3. Exchange Flashcards
What is the relationship between the size of the organism and sa:v ratio?
The smaller the organism, the larger the sa: v ratio
What are the features of specialised exchange surfaces?
- large sa to v ratio increases the rate of exchange
- very thin = diffusion pathway is short
- selectively permeable to allow selected materials to cross
- movement of environmental medium to maintain diffusion gradient
What is Ficks law?
Rate of diffusion= surface area x concentration difference/ diffusion distance
What is the relationship between surface area to volume ratio and metabolic rate?
Smaller organisms have a larger surface area to volume ratio which means they lose heat quicker
How do single celles organisms exchange substances?
They are small and have a large sa: v ratio
Oxygen is absorbed by diffusion across body surface
CO2 diffuses out across the body surface
How are insects adapted for efficient gas exchange?
- contain tracheae
- divide into tracheoles, it brings oxygen directly to respiring tissue
- there is a short diffusion pathway from the tracheole to any body cell
What three ways do respiratory gases move in and out of the tracheal system?
- along a diffusion gradient
- oxygen concentration at the end of tracheoles falls when being used for respiration, CO2 is produced by respiration, creates diffusion gradient in the opposite direction
- mass transport
- contraction if muscles squeezes trachea for aid to move in and out
- ends of tracheoles are filled with water
- lactate is produced in the cells, water moves in and out, draws more air in, diffusion is rapid
How are fish adapted for efficient gas exchange?
- contain many gill filaments which contain many gill lamellae
- increases surface area
- gill lamellae are at right angles which creates a short diffusion pathway
Describe the structure of the gills
- located within the body of the fish
- girls are developed to extract dissolved oxygen from the water
- made of gill filaments stacked together
- gills are extremely thin, cannot support themselves and stick together without water
What is the countercurrent flow?
Where the flow of water and blood are in opposite directions
What does this mean?
- maximises O2 uptake and increases gas exchange by ensuring good diffusion gradient along the width of the lamellae
- makes sure blood meets water with lots of oxygen so oxygen can diffuse from high conc in the water to a lower conc in the blood
What is the movement of water inside a fish?
- operculum closed
- mouth open
- floor of mouth lowers causing buccal cavity to be larger increasing the sa: v
- pressure is lower in the mouth compared to outside, water therefore enters down a concentration gradient
- opercular cavity bulges causes a slight pressure drop, water enters the opercular cavity from the mouth
What is the movement of water out?
- operculum opened
- mouth closes
- floor of the mouth raised which increases pressure
- water is forced out
- maintains a flow of water over the gills
How are plants adapted for efficient gas exchange?
- air spaces in the leaf have a large surface area
- many stomata, no cell is far away from stoma, the diffusion pathway is short
- interconnecting air spaces occur through mesophyll, gases can come into contact with them
- large sa of mesopgyll means there is rapid diffusion
How does the stomata open and close?
- each stoma is surrounded by guard cells
- these open and close the stomatal pores
- controls the rate of gaseous exchange
- tries to prevent water loss
What are adaptations do xerophytic plants have to try and limit water loss?
- they cannot have a small sa: v ratio as they need to conduct photosynthesis meaning it has to be large to attract light
- water proof coverage and stomata to limit water loss
- thick cuticle, the thicker the less is lost
- hairy leaves, traps moist air, less water is lost through evaporation
- rolling of leaves, protects stomata, traps moist air and becomes saturated with water vapour, no water potential gradient meaning none is lost
What are the lungs protected by?
The ribs
What is the trachea?
A flexible airway
Supported by rings of cartilage
What is the bronchi?
Produce mucus
Contain cilia
What are bronchioles?
Increase sa
They control the flow of air in and out of the alveoli
What is the alveoli?
They fill with air
They contain elastic fibres to stretch
What is inspiration?
Inhalation
What is expiration?
Exhalation
What is the process of inspiration?
External intercostal muscles contract
Ribs are pulled upwards and outwards
Diaphragm contacts and flattens
Increase in volume in the lungs
Decrease in pressure in the lungs
Atmospheric pressure is now greater outside the lungs than in, so air is forced in
