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unit 3 Exchange Of Substances Flashcards

1
Q

The relationship between surface
area to volume ratio and metabolic
rate for a smaller organism

A
  1. (Smaller so) larger surface area to volume ratio;
  2. More heat loss (per gram)
  3. Faster rate of respiration, releases more heat
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2
Q

Explain the advantage for larger
animals of having a specialised system
that facilitates oxygen uptake

A
  1. Large(r) organisms have a small(er) surface area:volume (ratio);
    OR
    Small(er) organisms have a large(r) surface area:volume (ratio);
  2. Overcomes long diffusion pathway
    OR
    Faster diffusion
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3
Q

Plants – explain why stomata open due to
increase in light intensity (1)

A

allowing carbon dioxide to enter for photosynthesis;
Or
for gas exchange allowing photosynthesis

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4
Q

Plants -Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf (4)

A
  1. (Carbon dioxide enters) via stomata; Reject stroma
  2. (Stomata opened by) guard cells;
  3. Diffuses through air spaces;
  4. Down diffusion gradient;
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5
Q

Plants – describe & explain an advantage
and disadvantage to having a higher stomatal density

A

Advantage
1. More carbon dioxide uptake;
2. More photosynthesis so faster/more growth;

Disadvantage
3. More water loss/transpiration
Accept plant wilts for ‘more water loss’
4. Less photosynthesis so slower/less growth;

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6
Q

Plants - Adaptations to desert plants (6)

A
  1. Hairs so ‘trap’ water vapour and water potential gradient decreased;
  2. Stomata in pits/grooves so ‘trap’ water vapour and water potential gradient decreased;
  3. Thick (cuticle/waxy) layer so increases diffusion distance;
  4. Waxy layer/cuticle so reduces
    evaporation/transpiration;
  5. Rolled/folded/curled leaves so ‘trap’ water vapour and
    water potential gradient decreased;
  6. Spines/needles so reduces surface area to volume ratio;
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7
Q

fish - counter-current mechanism (3)

A
  1. Water and blood flow in opposite directions;
  2. Blood always passing water with a higher oxygen concentration;
  3. Diffusion/concentration gradient (maintained) along (length of) lamella/filament;
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8
Q

Fish -Explain two ways in which the structure of fish gills is adapted for efficient gas exchange.(2)

A
  1. Many lamellae / filaments so large surface area;
  2. Thin (surface) so short diffusion pathway;
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9
Q

Insects - Describe & explain how the
structure of the insect gas exchange
system:
• provides cells with sufficient oxygen

A
  1. Spiracles (lead) to tracheae (that lead) to
    tracheoles;
  2. Open spiracles allow diffusion of oxygen from air
    OR
    Oxygen diffusion through tracheae/tracheoles;
  3. Tracheoles are highly branched so large surface area (for exchange);
  4. Tracheole (walls) thin so short diffusion distance (to cells)
    OR
    Highly branched tracheoles so short diffusion distance (to cells)
    OR
    Tracheoles push into cells so short diffusion distance;
  5. Tracheole walls are permeable to oxygen;
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10
Q

Insects - Describe & explain how the
structure of the insect gas exchange
system:
• limits water loss.(2)

A
  1. Cuticle/chitin in tracheae impermeable so reduce water loss;
  2. Spiracles close (eg.during inactivity) preventing water loss;
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11
Q

Insects - Abdominal Pumping (3)

A
  1. Abdominal pumping/pressure in tubes linked to carbon dioxide release;
  2. (Abdominal) pumping raises pressure in body;
  3. Air/carbon dioxide pushed out of body /air/carbon dioxide moves down pressure gradient (to atmosphere)
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12
Q

Insects -Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange.

A
  1. Tracheoles have thin walls so short diffusion distance to cells;
  2. Highly branched / large number of
    tracheoles so short diffusion distance to cells;
  3. Highly branched / large number of
    tracheoles so large surface area (for gas exchange);
  4. Tracheae provide tubes full of air so fast diffusion (into insect tissues);
  5. Fluid in the end of the tracheoles that moves out (into tissues) during exercise so faster diffusion through the air to the gas exchange surface;
    OR
    Fluid in the end of the tracheoles that moves out (into tissues) during exercise so larger surface area (for gas exchange);
  6. Body can be moved (by muscles) to move air so maintains diffusion / concentration gradient for oxygen / carbon dioxide;
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13
Q

Lungs - Describe and explain one feature
of the alveolar epithelium that makes the
epithelium wall adapted as a surface for gas exchange.

