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Biology Unit 2 > 2.2 Adaptations For Gas Exchange > Flashcards

2.2 Adaptations For Gas Exchange Flashcards

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1
Q

What is gas exchange

A

The process where gases move passively by diffusion across a surface. Essential gases are transported into cells and waste products carried away

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2
Q

What are the gases transported into cells essential for

A

Essential for process like respiration and photosynthesis

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3
Q

What is the respiratory surface

A

The body surface where gaseous exchange by diffusion happens over

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4
Q

What are the characteristics of respiratory surfaces needed to maintain the maximum rate of diffusion

A
  • thin (so diffusion pathway is short)
  • permeable to the gases
  • moist (so gases can dissolve)
  • large surface area to volume ratio (so rate of gas exchange is sufficient to satisfy the organism’s needs)
  • mechanism with steep concentration gradient
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5
Q

Why is it bad that larger organisms’ cells are a bigger distance away from the respiratory surface

A

Gases can’t reach or be carried away from these cells quickly enough by simple diffusion alone

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6
Q

What kind of organisms have a large surface area to volume ratio

A

Tiny organisms like the single celled amoeba.

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7
Q

Why is it good to have a large surface area to volume ratio

A

So gases can diffuse quickly enough throughout the organism

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8
Q

What kind of organisms have a smaller surface area to volume ratio

A

Huge organisms like elephants and whales.

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9
Q

Why and with what are large organisms adapted with to help gas exchanhe

A

Must be adapted with specialised respiratory surfaces, circulatory systems, and blood pigments to facilitate the transport of gases around their bodies

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10
Q

Why have large multi cellular organisms evolved specialised respiratory surfaces for gas exchange

A
  • metabolic needs are proportional to volume, so larger organisms need more oxygen.
  • the external surface of larger organisms is insufficient for gas exchanges.
  • diffusion of respiratory gases is proportional to surface area, so in larger organisms the surface area to volume ratio is too small to achieve gas exchange since diffusion distances are too large.
  • not enough oxygen can diffuse to all the cells in time to supply their metabolic needs
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11
Q

How do small unicellular organisms exchange gases

A

They exchange gases across the cell surface. Their surface are to volume ratio is large enough to supply their needs. Distances within the cel are small so diffusion is rapid enough.

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12
Q

Gas exchange in amoeba

A
  • unicellular
  • large surface area to volume ratio.
  • no specialised surfaces
  • aquatic so water loss from surface isn’t a problem.
  • uses its general body surface for gas exchange. Gets oxygen dissolved from surrounding water through its plasma membrane in simple diffusion
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13
Q

Gas exchange in flatworm

A
  • multicellular
  • large surface area to volume ratio due to flattened shape
  • no specialised surfaces for gas exchange
  • aquatic so no water loss from surface
  • gas exchange occurs by passive diffusion through body wall/surface
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14
Q

Gas exchange in earthworm

A
  • multicellular
  • large surface area to volume ratio due to cylindrical shape
  • a simple circulatory system. Blood pigments transport gases throughout body.
  • terrestrial, so water loss from surface is a problem.
  • gas exchange happens through moist skin and capillaries. As fresh air is taken in through the skin, oxygen drawn into worm’s circulatory system
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15
Q

Why are bony fish’s oxygen needs greater than other organisms

A

larger and more active

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16
Q

What are bony fish’s specialised gas exchanges surface

A

the gills

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17
Q

Explain gills as a specialised gas exchange surface

A

Gills have large surface area due to gill filaments (a specialised respiratory area).
Water forced over gill filaments

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18
Q

Why must water be forced over the gill filaments

A

Because water is a dense medium with relatively low oxygen content

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19
Q

How is water forced over the gills

A

by a ventilating mechanism

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20
Q

What prevents the gills from collapsing to maintain the large surface area

A

The density of water

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21
Q

Flow of water is…

A

One way / unidirectional

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22
Q

Direction of water in bony fish

A

Water in through mouth and out through gills

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23
Q

What does the system of ventilation in a bony fish allow

A

allows water to be passed continuously across the gills even when the fish is resting

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24
Q

How is ventilation achieved

A

By pressure changes in buccal (mouth) and opercular (gill) cavities

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25
Q

When buccal/mouth is open, what is the operculum/gill

A

Closed

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26
Q

Stage 1 of ventilation process

A

Mouth opens, floor if buccal cavity lowered.
Volume of buccal cavity increases and pressure decreases.
The operculum remains closed.
Water is pulled into buccal cavity from outside due to change in pressure

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27
Q

Stage 2 of ventilation process

A

Mouth closes and buccal cavity contracts, raising the floor of the buccal cavity.
Water forced across the gills

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28
Q

Stage 3 of ventilation process

A

Pressure in gill cavity increases and forces operculum open.
Water leaves via the operculum

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29
Q

What does an extensive network of capillaries in gills allow?

