Biology Mark scheme flashcards > Gas exchange > Flashcards

Gas exchange Flashcards

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1
Q

State two important structural features of alveoli (2)

A
  • one cell thick
  • large surface area
  • large number of capillaries
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2
Q

Briefly explain how inspiration is brought about (2)

A
  • contraction of intercostal muscles and diaphragm
  • increased volume and decreased pressure so air moves into lungs
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3
Q

Describe three features of fish gills allow them to acheive efficient gas exchange (3)

A
  • large surface area
  • thin - short diffusion pathway
  • permeable
  • good blood supply
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4
Q

Water is a dense medium with a low oxygen content. Explain how bony fish overcome problems of oxygen uptake in water (4)

A
  • water forced over fill by pressure differences
  • one way flow
  • counter current flow of blood and water
  • concentration gradient maintained over entire gill surface
  • high affinity of haemoglobin
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5
Q

Explain why large mult cellular organims have evolved special surfaces for gas exchange (3) descibe and explain how terrestrial animals are adapted for gas exchange (7)

A
  • metabolic needs are larger organisms need more oxygen
  • external surface insufficient for gas exchange
  • diffusion proportional to surface area
  • SA:V is to small
  • diffusion distances are large
  • not enough O2 can diffuse
  • large number of alveolus increase surface area
  • reduce heat loss/ water loss
  • internal lungs
  • gas exchange take place in alveoli
  • thin walls - short diffusion pathway
  • moisture allow gases to dissolve
  • blood capillaries maintain concentration gradient between air and body
  • heamoglobin transsport of oxygen
  • replace stale air with fresh air
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6
Q

Describe and explain the process of inspiration in a mammal (4)

A
  • intercostal muscles contract and ribs move up and out
  • diaphragm contract and diaphragm flattens
  • internal volume of thorax increases
  • pressure in lungs decreases
  • higher air pressure outside forces air into lunds
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7
Q

Explain how counter current flow works in gills of bony fish (4)

A
  • blood flows across gills in opposite direction to water
  • water always has more oxygen than blood
  • oxygen passes from water into blood
  • across entire gill
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8
Q

Explain why parallel flow is less effeicient than counter current flow (2)

A
  • equilibrium is reached part way across gill
  • less oxygen uptake
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9
Q

Suggest why gill filaments would not provide an effient gas exchange surface on land (2)

A
  • gills dry out prevents oxygen from dissolving on surface of skin
  • fills may collapse decrease of surface area
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10
Q

Describe three properites that all respiratory surfaces musst possess and why (3)

A
  • thin - short diffusion pathway
  • large surface area - for gas exchange
  • moist - allow gases to dissolve
  • permeable - allow gases to pass through
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11
Q

Give two reasons why gilld do not function effectivley on land (2)

A
  • they dry out
  • they clump together and collapse
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12
Q

Define counter current flow as seen in gilld of bony fish and explain why counter current flow is more efficient (3)

A
  • blood flows in opposite direction to water
  • concentration gradient is maintained across whole urface
  • greater concentration of oxygen in blood is achieved
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13
Q

Bony fish relies on gills for gas exchange explain how the prescenece of gill filaments is an adpatation to gas exchange (2)

A
  • increase surface area
  • diffusion takes place
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14
Q

Describe the process of ventilation in bony fish (4)

A
  • buccal cavity lowered
  • volume buccal cavity increases pressure decreases
  • water pulled in from outside
  • mouth closes and buccal cavity raises
  • water forced into gills
  • pressure in gill cavity increases
  • forces open operculum
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15
Q

Suggest why muscle fibres do not exceed a large diameter (2)

A
  • diffusion pathway would be to lond
  • speed up diffusion
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16
Q

Describe the change in fluid level in tracheoles during flight and suggest how this changes benefits of gas exchnange during flight (2)

A
  • less fluid
  • more area for gas exchange
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17
Q

Suggest how marram grass is adapted with it’s distribution of stomata to conserve water (3)

A
  • less stomata
  • rolles upper epidermiss face inwards
  • no stamate on lower surface
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18
Q

Give two structural adaptation shown by marram grass help it to survive in dry conditions (2)

A
  • waxy cuticle on lower surface
  • reduced leaf surface area
  • sunken stomata
  • hairs
  • long roots
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19
Q

