Gas exchange

Question 1

As size of an organism increases what happens to its surface area to volume ratio?

Answer 1

It decreases

Question 2

Describe and explain the five common features of gas exchange surfaces

Answer 2

Many folds to increase surface area, thin to give short diffusion distance, permeable so gases can pass through, moist so gases can dissolve, a ventilation mechanism/good blood supply to maintain concentration gradient

Question 3

Name the gas exchange surface of a fish

Answer 3

Gill plates (or lamellae)

Question 4

Name the gas exchange surface of an insect

Answer 4

Tracheoles

Question 5

Name the gas exchange surface of a mammal

Answer 5

Alveoli

Question 6

Name the gas exchange surface of an amphibian

Answer 6

Alveoli/skin surface for a frog depending on activity level

Question 7

Give the advantages of an insect gas exchange system

Answer 7

Oxygen diffuses directly to cells, no need to produce haemoglobin, spiracles can be closed to reduce water loss, Hairs in
spiracles to trap moisture

Question 8

Give the disadvantages of an insect gas exchange system

Answer 8

Rate of diffusion limits size and shape of insect, mass of chitin could make it difficult to fly

Question 9

Why is it difficult to extract oxygen from water?

Answer 9

It is dense, viscous and has a low oxygen concentration

Question 10

Give the advantage of countercurrent flow in fish gills

Answer 10

Maintains concentration gradient across entire gill plate/doesn’t reach equilibrium

Question 11

Why can’t fish survive out of water?

Answer 11

Gill plates stick together due to surface tension, decreasing surface area and increasing diffusion distance for gas exchange.

Question 12

How do fish breathe in?

Answer 12

They open the mouth, close the operculum and lower the floor of the mouth cavity. This increases the volume and decreases pressure.

Question 13

How do fish breathe out?

Answer 13

They close the mouth, open the operculum and raise the floor of the mouth cavity. This decreases volume, increases pressure and pushes water past the gills

Question 14

Why do terrestrial animals have internal lungs?

Answer 14

To minimise heat and water loss

Question 15

Which cells secrete mucus?

Answer 15

Goblet cells

Question 16

What is the function of ciliated epithelium in the trachea and bronchi?

Answer 16

To waft mucus which contains bacteria up to the back of the throat where it can be swallowed

Question 17

What is the function of the elastic fibres in the alveoli?

Answer 17

To stretch and recoil

Question 18

What is the function of the cartilage in the trachea?

Answer 18

To prevent the trachea from collapsing during inspiration

Question 19

Why is the cartilage in the trachea a C shaped ring rather than a circle?

Answer 19

To allow the oesophagus to expand when swallowing

Question 20

What is the function of surfactant?

Answer 20

Reduces surface tension to prevent alveoli sticking together when breathing out

Question 21

Which membranes surround the lungs?

Answer 21

Pleural membranes

Question 22

How do the ribs and diaphragm cause inhalation?

Answer 22

Diaphragm contracts and lowers, external intercostal muscles contract to raise the ribcage. Volume of alveoli increases, pressure decreases below atmospheric. Air is drawn in

Question 23

How are the pleural membranes involved in forced inhalation?

Answer 23

External intercostal muscles raising the ribcage pulls out the outer pleural membrane, reduces pressure in the pleural cavity and the inner pleural membrane moves outward. This pulls on the surface of the lungs and causes the alveoli to expand. Volume of alveoli increases, pressure decreases below atmospheric. Air is drawn in

Question 24

How do humans exhale?

Answer 24

Diaphragm relaxes and moves up into dome shape, external intercostal muscles relax and ribcage lowers. Volume decreases pressure increases.