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A-level Biology > Adaptations For Gas Exchange > Flashcards

Adaptations For Gas Exchange Flashcards

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1
Q

Define gas exchange

A

The movement of gases between an organism and it’s environment

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2
Q

Define metabolism

A

The total chemical processes in the body

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3
Q

Define respiratory surface

A

The site of gas exchange

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4
Q

Define terrestrial

A

Lives on land

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5
Q

Define amoeba

A

A water living organism in which gas diffusion occurs over its membrane

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6
Q

Define operculum

A

Gill cover

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7
Q

Define counter current

A

Flowing in opposite directions

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8
Q

Define stomata

A

Pore, located on the lower side of leaf through which gases diffuse

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9
Q

What is gas exchange?

A

The movement of gas down a concentration gradient

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10
Q

What is the formula for ficks law for rate if diffusion?

A

Rate of diffusion= (sa X conc gradient) / diffusion distance

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11
Q

Define ventilation

A

Bringing gases to or from a gas exchange surface. Only in some organisms

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12
Q

Define respiration

A

Metabolic pathway that releases chemical energy from food molecules Happens in all organisms.

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13
Q

Give an example of a unicellular organism

A

Amoeba (protoctistan)

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14
Q

What are the features of a unicellular organism that aids has exchange

A
  • large sa:vol ratio
  • thin cell membrane for rapid diffusion
  • small diffusion distances
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15
Q

What must a respiratory surface have for rapid diffusion of gases?

A
  • large sa
  • thin for short diffusion pathway
  • permeable
  • mechanism for steep diffusion gradient across respiratory surface
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16
Q

What do the features of a unicellular organism aid for gas exchange?

A
  • absorb enough oxygen to meet needs required for respiration
  • remove co2 quickly enough to prevent building up a higher concentration and making the cytoplasm too acidic to function
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17
Q

Give some characteristics of a unicellular organism (amoeba)

A 
Nucleus 
Cell membrane
Cytoplasm
Contractive vacuole 
Lives in fresh water as if on land, it will dehydrate and die
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18
Q

What happens to the sa:vol ratio as the size of an organism increases?

A

The sa: vol ratio decreases as size gets bigger for similar overall shape of organism

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19
Q

How does a flatworm achieve a large ss:vol ratio and a short diffusion distance?

A

Flat body so no body part is far away from the surface/skin

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20
Q

Why is a flatworm being aquatic significant?

A

It doesn’t get dehydrated so won’t dry out and die because it’s skin is very permeable.
It is constantly respiring

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21
Q

Does an earthworm have lungs?

A

No. They absorb o2 through their skin

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22
Q

What is the respiratory surface of an earthworm?

A

The skin

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23
Q

Why does the earthworm have a low oxygen requirement?

A

Slow moving with a low metabolic rate. Enough oxygen can diffuse through the permeable skin to the capillaries

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24
Q

Why does the earthworm have a circulatory system?

A

So oxygen can be carried away from the skin/surface to maintain a diffusion gradient and carbon dioxide can diffuse out down the concentration gradient.

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25
Q

How does the earthworm have short diffusion distances?

A

The capillaries are close to the surface

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26
Q

How is a large concentration gradient maintained in an earthworm?

A

Haemoglobin in blood carries the oxygen around the body in the blood vessels and carries oxygen away from the skin.

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27
Q

Why is it important the amphibians have internal lungs?

A

So when they are active they can get more oxygen than through their skin alone to minimalism the loss of heat and water too.

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28
Q

Why are tadpoles able to have external gills?

A

Because they stay in the water

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29
Q

What is the gas exchange surface of an amphibian when it is a)resting b)active?

A

Skin

Lungs

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30
Q

What is the importance of a well developed capillary network beneath the skin of the frog?

A

Maintain concentration gradient to absorb oxygen through the skin and reaches cells

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31
Q

What are the disadvantages to a frog having thin and permeable skin?

A

Water evaporates from the body surfaces and this could result in dehydration

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32
Q

How do the lungs of amphibians differ from those of reptiles?

A

Reptiles have more complex structures increasing surface area for gas exchange

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33
Q

What do Burke’s need a high volume of oxygen intake?

