Organisms Exchange Substances With Their Environment Flashcards
What is surface area
Total area of the organism that is exposed to the external environment
What is volume
Total internal volume of the organism
what is the relationship between size and SA:V
As the size of the organism increases, the SA:V ratio decreases
What is metabolic demand
How much oxygen and nutrients an organism needs to take in daily to respire enough to maintain the metabolic rate
What is the relationship between SA:V and metabolic rate
as sa:v increases (smaller organisms), metabollic rate increases because:
-rate of heat loss per unit body mass increases
-organism needs a higher rate of respiration to release enough heat to maintain a constant body temperature
what is metabolic rate
The amount of energy expended by that organism within a given period of time
how is surface area to volume ratio calculated
divide surface area (size length x side width x number of sides) by volume (length x width x depth)
explain the adaptations that facilitate exchange as SA:V reduces in larger organisms
changes to body shape
-increases SA:V and reduces long diffusion distance/ pathway
development of specialised surface/ organ for gaseous exchange
-increases SA:V and reduces long diffusion pathway
-maintain a concentration gradient for diffusion
how is the body surface of a single-celled organism aqdapted for gas exchange
-thin, flat shape and large surface to volume ratio
-short diffusion distance to all parts of cell so rapid diffusion
describe the tracheal sytem of an insect
- spiracles (pores on the surface that can open and close to alllow diffusion)
-trachea ( large tubes full of air that allow diffusion)
-tracheoles (smaller branches from trachea, permeable to allow gas exchanges with cells)
how is an insects tracheal system adapted for gas exchange
tracheoles have thin walls
- short diffusion pathway- rapid gas exchange
high numbers of highly branched bronchioles
- short diffusion distance to cells, rapid gas exchange
- large surface area
contraction of abdominal muscles (abdominal pumping) changes pressure in body, causing air to movr in/ ojut
- maintains concentration gradient
fluid in end of tracheoles drain into tissues by osmosis during exercise
- diffusion is faster, short diffusion pathway into respiring tissues
explain structural and functional compromises in terrestrial (land) insects that allow efficient gas exchange while limiting water loss
- thick waxy cuticle , increases diffusion distance so less watser loss by evaporation
- spircales can open to allow gas exchange and close to reduce water loss
-hairs around spiracles, trap moist air, less water loss
explain how the gills of fish are adapted for gas exchange
made of many filaments covered in many lamellae
-increase surface area for diffusion
thin lamellae wall/ epithelium
- short diffusion pathway between water and blood
lamellae have a large number of capillaries
-remove O2 and bring CO2 quickly so maintains concentration gradient
countercurrent flow:
-blood and water flow in opposite directions through or over lamellae
-oxygen concentration always higher in water than blood
-maintains a concentration gradient of O2 between water and blood for diffusion along whole length of lamellae
why is parallel flow not suitable for gills
equillibrium would be reaches so oxyge wouldn’t diffuse into blood along whole gill plate
explain how the leaves of plants are adapted for gas exchange
high density of stomata
-large surface area for gaseous change
spongy mesophyll contains air sacs
-large surface area for gases to diffuse through
thin
-short diffusioin distance
what is the xerophyte
plant adapted to live in very dry conditions
explain adaptations in xerophytic plants that allow efficient gas exchange whilelimiting water loss
thicker waxy cuticled
-increases diffusion distance, less evaporation
sunken stomata, rolled leaves, hairs on leaves
-trap water vapour, protect stomata from wind
-less evaporation
spines/ needles
-reduces surface area to volume ratio
what is the structure of the human gas exchange system
trachea
bronchi that branch into bronchioles in the lungs
alveoli surrounded by capillaries
what afre essential features of the alveloar epithelium that make it adapted as a surface for gas exchange
flattened cells
-short diffusion distance
folded
-large surface area
pearmeable
-allows diffusion of O2 and CO2
moist
-gases can dissolve for diffusion
good blood supply from large network of capillaries
-maintains concentration gradient
how does gas exchange occur in the lungs
oxygen diffuses from air sacs of alveoli into blood down its concentration gradient
across alveolar epithelium then into capillary endothelium
CO2 diffuses out of the bloodstream into alveoli
-later to be exhaled
explain the importance of ventilation
-brings in air containing higher cocnc of oxygen, removes air with lower conc of oxygen
-maintaining concentration gradient
explain how humans breathe in and out
inspiration
diaphragm muscles contract- flatten
external intercostal muscles contract, internal intercostal muscles relax
ribcage pulled up/ out
increasing volume and decreasing pressure in thorax
air moves into lungs down pressure gradient
expiration
diaphragm relaxes moves upwards
external intercostal uscles relax, internal intercostal muscles contract
ribcage moves down/ in
decreasing volume and incrdeasing pressure in thorax
air moves out of lungs down pressure gradient
why is expiration normally passive at rest
ingternal ingtercostal muscles do not normally need to contract
expiration aided by elstic recoil in alveoli
how do different lung diseases reduce the rate of gas exchange
thickened alveolar tissue, longer diffusion pathway
alveolar wall breakdown, reduces surface area
reduce lung elasticity, lungs expand/ recoil less, reduces concentration gradients
