3.1.5 gas exchange in other organisms (bony fish & insects)

Question 1

(fish) buccal cavity

Answer 1

mouth

Question 2

(fish) countercurrent flow

Answer 2

2 fluids flow in opposite directions

Question 3

(fish) filaments
—> what’s another name for these

Answer 3

slim branches of tissue that make up the gill
(primary lamellae)

Question 4

(fish) lamellae
—> what can these also be called

Answer 4

folds of filament to increase surface area
—> often called secondary lamellae or gill plates

Question 5

(fish) operculum

Answer 5

bony flap that covers/protects gills

Question 6

(insect) spiracle

Answer 6

external opening/pore that allows air in/out of tracheae

Question 7

(insect) tracheal fluid

Answer 7

fluid found at ends of tracheoles in tracheal system

Question 8

(insect) tracheal system

Answer 8

system of air-filled tubes

Question 9

how do bony fish exchange gases

Answer 9

using gills to absorb oxygen dissolved in water & release carbon dioxide into water

Question 10

how many pairs of gills do most bony fish have

Answer 10

5

Question 11

what does each gill consist of

Answer 11

2 rows of gill filaments attached to bony arch

Question 12

describe the gill filaments

Answer 12

• very thin
• surface folded into many secondary lamellae (gill plates) = large surface area

Question 13

how does exchange occur in bony fish

Answer 13

capillaries carry deoxygenated blood close to surface of secondary lamellae

Question 14

describe the dissection of a fish gill

Answer 14

1. find operculum
2. lift operculum to observe gills/colour
3. cut away one operculum
4. cut out one gill

Question 15

describe the countercurrent flow in bony fish

Answer 15

• blood flows along gill arch & along filaments to secondary lamellae
• then blood flows through capillaries in opposite direction to flow of water over the lamellae

Question 16

what does the countercurrent flow achieve

Answer 16

• maintains high conc. gradient
• absorbs max. amount of oxygen from water

Question 17

describe the process of ventilation in a bony fish

Answer 17

1. fish opens mouth & lowers floor of buccal cavity
2. increases volume & decreases pressure in buccal cavity
3. water’s drawn into mouth
4. mouth closes & floor of buccal cavity is raised
5. decreases volume & increases pressure in buccal cavity
6. water’s pushed from buccal cavity which causes operculum to move outwards = reducses pressure in opercular cavity which helps water flow through the gills

Question 18

what type of circulatory system do insects have & what does that mean

Answer 18

open circulatory system
= body fluid acts as both blood/tissue fluid

Question 19

what do insects possess

Answer 19

air-filled tracheal system = supplies air directly to all respiring tissues

Question 20

how does air enter the tracheal system

Answer 20

via a pore in each segment (spiracle)

Question 21

how is air transported into the body

Answer 21

• through series of tubes called tracheae
• these divide into smaller tubes called tracheoles
• ends of tracheoles are open & filled with fluid (tracheal fluid)

Question 22

where does gaseous exchange occur in an insect

Answer 22

between air in tracheole & tracheole fluid
—> some can occur across thin walls of tracheoles

Question 23

what can happen when insects/the tissues are active

Answer 23

• tracheal fluid can be withdrawn into the body fluid —> increase surface area of tracheole wall exposed to air
  = more oxygen can be absorbed when insect is active

Question 24

how can larger insects also ventilate their tracheal system
- how many ways can this be achieved

Answer 24

movements of the body
—> 3 ways

Question 25

summarise the 3 ways larger insects can ventilate their tracheal system by movements of the body

Answer 25

1. sections of tracheal system are expanded/flexible walls - act as air sacs which can be squeezed by action of flight muscles —> repetitive expansion/contraction = ventilate tracheal system
2. movements of wings alter volume of thorax - thorax vol decreases = air in tracheal system under pressure & pushed out - thorax vol increases = pressure inside drops & air pushed into tracheal system from outside
3. locusts can alter vol of abdomen by specialised breathing movements - coordinated with opening/closing valves in spiracles —> as abdomen expands = spiracles at front of body open & air enters tracheal system —> abdomen reduces in vol = spiracles at rear end open & air can leave tracheal system