A

Because flight requires much energy. This means more oxygen must be consumed for use during respiration.

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34
Q

How do birds ventilate their lungs without a diaphragm?

A

Ribs and flight muscles.

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35
Q

Why do fish need a good supply of oxygen?

A

Because they are always active

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36
Q

What is the gas exchange surface of a fish?

A

The gills

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37
Q

How does gas exchange occur across the gill?

A
  • one way current of water in a continuous flow
  • folds provide a large surface area which the water flows and gases are exchanged.
  • large surface area maintained as density of water flowing through prevents gills collapsing
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38
Q

What are the two types of fish? Give examples.

A

Cartilaginous fish have skeletons made of cartilage (sharks)

Boney fish have skeletons made of bones (cod)

They ventilate their gills in different ways.

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39
Q

Describe the characteristics of boney fish

A
  • internal skeleton of bone
  • gills covered by a flap called the operculum
  • live in fresh water and sea water
  • most numerous of aquatic vertebrates
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40
Q

What is the structure of fish gills?

A

Gill arch
90’ to arch is the filaments
On the filaments there are lamellae.

There are four gill arches on each side

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41
Q

Can equilibrium be reached during counter current flow?

A

No

42
Q

What is the operculum?

A

The covering over the gills of a bony fish

43
Q

What is counter current flow?

A

Blood and water flow in opposite directions at the gill lamellae maintaining the concentration gradient therefore oxygen diffusion into the blood along the entire length

44
Q

How does water flow to provide counter current flow?

A

Water moves into the mouth cavity to the operculum mar cavity into the Gill pouches where it flows in the opposite direction to the blood in the gill lamellae

45
Q

Why will counter current flow never reach equilibrium?

A

The higher the distance across the lamellae the higher the concentration of oxygen in the blood capillaries and oxygen in water decreases. Water will always have more oxygen in it than the blood.

46
Q

Why is it important for fish to have very good oxygen extraction?

A

Much less diffused oxygen in the water than in air

47
Q

What is more efficient: parallel flow or counter current flow? Why?

A

Counter current flow because equilibrium is never reached.

48
Q

Describe the ventilation of bony fish.

A
  • maintains a continuous one direction flow of water.
  • pressure in the mouth cavity is higher than the operculum cavity
  • operculum acts as a valve to let water in and out as a pump to mover water past the gill filaments
49
Q

Describe inspiration of a bony fish (taking in water)

A
  • mouth opens
  • operculum closes
  • floor of mouth lowers
  • volume of mouth cavity increases
  • pressure inside cavity decreases
  • water flows in as he external pressure is higher than inside the mouth.
50
Q

Describe expiration of a bony fish(forcing water out.)

A 
Mouth closes
Operculum opens
Floor of mouth raises
Volume inside mouth cavity decreases
Pressure inside cavity increases
Water flows out over the gills because the pressure in the mouth cavity is higher than the operculum cavity and outside.
51
Q

Describe carbon dioxide exchange in the gills for cartilaginous fish

A

Co2 diffuses from the blood into the water in cartilaginous fish

52
Q

Describe co2 gas exchange in the gills for bony fish.

A

Counter current system co2 diffuses our if the blood along the lamellae

53
Q

What are the characteristics of the gills?

A
  • Specialised respiratory surface rather than the whole body
  • large surface area enlarged by gill filaments and lamellae
  • extensive network of capillaries with blood carrying haemoglobin for efficient diffusion if co2.
54
Q

Give some characteristics of a cartilaginous fish.

A
  • skeletons made entirely of cartilage
  • most commonly live in the sea
  • 5 gill clefts open at five gill slits
  • no operculum
  • gas exchange occurs during parallel flow of blood and water
55
Q

Why is parallel flow relatively inefficient?

A

Diffusion gradient isn’t maintained.

56
Q

Describe gas exchange during parallel flow

A
  • blood in capillaries flows in the same direction as water
  • begins with rapid diffusion as there is a steep concentration gradient as h2o has much more oxygen than blood
  • oxygen diffuses from water to blood until equilibrium has been reached.
  • further along the lamella, the lower the concentration gradient.
57
Q

How do sharks ventilate their gills?

A

They have to swim constantly with their mouth open to force water and oxygen through their gills.