A

Allow efficient diffusion of oxygen

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30
Q

What does the blood pigment haemoglobin and circulatory system do in fish

A

Carry oxygen throughout the fish

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31
Q

What do gill filaments have

A

Gill plates or lanellae

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32
Q

Where does water flow in gill capillaries

A

Water flows between gill plates (lamellae) in opposite direction to blood flow

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33
Q

What does counter current flow do (positive)

A

Increases efficiency of diffusion by maintaining a steep concentration gradient across the whole gill filament.
Blood always meets water with a relatively high oxygen content

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34
Q

Water flows in what direction with blood

A

Water flows in opposite direction than blood

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35
Q

How to identify oxygen vs blood on a graph of counter current flow

A

Water always contains more oxygen so always higher on graph

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36
Q

Why do cartilaginous fish like sharks have a more inefficient system

A

Parallel flow - Water and blood flow in same direction across gill plate.

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37
Q

What is a parallel flow

A

Water and blood flow in same direction across gill plate

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38
Q

Why is parallel flow less efficient than counter current flows

A

Steep concentration gradient isn’t maintained and rate of diffusion isn’t optimum across entire gill plate. Good in beginning but oxygen in both blood and water will eventually be at equilibrium so there’s no net movement.

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39
Q

Why can’t sharks stop swimming

A

To prevent suffocation. Because of inefficient nature of their ventilation system. Need movement for water to get in, to receive oxygen from it

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40
Q

Compare Counter current flow and parallel flow

A
  • CCF water flows across filament in opposite direction to blood flow in gill capillaries. PF water flows across filament in same direction as blood flow in gill capillaries.
  • CCF steep concentration gradient is maintained. PF oxygen concentration gradient isn’t maintained and equilibrium is reached
  • CCF diffusion of oxygen from water to blood occurs across entire gill plate. Doesn’t in PF
  • CCF rate of diffusion high. Lower in PF as equilibrium is reached
  • CCF greater amount of oxygen absorbed into blood. Higher oxygen saturation percentage. PF less oxygen absorbed into blood. Lower percentage oxygen saturation of blood
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41
Q

Characteristics of respiratory surface in amphibians, reptiles and birds

A
  • large surface area
  • moist surface
  • short diffusion pathway
  • circulatory system with blood pigments
  • internal lungs
  • ventilation mechanism
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42
Q

Positives of large surface area in respiratory surface

A

For rapid diffusion of respiratory gases

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43
Q

Positives of moist surface in respiratory surface

A

To facilitate rapid diffusion of gases

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44
Q

Positives of short diffusion patheay in respiratory surface

A

Thin walls so easier to diffuse through

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45
Q

Positives of circulatory system with blood pigments in respiratory surface

A

To carry oxygen. E.g haemoglobin

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46
Q

Positives of internal lungs in respiratory surface

A

Minimise loss of water and heat

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47
Q

Positives of ventilation mechanism in respiratory surface

A

Forces respiratory medium (air) to and from respiratory surface. To ensure oxygen is brought to and carbon oxide is removed from the gas exchange surface

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48
Q

How do inactive amphibians do gas exchange

A

Use their moist skin

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49
Q

How do active amphibians do gas exchange

A

Use simple lungs.
Frog lungs pair of hollow sacs with highly folded surface to increase surface area.

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50
Q

How do tadpoles do gas exchange

A

Uses gills

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51
Q

Why can’t reptilian skin be used as a respiratory surface

A

Impermeable to gases

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52
Q

Why are reptile lungs more efficient than amphibians

A

Reptilian lungs sac-like and have more complex folding than amphibian lungs. Reptiles have ribs as well

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53
Q

How is ventilation aided in reptiles

A

Aided by movement of ribs by the intercostal muscles

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54
Q

What does ventilation mean

A

Actively moving the respiratory medium across the respiratory surface

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55
Q

What is the respiratory surface

A

Where gases are exhanged

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56
Q

Why is efficient gas exchange essential in birds

A

They’re warm blooded and have a high respiration rate

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57
Q

Structure of bird lungs

A

Small, compact, composed of numerous branching air tubes called bronchi

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58
Q

What do the smallest air tubes (parabronchi) have?

