3.1,3.2

Question 1

surface area to volume ratio

Answer 1

as the size increases, SA:V decreases
having a thinner structure increases your surface area to volume ratio

Question 2

what is the metabolic rate

Answer 2

amount of energy used by an organism in given period of time
often measured by oxygen uptake as used in aerobic respiration to make ATP for energy release.

Question 3

relationship between sa:v and the metabolic rate

Answer 3

as sa:v increases metabolic rate increases
rate of heat loss per unit of body mass increases
so organisms need a higher rate of respiration
to release enough heat to maintain a constant body temp

Question 4

adaptations which facilitate exchange in larger organisms with smaller sa:v

Answer 4

longer and thinner body shape which increases sa:v and reduces long diffusion pathway
develop specialised surface for gaseous exchange
maintain a conc gradient for diffusion

Question 5

tracheal system of insect

Answer 5

spiracles - pores on surface which can open and close to allow diffusion
trachea large tubes full of air allowing diffusion
tracheoles smaleer branches permeable to allow gas exchange within cells

Question 6

how as insects tracheal system adapted for gas exchange

Answer 6

tracheoles - thin walls so short diffusion distance to all cells
high numbers of branched tracheoles so short diffusion distance to all cells and a large surface area
contraction of abdominal muscles changing pressure in body causing air to move in and out

Question 7

structural compromises in terrestrial insect allowing effect gas exchange and limit water loss

Answer 7

thick waxy cuticle increase diffusion distance so less water loss
spiracles can open and close allow gas exchange and close to reduce water loss
holes around spiracles trap moist air reducing the WPG

Question 8

gills of fish adaption for gas exchange

Answer 8

gills made of many filaments covered in lamellae increasing the surface area for diffusion
thin lamellae wall so short diffusion distance between water and blood
lamellae have a large number of capillaries so remove o2 and bring c02 quickly so maintains a concentration gradient

Question 9

counter current flow

Answer 9

blood and water flow in opposite directions over lamellae
so oxygen concentration always higher in water than blood nearwe
maintaining a conc gradient of o2 between water and blood
for diffusions along whole length of lamallae

Question 10

what would happen if parallel flow in fish

Answer 10

equilibrium would be reached so oxygen wouldn’t diffuse into blood along whole length of gill plate

Question 11

leaves of dicotyledons plants adapted for gas exchange

Answer 11

many stomata so high density large surface area for gas exchange
spongy mesophyll contains air spaces large surface area for gases to diffuse though
thin so short diffusion distance

Question 12

xerophytes

Answer 12

thick waxy cuticle increases the diffusion distance so less evaporation
sunken stomata in pis trapping water vapour so reduced water potential gradient between leaf and air so less evaporation
spines and needles reduce SA:v

Question 13

alveolar epithelium making it adapted for gas exchange

Answer 13

flattened 1 cell thick short diffusion distance
folded for a large surface area
permeable allowing diffusion of 02 and c02
most so gases can dissolve for diffusion
good blood supply from large network of capillaries maintaining a conc gradient

Question 14

how does gas exchange occur in lungs

Answer 14

oxygen diffuses from alveolar air space into blood down its conc gradient
across alveolar epithelium then across capillary endothelium

Question 15

importance of ventilation

Answer 15

bring in air containing a high conc of oxygen and remove air with low conc of oxygen
maintaining a conc gradient

Question 16

inspiration which is breathing in

Answer 16

diaphragm muscles contract flattening
external intercostal muscles contract
internal intercostal muscles relax
ribcage pulled up and out
increasing volume and decreasing pressure in thoracic cavity
air moves into lung down pressure gradient

Question 17

expiration

Answer 17

breathing out
diaphragm relaxes moving upwards
external intercostal muscles relax
internal intercostal muscles contract
ribcage moves down and in
decrease in volume and increase in pressure in thoracic cavity
air moves out of lungs down pressure gradient

Question 18

why is expiration normally passive at rest

Answer 18

internal intercostal muscles donate normally need to contract
expiration aided by elastic recoil

Question 19

how does lung disease reduce rate of gas exchange

Answer 19

thickened alveolar tissue increasing the diffusion distance
alveolar wall breakdown reducing the surface area
reduced lung elasticity lung expand and recoil less and reduces the concentration gradient of o2 and co2

Question 20

how can lung disease affect ventilation

Answer 20

reduces lung elasticity so lungs expand and recoil less reducing the volume air in each breath (tidal vol) and reducing maximum volume if air breathed out in a breath forced tidal capacity
narrow airway reduced airflow out lungs ASTHMA reducing max vol of air breathed out in a second

Question 21

why do ppl with lung disease experience fatigue

Answer 21

cells receive less oxygen
rate of aerobic respiration reduced
less ATP made

Question 22

how to interpret data

Answer 22

describe the overall trend positive or negative correlation between risk fact and incidence of disease
calc percentage change
interpret standard deviation overlap suggest due to chance

Question 23

correlation coefficient

Answer 23

association between 2 data sets

Question 24

t test

Answer 24

comparing 2 mean sets of data

Question 25

chi squared

Answer 25

categorical data

Question 26

Evaluate

Answer 26

samplesize
diversity sex age ethnicity health issues
control variables health and previous medication
duration of study long enough to show LT effects

Question 27

how does reduced tidal volume affect exchange of co2 between blood and alveoli

Answer 27

more co2 remains in blood
so reduces conc gradient
more co2 remains in blood

Question 28

fish gas exchange
system is more efficient than the human gas exchange system.

Answer 28

in fish blood leaving has more oxygen than water leaving
but in humans air leaving has a higher o2 conc than blood

Question 29

explain why plants
grown in soil with very little water grow only slowly.

Answer 29

stomata close
less co2 uptake so less photosynthesis

Question 30

Describe the gross structure of the human gas exchange system

Answer 30

trachea bronchi bronchioles alveoli

Question 31

Explain three ways in which an insect’s tracheal system is adapted for
efficient gas exchange.

Answer 31

Tracheoles have thin walls so short diffusion distance to cells;
Highly branched / large number of tracheoles so short diffusion
distance to cells;
Tracheae provide tubes full of air so fast diffusion (into insect
tissues)