2.2 adaptations for gas exchange

Question 1

4 features of a gas exchange system

Answer 1

• Large sa-vol ratio
  -short diffusion distance
  -permeable
  -mechanism to produce a steep diffusion gradient

Question 2

Gas exchange in cartilaginous fish

Answer 2

-parallel flow
-eq reached
-must swim continuously
-50% efficient
-unable to diffuse across entire gas exchange surface

Question 3

Describe the graph for parallel flow

Answer 3

-as distance along gill lamellae increases, conc of 02 in blood goes up and conc of 02 in water goes down until they are equal

Question 4

What makes bony fish different?

Answer 4

Fish have an operculum, this covers the gills
Bony fish have a ventilation mechanism

Question 5

Describe the stages of the ventilation mechanism.

Answer 5

1. mouth opens = operculum closes
2. buccal cavity floor lowers
   3.vol> … pressure<
3. pressure inside is less than outside so water moves into the mouth.
4. mouth closes = operculum opens
5. buccal cavity floor raises so pressure inside mouth cavity is greater than operculum
6. water moves into the operculum

Question 6

3 features of the gills

Answer 6

-specialised respiratory surface
-large sa due to gill filaments and lamellae
-extensive network of capillaries.

Question 7

Describe counter-current flow

Answer 7

Water moves in opposite direction to the blood inside gill lamellae.
- maintaining the STEEP conc gradient = ensuring eqm is never reached.
- able to diffuse across entire length

Question 8

Describe the process of mammalian ventilation.

Answer 8

• external icm contract
  -ribs up and out
  -diaphragm flattens and contracts
  -outer pleural membrane pulled out with the ribs
  -lungs expand = vol inside alveoli increase
  -atmospheric pressure greater than in the lungs so air is forced into the lungs.

Question 9

Adaptations of the alveoli

Answer 9

-lined in surfactant to prevent collapsing
-1 epithelial cell thick {squamous}
-permeable
-capillary network maintains conc gradient
-large surface area

Question 10

% of oxygen, carbon and nitrogen in the air

Answer 10

20 = O
0.04= CO2
79= N

Question 11

Describe the gas exchange system in insects

Answer 11

-Spiracles open
-air travels down trachea
-branches off into tracheoles
- extends directly into muscle fibres

Question 12

Adaptations of reducing water loss in insects

Answer 12

• spiracles open and close to reduce water loss
  -chittin lined exoskeleton
  -small sa to vol ratio

Question 13

Advantages + disadvantages of insects for gas exchange

Answer 13

• direct diffusion of O2 into muscles, no respiratory pigment needed
• cannot travel fare distances, limits size of insects
  -very efficient

Question 14

Structure of the leaf

Answer 14

waxy cuticle
upper epidermis and lower
palisade mesophyll
spongy mesophyll
stomata = guard cells

Question 15

role of waxy cuticle

Answer 15

reduce water loss

Question 16

role of upper and lower epidermis

Answer 16

transparent to allow light through

Question 17

role of palisade mesophyll

Answer 17

where photosynthesis occurs in leaf

Question 18

role of spongy mesophyll

Answer 18

contains most of the gasses ,allows o2 and co2 to diffuse through

Question 19

How is the conc gradient maintained in the leaf?

Answer 19

Mitochondria respire and produce 02
chloroplast photosynthesise and produce CO2

Question 20

role and location of stomata

Answer 20

-opens and closes due to movement of the guard cell.
-bottom surface of the leaf
-open in sunlight and close at night

Question 21

Stages of stomatal opening

Answer 21

• chloroplast in guard cells photosynthesise and produce ATP
  -ATP provides energy for the active transport of potassium ions into the guard cell.
  -starch is also converted to malate ions
  -this lowers the water potential in the guard cell, so water moves in by osmosis.
  -the guard cells become turgid and swell.
• unevenly thick walls create a pore.

Question 22

What to large organisms need for gas exchange?

Answer 22

-ventalation mechanism
- internal transport system
- respiratory pigment

Question 23

What problems do terrestrial animals face with gas exchange?

Answer 23

• dehydration, water evaporates from body
• gas exchange surfaces are always moist and likely to lose water