Describe how bony fish ventialtes it gills and absorbs oxygen from water

A
  • water forced over gill
  • by pressure changes
  • action of mouth and operculum
  • water flows in opposite direction to blood/counter current flow
  • maintains concentration gradient across whole gill
  • as blood always meet water with high oxygen concentration
  • equilibrium is never reached
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20
Q

Describe four similiarities in the adaptations of gill for gas exchange and mamalian villi for absorption of digested products (4)

A
  • large surface area
  • large network of capillaries
  • thin
  • moist
  • short diffusion pathway
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21
Q

Describe how the gills of both bony fish and axolotl are adapted to increase efficiency of gas exchange and explain how structures in heads of bony fish enable them to be highly active even why oxygen levels are relativley low but axolytuls are slower moving under these conditions (9)

A
  • large surface area due prescence of gill filaments
  • permeable
  • rich blood supply to maintain concentration gradient
  • reduce diffusion distance
  • seperate buccal and opercular cavities
  • opercular close gill cavity
  • lower floor buccal cavity increases volume and decreases pressure in buccal cavity
  • mouth opens and water enters
  • mouth closes floor of buccal cavity is raised
  • increases pressure forces water over gils
  • counter current flow
  • maintain concentration gradient for oxygen across whole gill surface
  • oxygen absorption more effiecient
  • axolotls have external gills so no ventilation mechanism
  • paralllel flow
  • less effiecient as oxygen absorbtion needed for aerobic respiration
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22
Q

Define the term diffusion (1)

A
  • the movement of molecules from a higher to lower concentration
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23
Q

Explain why simple diffusion is adequate in flatworms (2)

A
  • long flattened shape large surface area to volume ration
  • very short diffusion pathway
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24
Q

State where gas exchange occurs in earthworm (1)

