3.3.2 Flashcards
Ficks law
Rate of diffusion is proportional to (surface area x conc gradient) / distance which diffusion occurs
How are single celled organisms adapted for gas exchange?
Can exchange gases with environment using cell surface membrane
May have adaptations to increase surface area to volume ratio eg making themselves wide, flat or having many folds
Increases rate of gas exchange and diffusion
What is the diffusion rate of a single celled organism?
Rapid as substances only have to move across one cell membrane
How are diffusion distance and time taken related?
If you double distance for diffusion time taken is squared
What is the gas exchange system of an insect called?
Tracheal system
How does gas enter/exit the tracheal system of an insect?
Holes in exoskeleton along thorax and abdomen called spiracles
Can open and close to allow gas to enter tubes called trachea
Subdivide into tubes of smaller diameter called tracheoles which end at the body cells
How is an insects tracheal system adapted to maximise the rate of diffusion?
Tracheoles have thin walls so short diffusion distance to cells
Highly branched/many tracheoles so short diffusion distance to cells
Highly branched/many tracheoles so high surface area
Fluid in tracheoles moves out during exercise so shorter diffusion distance
Muscles can contract to move air to maintain concentration gradient
Describe gas exchange in a resting insect
Oxygen diffuses down concentration gradient into spiracles then through trachea and tracheoles
Oxygen diffuses into cells to be used up in aerobic respiration
Describe gas exchange in an active insect
Lack of oxygen increases rate of anaerobic respiration in cells increasing lactic acid concentration which decreases water potential of cells causing water to move by osmosis from tracheoles into cells down water potential gradient which decreases diffusion distance increasing rate of diffusion
Describe methods used to prevent water loss in insects
Water in tracheoles to prevent water moving out of cells by osmosis
Spiracles surrounded by small hairs which trap humid air decreasing difference in water potential and reduces air movement
Have a waxy cuticle to prevent water loss
Summarise gas exchange in fish
Oxygenated water enters through mouth
Water passes over gills
Deoxygenated water leaves
Describe how water is moved over the gills
Mouth opens
Lowers floor of mouth, increasing volume and decreasing pressure
Causes oxygenated water to flow in
Mouth shuts
Raises floor of mouth, decreasing volume and increasing pressure
Forces water over gills and out through operculum
Describe how the gills are adapted to have a high surface area
Contain gill filaments which are highly branched and folded thin tissue covered in lamella
Describe the counter current system in gills
Flow of blood and water in lamella are in opposite directions
Blood is always passing water with a higher oxygen concentration
Diffusion gradient is maintained for full length of gill
