Gas exchange Flashcards
how are single celled organisms adapted for gas exchange (3)
High surface area to volume ratio
short diffusion pathway
high metabolism rate
how are fish adapted for gas exchange (3)
- Large surface area - gills are the organ of gas exchange (operculum skin covers gills) Many gill filaments with many microscopic lamellae
- Short diffusion pathway - thin epithelial walls of gills and capillaries are one cell thick
- Steep concentration gradient - Counter-current flow
counter-current flow vs parallel flow
Water containing oxygen flows continually through the mouth and over gills
Blood in the blood capillaries flows in the opposite direction maintains a steep concentration gradient
Allows diffusion across the whole length of the gill so almost all oxygen is diffused into the blood
Parallel flow would create an equilibrium where diffusion stops
how are insects adapted to gas exchange (5)
• Have many spiracles on the side of the body surface
Valve opens and closes so there is water loss
Tracheae divide into tracheoles which extend throughout the body tissues
• Gases diffuse along a diffusion gradient
Respiring cells use O2 and produce CO2 creating a concentration gradient
More rapid diffusion in air than water
- Mass transport – contraction of muscles squeezes the trachea so gases move in and out
- Ends of tracheoles are filled with water
- Short diffusion pathway (small insects)
how does the ends of tracheoles being filled with water aid the gas exchange in insects
Anaerobic respiration produces soluble lactate which lowers water potential causing water to move into cells by osmosis which draws air in creating more rapid diffusion
how are plants adapted for gas exchange
- Enter through stomata that open and close by guard cells down concentration gradient
- Spongey mesophyll layer has a large surface area for rapid diffusion and constant contact with gases
how are xerophytes adapted to limit their water loss (5)
- Thick waterproof cuticle
- Stomata located in pits/ grooves to trap moist air and closes to prevent water loss by evaporation
- Rolling up of leaves - lower epidermis is inside so traps air that is saturated with water vapour
- Hairy leaves traps still, moist air which reduces water potential gradient
- Small surface area to volume ratio leaves
how are insects adapted to limit their water loss (3)
- Small surface area to volume ratio
- Waterproof cuticle covering the rigid outer skeleton made of chitin
- Spiracles close during rest when less O2 is needed
adaptations of alveoli (3)
• Large total surface area (alveolar epithelium)
• Steep concentration gradient
o Blood flows and takes O2 away
o Breathing in a high concentration of O2
• Short diffusion pathway
o Rich blood supply so closely associated with blood capillaries
Red blood cells are flattened against capillary walls to reduce length of diffusion pathway
o Blood capillaries and alveoli are one cell thick
breathing in (4)
- Diaphragm contracts and flattens
- External intercostal muscles contract so ribcage moves up and out
- Causes lung volume to increase and pressure to decrease
- Air rushes into lungs to equalise the pressure
breathing out (4)
- Diaphragm relaxes and becomes dome shaped
- External intercostal muscles relax so ribcage moves down and in
- Causes lung volume to decrease and pressure to increase
- Air rushes out to equalise the pressure
pulmonary ventilation rate
total volume of air moved into the lungs in a minute
tidal volume
volume of air normally taken in per breath
breathing rate
number of breaths taken per minute
equation involving breathing rate, pulmonary ventilation rate and tidal
Pulmonary ventilation rate = tidal volume x breathing rate