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A

body surface/skin

25
Lugworms have external gills how do structural adaptations of lugworms enable to gorw to such a large size (4)
* external gills provide large surface area * increases rate of diffusion * capillaries in body wall provide short diffusion pathway to oxygen * blood vessels transport oxygen to all parts of the body
26
Describe and explain common adaptations of gas exchange surfaces found in fish and mammalss (3)
* thin - reduce diffusion distance * moist - gases to dissolve * rick blood supply - maintain concentration gradient * large numbers - large surface area
27
Suggest why warm blooded animals have a constant body temperature and have a higher metabolic rate (2)
* body temperature no dependent on environment * energy needed to generate heat * provide optimum teperature for enzymes
28
Explain the advantage of inset closing spiracles (1)
reduce water loss
29
Suggest a role of air sac in insects (1)
* provide a resovoir of air when spiracles closed
30
Explain the advantag to insect having a ventilation system (1)
* maintain a concentration gradient
31
The chitin of the walls of the trachea have a similar chemical bonding and function as cellulose in plant cell wallss enable it to carry out it function in insects (3)
* alternate monosaccharidess rotated by 180 * cross linking between molecules forming microfibrils * providing strength
32
Describe how adaptations including outer body surface is folded , head buried in mud when highly acitve, art of body expossed to water move vigorulsy red in colour due to haemoglobin enavle worms to survive in water with very low oxygen levels (9)
* skin is gas exchang surface * folded outer body surfaces further increases surface area for diffusion * diameter is narrow short diffusion pathway * cyclindrical - large surface area to volume ratio * head buried in mud so more ssurface in contact with gas exchange medium * part of body exposed to water maintain steep concentration gradient * prescence of haemoglobin inceases ability to absorb oxygen * presecence of blood vessels transport oxygen / maintain diffusion gradient * haemoglobin hgih affinity ffor oxygen
33
Describe the process of inspiration in a mammal (4)
* intercostal muscles contract and ribs move up and out * diaprahgn muscles contract and diaphragm flattens * internal volume of thorax increases * pressure in lungs decreases * air pressure is higher outide drawing air into the lungs
34
Explain how counter current flow works in the gills of bony fish (4)
* blood flows across gills in opposite direction to water * water always has more oxygen than blood * diffusion gradient maintained * oxygen passes from water into blood * across entire gill surface * more oxygen is taken up
35
Explain why parallel flow is less effient than counter current flow (2)
* equilibrium is reacher * less oxygen uptake
35
Suggest why gill fillaments would not provide an efficient gas exchange surface on land (2)
* gills dry out - prevent oxygen dissolving on surface of gills * gills may collapse - decreae in surface area
35
Explain how the prescence of gill filaments is an adaptation to gaseous exchange (2)
* increase surface area * diffuion takes place
36
Describe the process of ventialtion in a bony fish (4)
* mouth opens/ buccal cavity is lowered * volume of buccal cavity is increases/pressure decrease * water pulled in from outside * mouth closes and buccal cavity raises * water forced through fills * pressure in gill cavity increase * forces open the operculum
37
State what is meant by counter current flow and how this increases the efficieny of gas exchange in the bony fish (3)
* blood flows across gill filaments in opposite directions to water * blood always meets water containing a higher concentration gradient / diffusion gradient maintained * equilibrium is never reached * across entire gill * higher satruation of blood with oxygen achieved
38
Suggest why the diameter of the mucle fibre in insects do not exceeed 20 micrometres (2)
* diffuion pathway would be too long * speed of diffusion would be to low * to supply sufficient oxygen
39
Describe the change of fluid level in the tracheoles of an insect during flight and it benefits for gas exchange (2)
* less fluid * more area for gas exchange/ short diffusion pathway
40
Describe how bony fish ventilate the gills and absorbs oxygen from water (4)
* water forced over gill * by pressure changes * action of mouth and operculum * water flows in opposite direction to blood - counter current * maintains diffussion graident along entire gill * a blood alwaus meet water with a higher oxygen concentration equilbrium is never reached
41
Describe four similarities in the adaptation of the fill for gaseous exchange and a mammalian villu for the absorption of digested products (4)
* large surface area * dense network of capillaries * thin / permable epithelium * moist * short diffuion pathway
42
State two important features of the alveoli (2)
* thin / one cell thick * large surfce area / highly folded * large number of capillaries
43
Brifly explain how inspiration i bought around (2)
* contraction of the intercostal muscles and the diaphragm * increased volume and decreased pressure so air moves into lungs
44
Describe the process of expiration in a mammal (4)
* intercostal mucles relax alllowing the ribcage to move downwards and inwards * the diaphragm muscles relaxes and becomes dome haped * decreases the volume of the thorax * which increaes the pressure in the lungs * forcing air out of the lungs
45
Suggest why they need a complex ventilation meachanism (2)
* high metabolic rates * ventialtion mechanisms maintains a steep concentration gradient / suffiecient oxygen supplied to alveoli
45
Give two advantages of humans having internal gas exchange surfaces (1)
reduce heat and water loss
45
Explain how the outward movement of the ribcage causes the changes in playeral and alveolar pressures during breathing in (4)
* intercostal muscles contract * pleural membranes are pulled out * pleural pressure reduced * pleural membrane pulls on lungs and expand alveolu * alveolar pressure lowers * air moved in when alveolar pressure is lower than atomspheric pressure
45
State one medical use of arrtificial surfactant and explain why it would be needed (2)
* premature babies / lung transplants/respiratory distress syndrome * lower surface tenion of the fluid in the alveoli/prevent alveoli from collapsing
45
Describe three features of gills allow them to acheive efficient gas exchange (3)
* large surface area * thin / short diffusion pathway * permeable * good blood supply
46
Explain how bony fish overcome the problems of oxygen uptake in water (4)
* water forced over the gill by continuous swimming / pressure differences * one way flow * counter current flow of blood and water * concentration gradiet is maintained * over entire gill surface * high affinity of haemoglobin
46
Suggest the function of gill rakers (1)
* filter particles * preventing damage to the gill filaments
46
Explain why fish suffocate when out of water (4)
* gills dry out * gills stick together / collapse * reduce surface area for diffusion * water needed for diffuion of gases
46
Explain the advantages of the countercurrent flow mechanism compare dto the parallel flow mechanism (4)
* counter current is more efficient * maintains concentration graient * across entire gill * more oxygen absorbed
46
What is the function of the ciliated epithelial layer in the trachea (2)
* move mucus and bacteria upwards
46
What is the function of the layer of cartilage in the trachea (2)
* prevent trachea closing * during inspiration
46
Suggest why the cartilage is not in the form of a complete ring in the trachea (1)
allow room for the oesophagus to expand when swallowing food
46
Describe 3 adaptations of alveoli that make it a good gas exchange system (6)
* large surface area - increase area over which diffusion can occur * thin walls - short diffustion path * extensive capillary network - maintain diffuion gradient
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