58
Q

Why is sharks blood only limited to 50% oxygen saturation?

A

Because oxygen will diffuse from water to blood down the concentration gradient until an equilibrium has been reached because the blood and the water are flowing in the same direction.

59
Q

Why does gas exchange only occur over part of the lamella?

A

Because at some point, equilibrium will be reached.

60
Q

How do insects reduce water loss?

A
  • waxy coating
  • waterproof
  • exoskeleton which is rigid with a thin waxy layer and thinner layer of chitin and protein
61
Q

Why do insects need to restrict water loss from their bodies?

A

Because they are terrestrial so will easily become dehydrated as water evaporates from their body

62
Q

What is an insects sa:vol ratio like?

A

Relatively small

63
Q

Why don’t insects use their body surface as a gas exchange surface?

A
  • the exoskeleton is impermeable

- small sa:volume ratio

64
Q

What is the gas exchange surface of an insect?

A

Spiracles

65
Q

What is the ventilation system of an insect like?

A

Paired holes called spiracles in the side of the abdomen run along the side of the body.
Spiracles lead to a system of branched, chitin lined air tubes called tracheae which branch off into smaller tubes called tracheoles.

66
Q

How do spiracles prevent water loss?

A
  • They open and close

- hairs covering the spiracle contribute by preventing solid particles getting in.

67
Q

When insects are resting what do they rely on for gas exchange?

A

Diffusion through the spiracles, tracheae and tracheoles to take oxygen in and remove carbon dioxide.

68
Q

What do insects do during periods of activity to ventilate the tracheae?

A

Movements of the abdomen ventilate the tracheae.

69
Q

Why is no respiratory pigment or blood circulation needed in insects?

A

The ends of the tracheoles are fluid filled. And close to muscle fibres. Oxygen will dissolve into the fluid and diffuse directly into muscle cells.

Carbon dioxide diffuses out by the reverse process.

70
Q

How do larger insects ventilate when active?

A

Water moved from tips if tracheoles by osmosis into the muscles. This is because lactic acid is produced which lowers the water potential meaning water moves into the muscles there by providing them with oxygen.

71
Q

How is oxygen rapidly gained by ventilation in insects?

A

Spiracles close
Abdomen muscles contract
Air is squeezed into the insect.

72
Q

What is the structure of the human breathing system?

A
  • lungs enclosed in the airtight thorax
  • pleural membrane line the thorax and cover each lung
  • diaphragm muscle at the base of the thorax separating it from the abdomen
  • ribs surround the thorax
  • intercostal muscles between ribs
  • trachea is a flexible airway into the lungs
  • two bronchi are branches of trachea
  • kings contain bronchioles which have air sacs (alveoli) at the end
73
Q

How do mammals ventilate their lungs?

A

Negative pressure breathing.

For air to enter the lungs pressure inside the lungs must be below atmospheric pressure.

74
Q

Why is breathing an active process?

A

Requires energy so that muscles can contract

75
Q

Describe inspiration for humans.

A
  • external intercostal muscles contract
  • ribs move up and out
  • at the same time, diaphragm muscles contract so it flattens
  • both actions increase the thorax volume
  • this reduces pressure in the lungs
  • atmospheric air pressure is now greater than pressure in the lungs so air is forced into the lungs.
76
Q

Describe expiration for humans.

A
  • external intercostal muscles relax
  • ribs move downwards and in
  • diaphragm relaxes and comes upwards.
  • both actions decrease thorax volume
  • this increases the pressure in the lungs
  • air pressure in the lungs is greater than atmospheric pressure so air is forces out of the lungs.
77
Q

How does lung tissue play a major role in pushing air out of the lungs?

A

The lung tissue is elastic and the lungs will recoil and regain their original shape when not being actively expanded.

78
Q

Surrounding each lung and lining the thorax there is a pleural membrane between which is a cavity filled with pleural fluid. How does this aid ventilation?

A

The pleural fluid acts as a lubricant allowing friction free movement against the inner wall of the thorax during ventilation.

79
Q

The inside surfaces of an alveoli are coated with surfactant (acts as an anti sticking mixture). It’s made of moist secretions containing phospholipid and protein. How does it aid the alveoli?

