2.2 Adaptations for gaseous exchange

Question 1

What must all respiratory surface be? And why

Answer 1

• thin (short diffusion pathway)
• permeable to gases
• moist (allows gases to dissolve)
• large S.A : Vol ratio

Question 2

What are some additional features not present in single celled organisms, insects or plants?

Answer 2

• good blood supply to maintain the conc gradient
• ventilation mechanism to maintain conc gradient

Question 3

As organisms increase in size, what is required? Why?

Answer 3

a specialised gas exchange surface is required to increase the area available

Question 4

Give an example of an unicellular organism, why doesn’t it need a specialised gas exchange surface?

Answer 4

Amoeba
- the S.A is large enough to meet the needs of the organism and therefore the materials can be exchanged directly across its thin and permeable membrane

Question 5

Why is the conc gradient always maintained in unicellular organisms?

Answer 5

bc the cytoplasm is constantly moving

Question 6

Why do larger organisms need a specialised gas exchange surface?

Answer 6

the S.A : Vol ratio decreases so diffusion across body surface doesn’t meed the needs of the organism

Question 7

What is a consequence of maintaining a moist respiratory surface in terrestrial animals? How is this minimised?

Answer 7

water loss, minimised by having internal gas exchange surface: lungs

Question 8

What is the adaptation for gas exchange in a Flatworm?

Answer 8

flattened body to reduce diffusion distance and to increase overall S.A

Question 9

What are the adaptations for gas exchange in a Earthworm?

Answer 9

• secretes mucus to maintain a moist surface
• low metabolic rate to reduce O2 requirements
• network of blood vessels and blood containing haemoglobin for the transport of O2
• CO2 is transported largely in the blood plasma

Question 10

What are the adaptations for gas exchange in Amphibians? eg frogs and newts

Answer 10

• moist and permeable skin w/well developed capillary network beneath the surface
• lungs that are used when more active

Question 11

What are the adaptations for gas exchange in Reptiles? eg snakes

Answer 11

• internal lungs like amphibians, but more complex and larger surface

Question 12

What are the adaptations for gas exchange in Birds?

Answer 12

• flight generates a high metabolic rate and high O2 requirement so birds have efficient ventilation mechanism to increase the conc gradient across the lung surface

Question 13

What are a fish’s specialised gas exchange surface? What else does this mechanism contain?

Answer 13

• gills which have gill filaments, gill rakers ad gill arches and lamellae (gill plates)

Question 14

How do gills have a large S.A?

Answer 14

due to gill filaments

Question 15

Why must water be forced over the gill filaments in aquatic organisms?

Answer 15

water is a dense medium w/low O2 content so water must be forced over the gill filaments

Question 16

What prevents gills from collapsing?

Answer 16

The gill filaments

Question 17

Why do fish die out of water?

Answer 17

b/c the gills collapse and the filaments stick together, reducing the S.A for absorption of O2

Question 18

Why do the gills have an extensive network of capillaries?

Answer 18

to allow efficient diffusion of O2

Question 19

What are the two types of different fish and their different mechanisms?

Answer 19

1. Cartilaginous fish - parallel flow
2. Bony fish - counter-current flow

Question 20

How do cartilaginous fish ventilate their gills?

Answer 20

They swims and open their mouths, allowing H2O to pass over the gills

Question 21

Why is gas exchange only possible over part of the gill filament surface in parallel flow?

Answer 21

As an equilibrium is reached which prevents further diffusion and reduces the oxygen that can be absorbed into the blood

Question 22

Define parallel flow

Answer 22

the blood and water flow in the same direction at the gill lamellae, maintaining the concentration gradient to the point where blood and water concentration is equal.

Question 23

Define counter-current flow

Answer 23

the blood and water flow in opposite directions at the gill lamellae maintaining the concentration gradient along their entire length

Question 24

Why is counter-current flow more efficient?

Answer 24

bc diffusion is maintained along the entire length of the gill filament bc the conc of O2 in H2O is always higher than the blood so eqm is never reached.

Question 25

What are the steps in the ventillation mechanism in bony fish? (water intake)

Answer 25

1. mouth opens 2. floor of buccal cavity lowers 3. opercular valve closes 4. volume increase so pressure decreases

Question 26

What are the steps in the ventillation mechanism in bony fish? (water expulsion)

Answer 26

1. mouth closes 2. floor of buccal cavity rises 3. opercular valve opens 4. volume decreases so pressure increases

Question 27

what do insects have to reduce water loss? how does this work?

Answer 27

exoskeleton made of chitin covered in wax it is impermeable to water and gases

Question 28

starting from the top of the body to the bottom, what are the parts of an insect, what do they have along the body to take in oxygen?

Answer 28

Head Thorax Abdomen Spiracles

Question 29

what do spiracles do?

Answer 29

lead into a system of branched chitin lined airtubes called tracheae tracheole tubes come into direct contact w/every tissue, supplying O2 and removing CO2 so no need for haemoglobin - very rapid

Question 30

what is the purpose of chitin in the tracheal system?

Answer 30

arranged into rings which allow tracheae to expand and contract and act like bellows drawing air in and out of the insects body

Question 31

what do the spiracles act as?

Answer 31

valves, can open and close

Question 32

what is at the end of the tracheae tubes? what is its purpose?

