Gas exchange

Question 1

what do most exchange surfaces have in common

Answer 1

large surface area
thin - short diffusion pathway
steep concentration gradient

Question 2

how do single celled organisms exchange gases

Answer 2

through surface

by diffusion

Question 3

why is there no need for a gas exchange system in single celled organisms

Answer 3

they have a relatively large surface area + short diffusion pathway

Question 4

where is there a higher concentration of oxygen

Answer 4

in water than in the fish

Question 5

where does water enter from

Answer 5

the mouth

Question 6

where does water pass out from

Answer 6

the gills

Question 7

what is each gill made of

Answer 7

thin plates

called gill filaments

Question 8

what do gills provide

Answer 8

large surface area

Question 9

what are gill filaments covered in

Answer 9

lamellae

Question 10

what do lamellae do

Answer 10

increase the surface area even more

Question 11

how do lamellae increase rate of diffusion

Answer 11

have lots of blood capillaries

thin surface layer

Question 12

how do blood and water flow

Answer 12

in opposite directions

Question 13

what is a counter - current system

Answer 13

blood and water flowing in opposite directions

Question 14

what does a counter-current system maintain

Answer 14

a concentration gradient

Question 15

how does the counter-current system maintain a concentration gradient

Answer 15

concentration of oxygen in water always higher than in blood
so as much oxygen diffuses into blood from water as possible

Question 16

what are tracheae

Answer 16

air filled pipes

Question 17

what is the function of tracheae

Answer 17

gas exchange

Question 18

how does air move into the trachea

Answer 18

through pores on surface

called spiracles

Question 19

how does oxygen from the air travel to cells in the insect

Answer 19

down the concentration gradient

Question 20

how does the oxygen get to each individual respiring cell

Answer 20

trachea branches into tracheoles
which have thin, permeable walls
and branch off into each cell

Question 21

how does carbon dioxide leave the cells?

Answer 21

down its concentration gradients

through the spiracles

Question 22

how do insects move air in/out the spiracles

Answer 22

through rhythmic abdominal movement

Question 23

what is the main site of exchange in plants

Answer 23

mesophyll cells in leaf

Question 24

how are spongy mesophyll cells adapted for exchange

Answer 24

large surface area

Question 25

through what do gases move in/out the cells

Answer 25

stomata

Question 26

what controls the opening of the stomata

Answer 26

guard cells

Question 27

how would guard cells control the opening of the stomata if too much water is lost

Answer 27

guard cells become flaccid

closing the opening

Question 28

how can insects reduce water oss

Answer 28

close their spiracles using muscles
waterproof waxy cuticle all over body
tiny hairs around spiracles

Question 29

how can plants reduce water loss

Answer 29

guard cells become flaccid

which closes the pore

Question 30

what are xerophytes

Answer 30

plants adapted for life in warm, dry or windy conditions where water loss is a problem

Question 31

what are some xerophytic adaptations

Answer 31

stomata sunk in pits

layer of hairs on epidermis

curled leaves with stomata on inside

reduced number of stomata

waxy, waterproof cuticles on leaves + stem

Question 32

how do sunken stomata reduce water loss

Answer 32

trap moist air -
reducing con gradient of water between leaf + air
- reduces amount of water diffusing

Question 33

how do layers of hair on epidermis reduce water loss

Answer 33

to trap moist air around stomata

reducing con gradient of water between leaf + stomata reduces amount of water diffusing

Question 34

how do curled leaves reduce water loss

Answer 34

protecting stomata from wind

reducing chance of diffusion + evaporation

Question 35

how does a reduced no of stomata reduce water loss

Answer 35

fewer places for water to escape

Question 36

how do waxy, waterproof cuticles reduce water loss

Answer 36

reduce evaporation