercostal muscles (I-M) contract and the internal I-M relax, raising the ribcage up and out, the diaphragm contracts and flatterns, both these actions increase the volume and hence causes pressure to decrease.
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How is the pressure in the lungs made to be higher than atmospheric pressure?
The external intercostal muscles (I-M) relax and the internal I-M contract, lowering the ribcage downwards and inwards, the diaphragm relaxes and bulges upwards, both these actions decrease the volume and hence causes pressure to increase.
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What is around each lung and lining the thorax?
Pleural membranes
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What is the space between the two pleural membranes of the lungs and thorax called?
Pleural cavity
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What is in the pleural cavity?
Pleural fluid
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What is the function of the pleural fluid?
It acts as a lubricant and allows friction free movement of the lungs against the inner wall of the thorax
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What don't the alveoli collapse when we breathe out?
They have an anti-sticking chemical called a surfactant
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What does the surfactant do?
It reduces the surface tension and keeps the alveoli open
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Why do we use artificial surfactants?
To assist breathing in premature babies
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What is the job of the capillaries around the alveoli?
To provide efficient blood transport of gases
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Why is expired air saturated with water?
The lungs are full of water
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When exhaled, the nitrogen % is the same as when inhaled why is this?
Gaseous nitrogen isn't used by the body
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What are the trachea, bronchi and bronchioles lined with?
Ciliated epithelial cells
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What are the job of ciliated epithelial cells?
After dust and pathogens have been trapped in mucus, the cilia beat to move a stream of mucus up your throat.
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What is a spirometer?
It's a piece of apparatus used to measure to volume of air that moves in and out of the lungs
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Where are the changes of breath recorded?
On a kymograph
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What is the presence of soda lime for in a spirometer?
To absorb carbon dioxide
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What is tidal volume?
The volume of air breathed in and out during a single breath.
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What is vital capacity?
The maximum volume of air that can be breathed in or out of the lungs
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What is inspiratory reserve volume?
The additional amount of air that can be breathed in after a person has breathed in normally
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What is expiratory reserve volume ?
The additional amount of air that can be breathed out after a person has breathed out normally
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What is the residual volume?
The amount of air that cannot be expelled from the lungs however deeply a person breathes out
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How do you use a spirometer?
The mouth is sterilized to prevent the spread of diseases, oxygen in the space is replenished so tht the subject gets enough to prevent damage to cells, soda lime needs to be present to remove CO2.
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Card 2

Front

What features do gas exchange surfaces have in common?

Back

Large surface area to volume ratioover which gas exchange can take place rapidly, They are think so there is a short diffusion pathway, Moist surface where gases can dissolve first before they diffuse, maintain a high conc. gradient

Card 3

Front

What is the gas exchange surface for unicellular organisms?

Back

Preview of the front of card 3

Card 4

Front

What type of surface area to volume ratio do unicellular organisms have?

Back

Preview of the front of card 4

Card 5

Front

Why is the maximum size of unicellular organism about 100um?

Back

Preview of the front of card 5
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