Adaptations for Gas Exchange Flashcards
What is the relationship between the size of an organism/structure + its SA:V ratio?
- small organisms = larger SA:V ratio so has a large SA for absorption of nutrients + gases + secretion of waste + a small V so has a shorter diffusion distance
- large organisms = smaller SA:V ratio so has a small SA for absorption of nutrients + gases + secretion of waste + a large V so has a longer diffusion distance
How have larger organisms adapted to facilitate exchange of substances?
- they have a large variety of specialised cells, tissues, organs + systems required to supply O2 to body for ATP production, + remove CO2 from body bc it’s a waste product
What is the relationship between SA:V ratio + metabolic rate?
- larger animals have a higher metabolic rate
- but smaller animals have a higher BMR per unit of body mass bc have a larger SA:V ratio so lose more heat = use more energy to maintain body T°C
What do effective exchange surfaces in organisms have?
- a large SA
- short diffusion distance
- maintained conc gradient
Describe the adaptations to gas exchange surfaces across body surface of a single celled organism.
- has large SA:V ratio allowing exchange of substances to occur via simple diffusion bc has a short diffusion distance
How have insects adapted to facilitated rapid gas exchange?
- spiracles: valve like openings in exoskeleton allowing O2 + CO2 to enter + leave tracheal system
- trachea branching off into tracheoles: internal tubes w chitin rings (to keep them open) that extend throughout all tissues in insect so O2 can diffuse directly into respiring cells
What 3 methods move gases into + out of the tracheal system of insects?
- along a diffusion gradient
- mass transport
- the ends of the tracheoles are filled w water
Describe how gases move into + out of the tracheal system along a diffusion gradient.
- when cells respire, O2 is used up at ends of tracheoles creating a conc gradient allowing atmospheric O2 to diffuse along tracheae to cells
- CO2 is also produced, creating a conc. gradient in opposite direction, so diffuses across tracheae from cells to atmo.
Describe how gases move into + out of the tracheal system by mass transport.
- when an insect contracts + relaxes their abdominal muscles, it squeezes the trachea, allowing mass movements of air in + out, speeding up gas exchange
Describe how gases move into + out of the tracheal system by having water at ends of tracheoles.
- when muscle cells respire anaerobically + produce lactate, it lowers water potential in cells
- causing water to move from tracheoles into cells by osmosis
- this dec. volume in tracheoles so more air from atmo is drawn in + allows gases to diffuse across more quickly
Describe the adaptations to gas exchange surfaces in the tracheal system of an insect.
- large NO° of fine tracheoles to inc SA
- thin tracheole walls + short distance between spiracles + tracheoles = short diffusion distance
- use of O2 + production of CO2 creates steep diffusion gradients
How have fish adapted to facilitated rapid gas exchange?
- have 4 layers of gills on each side of head
- each gill arch is attached to 2 stacks of gill filaments
- at right angles to gill filament are many gill lamellae, which inc SA
Describe the adaptations to gas exchange surfaces of gills in fish.
- many gill filaments covered in gill lamellae to inc SA
- thin lamellae containing network of capillaries to create a short diffusion distance
- countercurrent flow, which is when water flows over gills in opposite direction to blood flow in capillaries, to maintain a steep conc gradient across entire lamellae surface
What is the equation used to calculate the rate of diffusion?
- rate of diffusion = SA x conc difference / thickness of surface
How are leaves of dicotyledonous plants adapted to facilitated rapid gas exchange?
- air spaces in spongy mesophyll inc SA
- thin leaves: inc SA:V ratio so shorter diffusion distance
Describe the adaptations to gas exchange surfaces of leaves of dicotyledonous plants.
- stomata on bottom of leaf, surrounded by guard cells, control diffusion of gases into + out of leaf
- turgid guard cells causes stomata to remain open so CO2 can diffuse into leaf to be used in photosynthesis, which maintains conc gradient + so O2 (waste product) can diffuse out
- shrunken guard cells causes stomata to close + occurs at night (no photosynthesis) to reduce water loss by evaporation
Explain the compromises between efficient gas exchange + limiting water loss in terrestrial insects.
- small SA:V ratio where water can evaporate from
- have a waterproof exoskeleton made of chitin w a lipid layer: makes gas exchange by diffusion hard (so has tracheal system) + prevents water loss
- spiracles: open + close to dec. water loss
Explain the compromises between efficient gas exchange + limiting water loss in xerophytic plants.
- curled leaves/sunken stomata/hairs surrounding stomata: trap moisture to lower water potential gradient so less water lost via stomata
- thicker waxy cuticle: dec. evaporation
- longer root network: to reach more water
- fewer stomata