A

Have an extensive blood capillary network where gas exchange takes place

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59
Q

How does structure of parabronchi help gas exchange

A

Parabronchi end in large, thin walled air sacs which help in ventilation.
No diaphragm but do have ribs and flight muscles for efficient ventilation

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60
Q

What can cause dehydration in terrestrial organisms

A

Water evaporates from the body surface

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61
Q

What does efficient gas exchange require

A

A thin, permeable surface with a large surface area

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62
Q

What have insects evolved to reduce water loss

A

Evolved a rigid waterproof exoskeleton, which is covered by a cuticle

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63
Q

Why can’t insects use their body surface to exchange gases by diffusion?

A

Have a relatively small surface area to volume ratio

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64
Q

What system of gas exchange have insects evolved, different to other land animals

A

The tracheal system

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65
Q

In the tracheal system of insects, where does gas exchange occur

A

Through spiracles (paired hole running along side of body)

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66
Q

Structure of tracheal system

A

Paired holes called spiracles run along side of the insect’s body. Spiracles lead into a system of branched, chitin lined air-tubes called tracheae

67
Q

What is tracheae

A

A system of branched, chitin lined air tubes

68
Q

What do spiracles do?

A

Can open and close like valves to allow gas exchange to take place and reduces water loss

69
Q

What do resting insects rely on

A

Rely on diffusion to take in oxygen and remove carbon dioxide

70
Q

What happens to insects during periods of activity (e.g flight)

A

Movements of the abdomen ventilate the tracheae

71
Q

What are the ends of the tracheae called?

A

Tracheoles

72
Q

What are tracheoles

A

A gas exchange surface

73
Q

What is NOT needed to transport the oxygen in tracheal system

A

A respiratory pigment like haemoglobin, and a circulatory system isn’t needed to transport oxygen

74
Q

Why aren’t respiratory pigments like haemoglobin and a circulatory system needed to transport oxygen in a tracheal system?

A

Tracheoles are in direct contact with the cells and tissues so oxygen is passed DIRECTLY to the cells. It’s very rapid

75
Q

How structure of muscle fibres connected to tracheoles help gas exchange

A

Never exceed 20um in diameter which provides short diffusion path for gas exchange. So, diffusion is rapid enough to supply sufficient oxygen to the cells and tissues

76
Q

What happens to tracheoles during insect flight and how does this help gas exchange

A

Fluid levels in the tracheoles decrease during flight to provide more surface area for gas exchange and also further shortens diffusion pathway

77
Q

What ventilates the tracheal system in insects

A

Compression and expansion of the abdomen

78
Q

What does ventilation do

A

Ventilation carries the respiratory medium (air) to the respiratory surface at the end of the tracheoles

79
Q

What do spiracles do

A

Open and close to allow air in and out of tracheal system

80
Q

Order of spiracles opening

A

Thorax spiracles open first, just before the abdominal spiracles. Both open for the same length.

81
Q

Spiracles closed for a long period of time to…

A

Prevent water loss

82
Q

Abdomen shape relationship to spiracles

A

Thorax spiracles open as the abdomen expands, abdomen is compressed before abdomen spiracles open.

83
Q

What does the compression and expansion of the abdomen do?

A

Act as a pump to draw air in via the thorax spiracles, through the system and forces it out via the abdominal spiracles

84
Q

What is the thorax

A

An airtight compartment where the lungs are enclosed within

85
Q

Function of epiglottis

A

Valve which prevents food getting into trachea

86
Q

Function of trachea

A

Carries air to bronchi

87
Q

Function of cartilage rings

A

Helps support trachea while still allowing it to move and flex during breathing

88
Q

Function of bronchi

A

Carries air to bronchioles

89
Q

Function of bronchioles

A

Carries air to alveoli

90
Q

Function of alveoli

A

Respiratory surface where gas exchange occurs

91
Q

Function of diaphragm

A

Separates thorax and abdomen and helps ventilate lungs

92
Q

Function of ribs

A

Protect lungs and ventilation

93
Q

Function of intercostal muscles

A

Move the ribs

94
Q

Function of pleural membranes

A

Secrete fluid into the space between them which prevents damage to lungs due to friction

95
Q

Ventilation in humans meaning

A

Ventilation is a mechanism which moves the respiratory medium (air) to and from the respiratory surface (the alveoli)

96
Q

How do mammals ventilate their lungs

A

By negative pressure breathing, forcing air down into the lungs

97
Q

How do intercostal muscles carry out inspiration and expiration

A
  • inspiration : contract
  • expiration : relax
98
Q

How do ribs carry out inspiration and expiration

A

Inspiration : move up and out
Expiration : moves back down and in

99
Q

How does diaphragm carry out inspiration and expiration

A

Inspiration : contracts and flattens
Expiration : relaxes and domes

100
Q

How does volume of thorax carry out inspiration and expiration

A

Inspiration : increases
Expiration : decreases

101
Q

How doors pressure of thorax carry out inspiration and expiration

A

Inspiration : decreases
Expiration : increases

102
Q

How does outside air pressure carry out inspiration and expiration

A

Inspiration: greater than the pressure in the thorax; air is forced into lungs.

