GAS EXCHANGE

Question 1

What adaptations do gas exchange surfaces have

Answer 1

1) large surface area

2) thin - for a short diffusion pathway

Question 2

Where do single celled organisms exchange gases across

Answer 2

their body sirfaces

Question 3

What process do single celled organisms use to absorb and release gases

Answer 3

diffusion

Question 4

Where do single celled organisms diffuse gases in and out of

Answer 4

their outer sirface

Question 5

How are single celled organisms adapted for gas exchange

Answer 5

1) large surface area: volume

2) thin

Question 6

Why do single celled organisms have no need for a gas exchange system

Answer 6

oxygen can take part in biochemical reactions as soon as it diffuses into the cell

Question 7

What is the internal network of tubes called for gas exchange inside an insect

Answer 7

tracheae

Question 8

How are the tracheae supported and why

Answer 8

strengthened rings to stop them collapsing

Question 9

What is the tracheae divided into

Answer 9

smaller dead-end tubes called tracheoles

Question 10

How does air move into the tracheae

Answer 10

pores on surface called spiracles

Question 11

What are tracheoles

Answer 11

smaller tubes that go to individual walls

Question 12

How are tracheoles adapted for gas exchange

Answer 12

thin , permeable walls

Question 13

How do respiratory gases move in and out of tracheal system

Answer 13

1) along a diffusion gradient
2) mass transport
3) end of tracheoles are filled with water

Question 14

Explain respiratory gases move in and out of tracheal system through diffusion gradient

Answer 14

cells are respiring so use up oxygen meaning concentration at end of tubes falls and creates a diffusion gradient & diffusion in occurs.
C02 produced by cells during respiration which creates diffusion gradient in opposite direction & diffuses out

Question 15

Explain respiratory gases move in and out of tracheal system by mass transport

Answer 15

contraction of muscles (rhythmic abdominal movements) can squeeze trachea, meaning mass movement occurs in and out

Question 16

Exlpain respiratory gases move in and out of tracheal system through tracheoles filled with water

Answer 16

muscles around tracheoles respire anaerobically so lactate is produced which is soluble, so lowers water potential of muscle cells = water moves into cells. So volume of tracheal decreases and air drawn in

Question 17

When would tracheoles filled with water occur

Answer 17

during times of major activity

Question 18

How are spiracles opened and closed

Answer 18

by a valve`

Question 19

What are the limitations of the tracheal system

Answer 19

relies on diffusion so needs a short diffusion pathway, meaning size of insects is limited

Question 20

Why have fish deceloped gills

Answer 20

1) waterproof body = gas-tight
2) relatively large SA:V
3) lower concentration of O2 in water than air

Question 21

Where are the gills located

Answer 21

within body of the fish, behind head

Question 22

What are the gills made up of

Answer 22

gill filaments

Question 23

What are at right angles to the gill filaments

Answer 23

gill lamellae

Question 24

What do gill lamellae do

Answer 24

increase the surface area of the gill

Question 25

What system do fish use for gas exchange

Answer 25

counter-current

Question 26

What adaptations do lamellae have to increase rate of diffusion

Answer 26

lots of blood capillaries and thin surface layer = short diffusion pathway

Question 27

What is the counter current system

Answer 27

blood flows in one direction and blood flows in the opposite

Question 28

How does oxygen get to the gills

Answer 28

water containing oxygen enters through fishs mouth and is forced over the gills through openings on each side of its body

Question 29

What does the counter current system ensure

Answer 29

that a large concentration gradient is maintained, allowing for maximum diffusion

Question 30

How does the counter current system work (the countercurrent exhchange principal)

Answer 30

it means that no equilibrium is reached, as the oxygen concentration in the water is always slightly higher than that in the blood so diffusion always occurs

Question 31

Draw the countercurrent flow graph

Answer 31

2 lines going parallel down, one always higher than the other axis : distance along gill plate / saturation with O2

Question 32

Draw the parallel flow graph

Answer 32

2 lines, one going up one going down that meet in the middle to form straight line axis : distance along gill plate / saturation with O2

Question 33

What is the other flow system to countercurrent

Answer 33

parallel flow

Question 34

Which blood flows closest to the lamellae & which direction

Answer 34

deoxygenated, down

Question 35

which blood flows in the centre of the gil l& which direction

Answer 35

oxygenated, up

Question 36

How is gas exchange in plants similar to that pf insects

Answer 36

1) no living cell is far from external air so is near a source of 02/C02 2) diffusion takes place in gas phase (air) so it is more rapid than if it were in water

Question 37

Where does gas exchange for dicotyledonous plants occur

Answer 37

surface of mesophyll cells

Question 38

Where does gas exchange occur for most plants

Answer 38

in the leaves

Question 39

How are leaves adapted for gas exchange

Answer 39

1) many small pores (stomata) and no cell is far from a stomata = short diffusion pathway 2) lots of interconnecting air-spaces that occur throughout mesophyll so gases can readily come in contact with mesophyll cells 3) large SA = rapid diffusion

Question 40

What are the stomata surrounded by

Answer 40

guard cells

Question 41

What do guard cells do and what does this mean

Answer 41

open and close the stomatal pore, means they can control the rate of gaseous exchange

Question 42

Why do they need guard cells

Answer 42

so they can control water loss, through closing them when water loss would be excessive

Question 43

How do guard cells open stomata

Answer 43

increase water content so become turgid and open stomatal pore

Question 44

How do guard cells close stomata

Answer 44

decrease water contenct so become flacid and close stomatal pore

Question 45

Where are mesphyll cells located

Answer 45

between upper and lower epidermis

Question 46

Why do organisms need a method for preserving water

Answer 46

gas exchange requirs thin surface, which increases rate of water loss

Question 47

What adaptations do insects have for conserving water loss

Answer 47

1) smal SA:V - minimise area water is lost from 2) waterproof, waxy outer skeleton (cuticle) over body 3) spiracles - openings around tracheae at body surface which can be closed, so can control water loss 4) hair around spiracles - reduces evaporation

Question 48

What are the waxy cuticles of insects made of

Answer 48

chitin

Question 49

Why can't plants have a small SA:V

Answer 49

they photosynthesise which requires a large SA:V to capture light & exchange gases

Question 50

What adaptations do terrestrial plants have to limit water loss

Answer 50

1) guard cells become flacid so close stomatal pore, limiting water loss 2) waterproof covering

Question 51

What are xerophytes

Answer 51

plants adapted to living in areas with limited water supply

Question 52

What adaptations do xeropytic plants have to limit water loss

Answer 52

1) thick cuticle - shortens pathway 2) curled leaves - stomata inside, protecting them from wind, traps water so increases water potential = minimum conc gradient 3) hairy leaves - trap moist air around stomata, smaller conc gradient 4) stomata in pits - trap moist air increasing conc gradient 5) reduced number of stomata - fewer areas to transpire from

Question 53

What does wind do to the rates of evaporation and diffusion

Answer 53

increases it

Question 54

How much water loss can occur via the cuticle

Answer 54

10%

Question 55

Give and example of a plant with hairy leaves

Answer 55

heather plant

Question 56

Give and example of a plant with sunken stomata

Answer 56

pine trees

Question 57

What other plants have similar adaptations to xeropytes

Answer 57

plants in sand dunes, salt marshes, cold regiona