Exchange Surfaces - Gas Exchange in Other Organisms

Question 1

why do bony fish have a lower metabolism

Answer 1

they are ectotherms

Question 2

why do boney fish have gills

Answer 2

gas exchange

Question 3

why do boney fish have a ventilation system

Answer 3

to maintain a flow of water in one direction over their gills

Question 4

how many pairs of gills do most fish have

Answer 4

four

Question 5

what is the operculum

Answer 5

bony flap that covers and protects gills

Question 6

what does each gill consist of

Answer 6

two rows of many gill filaments attached to a bony gill arch

Question 7

what do the filaments consist of

Answer 7

• the surface of the filaments is folded into many lamellae, giving a very large surface area
• blood capillaries take deoxygenated blood close to the surface of the lamellae where gas exchange occurs

Question 8

how are the gills adapted for efficient gas exchange

Answer 8

• many filaments and lamellae (large surface area for diffusion to take place over
• rich blood supply (maintains a diffusion gradient)
• thin layers (short diffusion pathway)

Question 9

describe the flow of water over the gills and blood in the gill filaments

Answer 9

they flow in opposite directions (counter current flow)

Question 10

why is the counter current flow the most efficient for gas exchange

Answer 10

blood flows across the lamellae in the opposite direction to the movement of water. this maintains a concentration gradient across the whole gill surface so that a maximum volume of oxygen can be absorbed

Question 11

what is the effect of the mouth opening (operculum is closed)

Answer 11

• floor of the buccal cavity is lowered
• volume in the buccal cavity increases, which decreases the pressure compared to the outside
• water moves into the buccal cavity down a pressure gradient
• the opercular cavity expands

Question 12

what is the effect of the mouth closing

Answer 12

• floor of the buccal cavity is gradually raised
• the pressure inside the buccal cavity is now higher than in the opercular cavity pushing water over the gills
• the operculum opens
• the sides of the opercular cavity move inwards, increasing the pressure
• water flows out the fish through the operculum

Question 13

what specific problems with gas exchange may insects face

Answer 13

• active so high demand for oxygen
• tough exoskeleton

Question 14

what is the name of the gas exchange system in insects

Answer 14

tracheal system - delivers oxygen directly to cells
they have many tiny pipes called tracheae

Question 15

how does air enter the tracheae

Answer 15

through spiracles in the thorax and abdomen

Question 16

how and why are the tracheae kept open

Answer 16

by spirals of chitin to allow air to move through them

Question 17

what do the tracheae branch into

Answer 17

many microscopic tubes called tracheoles (approx 0.7 micrometres in diameter)

Question 18

describe tracheoles

Answer 18

fully permeable to gases, so gas exchange takes place between the cells and the tracheoles

Question 19

what enters or leaves the insect via the spiracles

Answer 19

air can enter or leave
water can be lost

Question 20

how can water loss via the spiracles be reduced

Answer 20

hairs around the spiracles

Question 21

how can spiracle sphincters increase efficiency of gas exchange but minimise water loss

Answer 21

they can open or close the spiracles

Question 22

what is the function of tracheal fluid

Answer 22

limits the penetration of air
- during vigorous muscular activity lactic acid builds up in the insect’s tissues
- this causes water to move out of the tracheoles by osmosis
- more air enters the tracheoles increasing the area for gas exchange