Expiration : pressure inside lungs greater than outside; air is forced out of lungs

103
Q

If diaphragm is flat and ribcage has moved up and out, is it inspiration or expiration

A

Inspiration. We can tell thorax is contracting

104
Q

What surrounds each lung and lines the thorax

A

Pleural membranes

105
Q

What does the cavity between membranes contain

A

Pleural fluid

106
Q

What does pleural fluid do

A

When breathing, this fluid acts as a lubricant, allowing friction free movement against wall of thorax

107
Q

What is the gas exchange surface in mammals

A

The alveoli

108
Q

Characteristics of alveoli to help with gas exchange

A
  • large surface area to volume ratio.
  • moist surface for gases to dissolve.
  • thin walls for short diffusion pathway
109
Q

Structure of surface of alveoli

A

One cell thick and composed of squamous epithelium tissue.

110
Q

Each alveolus is covered by an…

A

Extensive capillary network

111
Q

What maintains a steep concentration gradient for diffusion in the alveoli

A

Oxygenated blood is carried away from the alveolus and blood rich in carbon dioxide returns

112
Q

What is a surfactant

A

Anti sticking chemical

113
Q

What do surfactants do

A

Cover surface of each alveolus, which prevents alveoli collapsing when breathing out (by reducing surface tension)

114
Q

Who are surfactants often given to

A

Premature babies to prevent the alveoli in their immature lungs sticking together

115
Q

Composition of air in lungs - OXYGEN

A

% of oxygen in alveolus lower than in inspired air.
% of oxygen in expired air lower than in inspired air

Inspired air : 20
Alveolar air : 14
Expired air : 16

116
Q

Composition of air in the lungs - CARBON DIOXIDE

A

% of carbon dioxide in the alveolus is higher than in inspired air.
% of carbon dioxide is in expired air is higher than in inspired air.

Inspired air : 0.4
Alveolar air : 6
Expired air : 4

117
Q

Composition of air in lungs - NITROGEN

A

% of nitrogen in the alveolus is similar than in inspired air.
% of nitrogen is in expired air is similar than in inspired air (Not much taken in)

Inspired air : 79
Alveolar air : 80
Expired air : 79

118
Q

Composition of air in lungs - WATER VAPOUR

A

Inspired air: variable
Alveolar air : saturated
Expired air : saturated

119
Q

Why is the percentage oxygen in the alveolus lower than in inspired air

A

Because it mixes with air already in the lungs, which had lower percentage oxygen content

120
Q

Why does inspired air have more % of oxygen than expired air

A

Oxygen is absorbed into the red blood cells at the alveoli and used in aerobic respiration.

121
Q

Why does expired air have more % of carbon dioxide than inspired air

A

Carbon dioxide produced by respiration diffuses from the blood plasma into the alveoli

122
Q

Why does inspired air have the same % of nitrogen than expired air

A

Nitrogen isn’t absorbed or used so all that is inhaled gets exhaled

123
Q

Why does inspired air have more variable water vapour, whereas expired air has more saturated water vapour

A

The water content of the atmosphere varies. Alveoli are permanently lined with moisture; water evaporates from them and is exhaled

124
Q

How to calculate % of oxygen extracted

A

% oxygen absorbed / % air that is oxygen
X 100

125
Q

Why do plants need to exchange gases

A

For respiration and photosynthesis

126
Q

What is the main gas exchange surface in plants

A

The leaf

127
Q

What happens to plants during the day

A

They respire and photosynthesise

128
Q

What happens to plants during the night

A

Photosynthesis stops but respiration continues

129
Q

During the day, most if the carbon dioxide plants need for photosynthesis…

A

Diffuses into the leaf from the air. And some is provided by respiration

130
Q

In plants, most of the oxygen produced by photosynthesis…

A

Diffuses out of the leaves

131
Q

At night, the oxygen needed for respiration… (in plants)

A

Diffuses into the leaf from the atmosphere

132
Q

How does the structure of a leaf relate to its function

A

The leaf blade (lamina) is thin and flat, with a large surface area.
Diffusion pathways for gases are short

