Exchange surfaces

Question 1

Why is diffusion enough to supply oxygen for single - celled organisms?

Answer 1

1) Metabolic activity is low (therefore oxygen demand and carbon dioxide production is low)
2) The SA:V is large (so diffusion distances are small)

Question 2

4 features of effective exchange surfaces:

Answer 2

1) Large surface are (usually as a result of a large number of them)
2) Thin layers (short diffusion pathway)
3) Good blood supply (maintains a steep conc gradient for diffusion)
4) Good ventilation (maintain a diffusion gradient)

Question 3

5 key structures involved with the mammal gas exchange system:

Answer 3

1) The Nasal Cavity
2) Trachea
3) Bronchus
4) Bronchioles
5) Alveoli

Question 4

Inspiration

Answer 4

Diaphragm and intercostal muscles contract, rib cage moves upwards and outwards, volume of thorax increases so pressure decreases and air moves in.

Question 5

Expiration

Answer 5

Diaphragm and intercostal muscles relax, rib cage moves downwards and inwards, decrease the volume inside the thorax and increase the pressure.

Question 6

Adaptations of Gills (5)

Answer 6

1) large SA
2) thin layers
3) good blood supply
4) tips of adjacent gill filaments overlap to increase the resistance of the flow of water and slows it down (more time)
5) water movement and blood flow in different directions (countercurrent exchange system)

Question 7

Gas exchange in insects

Answer 7

THEIR EXOSKELETON IS IMPERMEABLE TO GASES:
Spiracle: lets air in and out but like stomata water is lost.
Trachea: lined by spirals of chitin (keeps them open if bent) which is relatively impermeable to gases.
Tracheoles: not lined with chitin, freely permeable and runs in between individual cells

Question 8

Water flow over gills as the mouth opens

Answer 8

1) Mouth opens, floor of the buccal cavity lowers (increases the volume and decreases the pressure so water is drawn in)
2) the opercular valve is closed and the opercular cavity (containing gills) expands, this lowers the pressure so the water moves over the gills as the floor of the buccal cavity rises.

Question 9

Water flow over gills as the mouth closes

Answer 9

1) The opercular valve opens and the sides of the cavity move inwards.

This increases the pressure over the opercular cavity so water is forced over the gills, the floor of the buccal cavity is steadily moved up to maintain the flow of water

Question 10

The nasal cavity(3)

Answer 10

large SA with a good blood supply that warms the air to body temp,

hairy lining to secrete mucus,

moist surfaces to humidify the air and reduce evaporation

Question 11

Trachea(2)

Answer 11

incomplete rings of cartilage,

lined with cilia and goblet cells

Question 12

Bronchus

Answer 12

rings of cartilage

Question 13

Bronchioles(2)

Answer 13

epithelium and smooth muscle

Question 14

alveoli(5)

Answer 14

large number=large SA,

elastic fibres,

good ventilation,

good blood supply,

thin layers