3.1 - adaptations for gas exchange Flashcards
how does an organisms size relate to its SA:V ratio
larger organism = lower SA:V
how does SA:V affect transport of molecules
lower SA:V = further distance molecules must travel to reach all parts of organism
diffusion alone not sufficient in organisms w/ small SA:V
why do larger organisms require mass transport + specialised gas exchange surfaces
- small SA:V
- diffusion insufficient to provide all cells w/ required O2 + to remove all CO2
- large organisms more active than smaller organisms
four features of an efficient gas exchange surface
- large SA
- short diffusion distance
- steep diffusion gradient
- ventilation mechanism
describe the gas exchange mechanism in amoeba
- unicellular organism w/ large SA:V
- thin cell membrane providing short diffusion distance
- simple diffusion across cell surface membrane sufficient to meet demands of respiratory processes
describe the gas exchange mechanism in flatworms
- multicellular organisms w/ relatively small SA:V (in comparison to amoeba)
- flat surface provides large SA + reduces diffusion distance
- simple diffusion sufficient to meet demands of respiratory processes
describe the gas exchange mechanism in earthworms
- cylindrical, multicellular organisms w/ relatively small SA:V (in comparison to flatworms)
- slow moving + low metabolic rate (require little O2)
- rely on external surface for gas exchange
- circulatory system transports O2 to tissues + removes CO2, maintaining steep diffusion gradient
define ventilation
movement of fresh air into a space + stale air out of a space to maintain a steep conc gradient of O2 + CO2
name the organ of gaseous exchange in fish
gills
what are gill filaments
- main site of gaseous exchange in fish, over which water flows
- overlap to increase resistance to flowing water, slowing it down + maximising gaseous exchange
- found in large stacks (gill plates) + have gill lamellae which provide large SA + good blood supply for exchange
explain the process of ventilation in bony fish
- buccal cavity volume increases + pressure decreases to enable water to flow in
- contraction of buccal cavity forces water across gills
- pressure in gill cavity rises, opening operculum
- water leaves
how is a steep diffusion gradient maintained across the entire gas exchange surface in bony fish
due to counter current flow
define counter current flow
blood + water flow in opposite direction across gill plate
how does counter current flow maintain a steep diffusion gradient
what’s the advantage of this
- water always next to blood of lower O2 conc
- keeps rate of diffusion constant + enable 80% of available O2 to be absorbed
what type of flow is exhibited in cartilaginous fish
parallel flow
define parallel flow
water + blood flow in same direction across gill plate
compare counter current + parallel flow
counter current:
- blood + water flow in opposite directions
- steep diffusion gradient maintained, allowing diffusion of O2 across whole gill plate
- high rate of diffusion
- more efficient, more O2 absorbed into blood
- found in bony fish
parallel flow:
- water + blood flow in same direction across gill plate
- diffusion gradient not maintained, diffusion of O2 doesn’t occur across whole plate
- lower rate of diffusion
- less efficient, less O2 absorbed into blood
- found in cartilaginous fish, e.g: sharks
name + describe the main features of an insects gas transport system
spiracles - small external openings along thorax + abdomen through which air enters, + air and water leave gas exchange system
tracheae - large tubes extending through all body tissues, supported by rings of chitin to prevent collapse
tracheoles - smaller branches dividing off tracheae
what’s the main site of gas exchange in insects
tracheoles
describe the adaptations of the insect tracheal system to a terrestrial environment
- spiracles can open + close to regulate diffusion
- bodily contractions speed up movement of air through spiracles
- highly branched tracheoles provide large SA
- impermeable cuticle reduces water loss by evaporation
describe ventilation of the tracheal system in insects
- expansion of abdomen opens thorax spiracles (air enters) + closes abdominal spiracles
- compression of abdomen closes thorax spiracles + opens abdominal spiracles (air expelled)
compare gas exchange surface of an active + inactive amphibian
active - has simple lungs
inactive - relies on moist external surface
how are mammals adapted for gas exchange
- alveoli provide large SA + thin diffusion pathway, maximising volume of O2 absorbed from one breath
- have plentiful supply of deoxygenated blood, maintaining step conc gradient
describe the structure of + function of larynx
hollow, tubular structure located at top of trachea involved in breathing + phonation