133
Q

Function of waxy cuticle

A

Prevents water loss. Transparent to let light in

134
Q

Function of upper epidermis

A

Transparent and thin to allow light to penetrate through leaf

135
Q

Function of palisade mesophyll

A

Packed with chloroplasts for photosynthesis

136
Q

Function of spongy mesophyll

A

The gaps allows for the circulation of gases. Contains chloroplasts for photosynthesis

137
Q

Function of air spaces

A

Allows carbon dioxide to diffuse into the cells and oxygen out (during the day for photosynthesis)

138
Q

Function of guard cells

A

Open and close the stomata

139
Q

Function of stomatal pores

A

For gas exchange

140
Q

Function of lower epidermis

A

Thin and contains waxy cuticle

141
Q

Function of vascular bundles (xylem and phloem)

A

Provides the leaf with water and minerals

142
Q

Adaptations of the leaf for gas exchange

A
  • spongy mesophyll tissue : many air spaces for circulation of gases.
  • stomatal pores : allow gases to exchange between outside air and leaf
143
Q

Steps of CO2 gas exchange in leaf

A
  • carbon dioxide diffuses through stomata down a concentration gradient.
  • carbon dioxide then circulated the intercellular spaces between mesophyll cells, by diffusion
  • carbon dioxide dissolves in the moist layer, which covers each cell, and diffuses into the mesophyll cells, across the cell membrane
144
Q

Adaptations of leaf for photosynthesis

A
  • large surface area
  • can orientate themselves
  • thin
  • cuticle and epidermis are transparent
  • palisade mesophyll cells
  • chloroplasts can rotate and move within the mesophyll cells
145
Q

How does large surface area in leaf help photosynthesis

A

captures as much light as possible

146
Q

How does leaves’ ability to orientate help photosynthesis

A

So they’re held at perpendicular angle to the sun, to expose the surface to as much light as possible.

147
Q

How does thinness of leaves help photosynthesis

A

To allow light to penetrate to lower cell layers.

148
Q

How does a transparent cuticle and epidermis help with photosynthesis in leaves

A

to allow light to penetrate to the mesophyll.

149
Q

How do palisade mesophyll layers help with photosynthesis

A

are elongated and densely arranged in layers to allow more chloroplasts

150
Q

How do chloroplasts being able to rotate and move help with photosynthesis in leaves

A

Allows them to arrange themselves in the best possible position for light absorption.

151
Q

How do intercellular spaces and spongy mesophyll help with photosynthesis in leaves

A

Allow gases to circulate. CO2 diffuses into the cells and oxygen diffuses out the cells

152
Q

What are stomata

A

Pores which allow the exchange of gases. Water is lost through stomata

153
Q

Each stomata is bounded by…

A

2 guard cells

154
Q

Structure of guards cells

A
  • Have thick inner wall and thin outer wall.. Thick inner wall causes cell to become a curves sausage shape when it swells: opens stomatal pore
  • Have chloroplasts.
155
Q

What do guard cells do

A

Can change shape to open and close the stomata: this controls gas exchange and water loss

156
Q

What happens to plants if they lose too much water

A

They wilt/cells become flaccid

157
Q

Why do most stomata close at night

A

To prevent the plant needlessly losing water when the light intensity is too low for photosynthesis

158
Q

If light strikes the upper leaf surface, why are stomata found on lower leaf surface

A

To reduce water loss

159
Q

Why do guard cells change shape

A

Due to a change in turgor:

160
Q

What happens when water ENTERS the guard cells

A

When water ENTERS the guard cells by osmosis, the guard cells swell/become turgid. This opens the stomatal pore since the thicker inner wall causes the guard cell to curve.

161
Q

What happens when water LEAVES the guard cells

A

When water LEAVES the guard cells by osmosis they become flaccid which closes the stomatal pore

162
Q

Stomata opening mechanism

A
  • during the day (if light intensity is sufficient) potassium ions (K+) are pumped by active transport into the guard cells.
  • as a result, stored starch is converted to malate.
  • this lowers the water potential (becomes more negative)
  • water enters cell by osmosis.
  • guard cells become turgid and curve apart because their outer walls are thinner than their inner walls.
  • this opens the stomatal pore, allowing gas exchange
163
Q

Stomata closing mechanism

A
  • when light intensity is too low for photosynthesis, potassium ions diffuse down a concentration gradient out the guard cells.
  • Malate is converted back into starch by condensation reaction.
  • The water potential of the guard cells increases (becomes less negative).
  • water leaves the guard cells by osmosis.
  • guard cells become flaccid which closes the stomatal pore.
  • this prevents gas exchange and reduces water loss
164
Q

Magnification calculation

A

Size of image / actual size

Biology Unit 2 (2 decks)

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