3.1 and 3.2 Flashcards
Describe the relationship between the size and structure of an organism and its surface area to volume ratio:
As size increases, SA:V tends to decrease
More thin/flat/folded/elongated structures increase SA:V
Why calculate SA:mass for organisms instead of SA:V?
Easier/quicker to find/more accurate because irregular shape
What is metabolic rate?
Amount of energy used up by an organism in a given period of time
Often measured by oxygen uptake as used in aerobic respiration to make ATP for energy release
Explain the relationship between AA:V and metabolic rate:
As SA:V increases, metabolic rate increases because:
- rate of heat loss per unit body mass increases
- so organisms need a higher rate of respiration
- to release enough heat to maintain a constant body temp
Explain the adaptation that facilitate exchange as SA:V reduces in larger organisms
Changes to body shape increases SA:V and overcomes long diffusion distance
Development of systems, such as specialised surface/organ for gaseous exchange e.g. lungs, increases SA:V and overcomes long diffusion distance and maintains a concentration gradient for diffusion
How is the body surface of a single celled organism is adapted for gas exchange?
Thin, flat shape and large surface area to volume ratio
Short diffusion distance to all parts of cell- rapid diffusion of O2/CO2
Describe the tracheal system of an insect:
Spiracles- pores on surface that can open/close to allow diffusion
Tracheae- large tubes full of air that allow diffusion
Tracheoles- smaller branches from tracheae, permeable to allow gas exchange with cells
Explain how an insects tracheal system is adapted for gas exchange:
Tracheoles have thin walls, so short diffusion distance to cells
High numbers of highly branched tracheoles so short diffusion distance to cells and large surface area
Tracheae provide tubes full of air sp fast diffusion
Contraction of abdominal muscles changes pressure in body causing air to move in/out to maintain conc. gradient
Fluid in end of tracheoles drawn into tissues by osmosis during exercise- diffusion is faster through air
Explain structural and functional compromises in terrestrial insects that allow efficient gas exchange while limiting water loss:
Thick waxy cuticle/ exoskeleton - increases diffusion distance so less water is lost
Spiracles can open to allow gas exchange and close to reduce water loss
Hairs around spiracles- trap moist air, reducing water potential gradient so less water loss
Explain how the gills of fish are adapted for gas exchange:
Gills made of many filaments covered with many lamellae to increase surface area for diffusion
Thin lamellae wall/ epithelium so short diffusion pathway between water/blood
Lamellae have large number of capillaries to remove O2 and bring CO2 quickly so maintains conc. gradient
Describe the counter current flow system:
Blood and water flow in opposite directions through/over lamellae
So oxygen conc. always higher in water than blood
So maintains a conc. gradient of O2 between water and blood
Diffusion along whole length of lamellae
Explain how the leaves of dicotyledonous plants are adapted for gas exchange
Many stomata (high density) so large SA for gas exchange
Spongy mesophyll contains air spaces so large SA for gases to diffuse through
Thin so short diffusion distance
Define xerophyte
Plant adapted to live in very dry conditions
Explain structural and functional compromises in xerophytic plants that allow gas exchange while limiting water loss:
Thicker waxy cuticle increases diffusion distance so less evaporation
Sunken stomata in pits/rolled leaves/hairs to trap water vapour and reduce water potential gradient so less evaporation
Spines/needles reduces surface area to volume ratio
Describe the gross structure of the human gas exchange system
Trachea
Bronchi
Bronchioles
Alveoli
Explain the essential features of the alveolar epithelium that makes it adapted as a surface for gas exchange:
Flattened cells/1 cell thick so short diffusion distance
Folded so large SA
Permeable so allows diffusion of O2/CO2
Moist so gases can dissolve for diffusion
Good blood supply from large capillary network maintains conc. gradient
Describe how gas exchange occurs in the lungs:
Oxygen diffuses from alveolar air space into blood down its conc. gradient across alveolar epithelium then across capillary endothelium
Explain the importance of ventilation:
Brings in air containing higher conc. of oxygen and removes air with lower conc. of oxygen maintaining conc. gradients
Describe inspiration:
Diaphragm muscles contract
External intercostal muscles contract, internal intercostal muscles relax so ribcage pulled up/out
Increasing volume and decreasing pressure (below atmospheric) in thoracic cavity
Air moves into lungs down pressure gradient
Describe expiration:
Diaphragm muscles relax
External intercostal muscles relax, internal intercostal muscles contract so ribcage moves down/in
Decreasing volume and increasing pressure (above atmospheric) in thoracic cavity
Air moves out of lungs down pressure gradient
Suggest why expiration is normally passive at rest:
Internal intercostal muscles do not normally need to contract
Expiration aided by elastic recoil iin alveoli
Suggest how different lung diseases reduce the rate of gas exchange
Thicker alveolar tissue (e.g. fibrosis) - increases diffusion distance
Alveolar wall breakdown- reduces surface area
Reduce lung elasticity- lungs expand/recoil less- reduces conc gradients of O2/CO2
Suggest how different lung diseases affect ventilation:
Reduce lung elasticity (e.g. fibrosis- build up of scar tissue) - lungs expand/recoil less, reducing volume of air in each breath (tidal volume) and reducing max. volume of air breathed out in one breath (forced vital capacity)
Narrow airways/reduce airflow in/out of lungs (e.g asthma- inflamed bronchi) - reducing max volume of air breathed out in one second (forced expiratory volume)
Reduced rate of gas exchange- increased ventilation rate to compensate for reduced oxygen in blood
Suggest why people with lung disease experience fatigue
Cells receive less oxygen so rate of aerobic respiration is reduced and less ATP is made