Answer 32

end of tubes are filled with fluid to allow gases to dissolve

Question 33

how do these fluid-filled tubes work?

Answer 33

fluid levels in tracheoles decrease during flight, providing more SA for gas exchange and reducing diffusing distance to make exchange quicker

Question 34

what is the process of gas exchange in insects? (intake of O2)

Answer 34

when abdomen is expanded, thorax spiracles are open and the abdominal spiracles are closed, air enters through thorax spiracles

Question 35

what is the process of gas exchange in insects? (expel of CO2)

Answer 35

as abdomen is compress, thorax spiracles are closed and abdominal spiracles are open, air leaves tracheal system via abdominal spiracles

Question 36

what do muscle fibres connected to tracheoles never exceed? how is this an advantage?

Answer 36

20μm in diameter, provides short diffusion path for gaseous exchange

Question 37

what are the component of the human respiratory system?

Answer 37

larynx trachea rib pleural membranes bronchioles lungs intercostal muscles chest cavity/thorax diaphragm

Question 38

what is the name for the human ventilation mechanism?

Answer 38

Negative pressure breathing

Question 39

Describe what happens during inspiration, active or passive?

Answer 39

active 1. external intercostal muscles contract moving ribs up and out, which pulls outer plural membrane outwards 2. diaphragm contracts and flattens 3. press decreases in pleural cavity and inner pleural membrane moves out 4. this pulls on surface of lungs, causing alevoli to expand 5. alveolar press decreases to below atmospheric press, so air drawn in

Question 40

describe what happens during expiration, passive or active?

Answer 40

passive 1. external intercostal muscles relax, so ribs move down and in, allowing outer pleural membrane to move inwards 2. diaphragm relaxes and moves upwards 3. press increases in pleural cavity and inner pleural membrane moves in 4. pushes on lung surface and causes alveoli to contract 5. alveolar press increases to above atmospheric press and air forced out

Question 41

what are the alveolar adaptations for gas exchange?

Answer 41

very large SA:VOL ratio very thin walls surrounded by capillaries so short diffusion distance and good blood supply moist lining for gases to dissolve collagen and elastic fibres allow expansion and recoil oxy blood carried away from alveolus and blood rich in CO2 returns

Question 42

what do alveoli produce and why is this beneficial?

Answer 42

produce surfactant lowers surface tension to prevent alveoli from collapsing and sticking together and allowing gases to dissolve

Question 43

what is the last thing to develop in the foetus and why are babies given it?

Answer 43

surfactant to prevent alveoli in their premature lungs from sticking together

Question 44

why is there a higher percentage of oxygen gas in inspired air vs expired in the alveoli?

Answer 44

O2 is absorbed into red blood cells at alveoli and used in aerobic resp

Question 45

why is there a low percentage of CO2 gas in inspired air vs expired in the alveoli?

Answer 45

CO2 produced by resp diffuses from blood plasma into alveoli

Question 46

why is there a same percentage of oxygen gas in inspired air vs expired in the alveoli?

Answer 46

N2 is neither absorbed nor used so all inhaled is exhaled

Question 47

how do you calculate percentage of oxygen extracted? use these figures: inhaled = 20% exhaled = 16%

Answer 47

%O2 extracted = %O2 absorbed/% of air that is O2 x100 = 4/20x100 = 20%

Question 48

how do plants reduce H2O loss?

Answer 48

waxy cuticle layer

Question 49

what is the function of the upper epidermis?

Answer 49

transparent cells which allow light to pass to mesophyll tissue, also synthesises and secrete waxy cuticle

Question 50

what is the function of the palisade mesophyll?

Answer 50

contain many chloroplasts for photosynthesis, main photosynthetic tissue

Question 51

what is the function of the spongy mesophyll

Answer 51

also carry out photosynthesis, air spaces allow for circulation of gases

Question 52

what is the function of the vascular bundles?

Answer 52

xylem - H2O and mineral transport phloem - transport of photosynthetic products

Question 53

what is the function of the guard cells?

Answer 53

become turgid and flaccid due to change in H2O potential, opens and closes stomatal pore

Question 54

what is the function of the stomata?

Answer 54

allow gaseous exchange to occur

Question 55

what are the leafs' adaptations for photosynthesis?

Answer 55

large SA to capture as much light as possible thin to allow light to penetrate lower cell layers cuticle and epidermis are transparent to allow light to penetrate mesophyll palisade cells packed w/chloroplasts

Question 56

what are the two structures which allow reactants to reach the palisade mesophyll cells?

Answer 56

xylem and stomata

Question 57

what are the two structures that allow products to be moved from palisade mesophyll cells?

Answer 57

stomata or phloem

Question 58

describe the stomata opening mechanism

Answer 58

guard cells photosynthesise, producing ATP energy released from ATP is used to actively transport k+ ions into guard cells this triggers starch (insoluble) to be converted to malate ions (soluble) H2O potential of guard cells is lowered so water enters cells by osmosis guard cells expand and outerwall stretches more than the inner wall bc it's thinner, creating a pore

Question 59

describe the stomatal closing mechanism

Answer 59

light intensity too low for photosynthesis, k+ diffuse down conc grad out of guard cells malate converted back to starch by condensation reaction H2O potential of guard cells increased as water potential of cells less negative water leaves by osmosis guard cells become flaccid, stomatal pore closes preventing gas exchange and reducing water loss