Gas exchange 6.1 -6.8 Flashcards
How does a thick cuticle limit water loss?
Give an example of a plant that uses this method
Waxy cuticle = waterproof barrier
10% of water loss can occur through this route in regular plants
Thicker cuticle = less water loss
E.g holly
How does rolling up of leaves prevent water loss?
Give an example of a plant that exhibits this
🔹stomata are located on lower epidermis
🔹rolling leaves so that lower epidermis faces in creates a region of trapped still air, this area becomes saturated with water vapour so has high water potential
🔹no water potential gradient between inside and outside of leaf
E.g Marram grass
How do hairy leaves prevent water loss?
Give an example of a plant which uses this method
🔹On lower epidermis hairs trap still, moist air next to leaf surface
🔹Reduces water potential gradient
E.g one type of heather plant
How does the location of stomata in pits and grooves help to limit water loss?
Give an example of a plant that uses this method
Trap still, moist air next to leaf which reduces water potential gradient
E.g pine trees
How do insects limit water loss?
🔹Small SA:Vol
🔹Waterproof
🔹Spiracles
What is tissue fluid?
The environment around the cells of multicellular organisms
What is the relationship between metabolic rate, exchange of materials, and SA:vol
Higher metabolic rate = more exchange of materials = higher SA:vol required
What is passive exchange?
No metabolic energy is required, e.g. osmosis and diffusion.
What is active exchange?
Metabolic energy is required, e.g. by active transport
Why can’t larger organisms rely on diffusion alone for the transport of materials?
Larger organism = smaller SA:vol
What are the features of specialised exchange surfaces?
🔹Large SA:vol
🔹Very thin so that diffusion pathway is reduced
🔹Selectively permeable membrane to allow certain materials to cross
🔹A transport system to ensure the movement of the internal medium e.g. blood, to maintain a diffusion gradient
What is Fick’s law?
SA x difference in concentration/
length of diffusion path
What features of a plant limit water loss?
🔹Thick waxy cuticle 🔹Rolling up of leaves 🔹Hairy leaves 🔹Stomata in pits or grooves 🔹Reduced SA:Vol of leaves
Why do large mammals require the absorption of such a large volume of oxygen?
🔹Large volume of living cells means that a large volume of oxygen is required for respiration
🔹They maintain a high body temp. Which means they require high metabolic and respiratory rates
Why are the lungs an internal structure
🔹They are delicate and require protection from the rib cage
🔹The body as a whole would lose a lot of water and dry out
List the sequence of all the structures which air passes through
1) nose
2) trachea
3) bronchi
4) bronchioles
5) alveoli
What supports the trachea and why?
Cartilage
To prevent the trachea collapsing as the air pressure inside falls when breathing
What do the tracheal walls consist of?
Muscle, lined with ciliated epithelium and goblet cells
What is the function of goblet cells?
Produce mucus to trap dirt particles
What is the function of cilia?
Small hairs which move dirt laden mucus out of the airway so that they stay away from the lungs
Why are there elastic fibres between the alveoli?
Allow the alveoli to stretch as they fill with air when breathing in.
They then spring back during exhalation I’m order to expel carbon dioxide.
Why is diffusion of gases between alveoli and blood so fast?
🔹RBCs move slowly through capillaries
🔹RBCs are flattened against capillary walls reducing diffusion distance
🔹alveoli and capillaries are just 1 cell thick, reducing diffusion distance
🔹pulmonary capillaries and alveoli have a large SA
🔹concentration gradient is maintained by constant ventilation, heart pumping blood around body, and blood flow through pulmonary capillaries
Describe how countercurrent flow maximises exchange (3)
🔹The flow of water is in the opposite direction to the flow of blood
🔹This maintains a concentration gradient across the entire length of the lamellae so diffusion can occur constantly
🔹which maximises exchange
🔹
How do bony fish ventilate their lungs?
What happens to fish who cannot rely on this method of ventilation?
Using muscular contractions which cause water to move through the mouth over gills and out of the open opercula
Other fish ventilate gills by constant flow of water over them, meaning they must maintain a forward motion. If not they die.