A
  • low surface tension preventing the alveoli collapsing during exhalation when that air pressure inside of them is low.
  • allows gases to dissolve before they can diffuse in or out.
80
Q

What is the gas exchange surface of a human?

A

The alveoli

81
Q

What make alveoli efficient at gas exchange?

A
  • large surface area in comparison to the volume of the body
  • gases dissolve in the surfactant moisture lining the alveoli
  • walls made of squamous epithelium only one cell thick so the diffusion pathway for gases is short
  • extensive network of capillaries surrounds alveoli and maintains diffusion gradient
  • capillary walls are one cell thick for short diffusion pathway for gases
82
Q

How does gas exchange occur over the alveolus?

A
  • Deoxygenated blood enters capillaries surrounding alveoli
  • oxygen diffuses out of the air in alveoli into red blood cells in capillary
  • carbon dioxide diffuses out of the plasma in the capillary into the air in the alveoli from where it is exhaled.
83
Q

Why do plants need to generate energy constantly?

A

They respire all the time

84
Q

What reactions occur in plants during the day?

A

Chloroplasts photosynthesis

Respiration

85
Q

How is carbon dioxide needed for photosynthesis provided to the plant?

A

Respiration

Diffusion into leaves

86
Q

How do plants get oxygen for respiration?

A

Through the roots and stem by diffusion

Leaves

87
Q

During the day why is oxygen the overall gas released from plants?

A

The rate of photosynthesis is greater than the rate of respiration and more oxygen is produced is photosynthesis than used in respiration.

88
Q

During the night why is carbon dioxide the main gas released?

A

Plants won’t photosynthesis me at night so no oxygen is produced. So the o my gas released is co2 produced from respiration.

89
Q

What is the structure of a leaf?

A
  • waxy cuticle
  • upper epidermis
  • palisade mesophyll
  • phloem and xylem
  • spongy mesophyll with air spaces
  • lower epidermis
  • waxy cuticle
  • stoma and guard cells
90
Q

What does a gas exchange surface need for sufficient diffusion?

A
  • short diffusion pathway
  • large concentration gradient
  • large surface area.
91
Q

What is the respiratory surface of a leaf?

A

The stomata

92
Q

What are two functions of a stomata?

A
  • oxygen to diffuse in to leaf

- prevent water loss

93
Q

How is water loss minimised from the l af?

A

Guard cells become flaccid and so the stomata closes.

94
Q

What parts of a leaf have adapted to make them more efficient?

A

-Cuticle=waxy to prevent water loss
-stomata= close at night to prevent water loss
Underside of leave out of direct sunlight
-spongy mesophyll = air space to allow gas to circulate and diffuse in and out cells
-thin leaf= short diffusion pathway
-palisade mesophyll = elongated cells with large surface area with large numbers of chloroplasts which arrange themselves according to light intensity for max photosynthesis

95
Q

What is a stomata?

A

Small pore on the underside of a leaf bound by two guard cells

96
Q

What is special about guard cells?

A

They are the only epidermal cells with chloroplasts and unevenly thickened walls.

97
Q

How do guard cells open the stomata?

A

Water enters the guard cell so that it becomes turgid and swells so that the pores open.

98
Q

How do guard cells close the stomata?

A

Water leaves the guard cells so they become flaccid and the pore closes.

99
Q

Why and how do guard cells become turgid to open up the stomatal pore?

A
  • chloroplasts in guard cells photosynthesise you produce ATP
  • ATP provides energy for active transport of potassium ions into cell
  • stores starch is converted into maleate
  • this lowers the water potential inside cell so water will enter by osmosis.
  • cell wall is thinner in some places than others.
  • guard cell expands as it absorbs water.
  • thicker walls on cells opposite each other stretch less as guard cell fills with water so pores appear.
100
Q

How do plants lose water?

A

By evaporation of water through the stomata during transpiration.

101
Q

What happens if plants lose too much water?

A

Plant wilts.

102
Q

When do stomata close to control water loss?

A
  • at night: to prevent water loss when there is insufficient light for photosynthesis
  • in very bright light: generally accompanied by intense heat which would increase evaporation
  • during excessive water loss.

A-level Biology (13 decks)

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