A

Mark in pairs
1. Flattened cells
OR
Single layer of cells;
Reject thin cell wall/membrane
Accept thin cells
Accept ‘one cell thick’

  1. Reduces diffusion distance/pathway;
  2. Permeable;
  3. Allows diffusion of oxygen/carbon dioxide;
  4. moist
  5. Increase rate of diffusion
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14
Q

Lungs – describe and explain inhaling (4)

A
  1. Diaphragm (muscle) contracts and external intercostal muscles contract;
    Ignore ribs move up and out
  2. (Causes volume increase and) pressure decrease;
  3. Air moves down a pressure gradient
    Ignore along
    OR
    Air enters from higher atmospheric pressure;
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15
Q

Lungs - Describe the pathway taken by an
oxygen molecule from an alveolus to
the blood. (2)

A
  1. (Across) alveolar epithelium;
  2. Endothelium of capillary;
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16
Q

Lungs - Explain how one feature of
an alveolus allows efficient gas exchange to occur.

A
  1. (The alveolar epithelium) is one cell thick;
    Reject thin membrane
  2. Creating a short diffusion pathway / reduces the diffusion distance;
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17
Q

Lungs - Describe the gross structure of
the human gas exchange system (1)

A
  1. Named structures – trachea, bronchi, bronchioles, alveoli;
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18
Q

Lungs – Describe how we breathe in and
out. (4)

A
  1. Breathing in – diaphragm contracts and external intercostal muscles contract;
  2. (Causes) volume increase and pressure decrease in thoracic cavity (to below atmospheric, resulting in air moving in);
    For thoracic cavity accept ‘lungs’ or ‘thorax’.
    Reference to ‘thoracic cavity’ only required once.
  3. Breathing out - Diaphragm relaxes and internal intercostal muscles contract;
    Accept diaphragm relaxes and (external) intercostal muscles relax and lung tissue elastic (so recoils).
  4. (Causes) volume decrease and pressure increase in thoracic cavity (to above atmospheric, resulting in air
    moving out);
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19
Q

Digestion – Proteins (4)

A
  1. Hydrolysis of peptide bonds;
  2. Endopeptidases break polypeptides into smaller peptide chains;
  3. Exopeptidases remove terminal amino acids;
  4. Dipeptidases hydrolyse/break down dipeptides into amino acids;
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20
Q

Digestion – Compare endopeptidase and
exopeptidase (3)

A
  1. Endopeptidases hydrolyse internal (peptide bonds); endopeptidase and
    exopeptidase
  2. Exopeptidases remove amino acids/hydrolyse (bonds) at end(s);
  3. More ends or increase in surface area (for exopeptidases);
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21
Q

Digestion - Describe the action of
membrane-bound dipeptidases and
explain their importance.(2)

A
  1. Hydrolyse (peptide bonds) to release amino acids;
  2. Amino acids can cross (cell) membrane by facilitated diffusion;
    OR
    Maintain concentration gradient of amino acids for absorption;
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22
Q

Digestion – Describe the complete
digestion of starch by a mammal.

A
  1. Hydrolysis;
  2. (Of) glycosidic bonds;
  3. (Starch) to maltose by amylase;
  4. (Maltose) to glucose by disaccharidase/maltase
  5. Disaccharidase/maltase membrane-bound;
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23
Q

Digestion - Function of bile salts and micelles (3)

A
  1. (Bile salts emulsify lipids forming) droplets which increase surface areas (for lipase / enzyme action);
  2. (So) faster hydrolysis / digestion (of triglycerides / lipids);
  3. Micelles carry fatty acids and glycerol /
    monoglycerides to / through membrane / to (intestinal epithelial) cell;
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24
Q

Digestion – describe lipid digestion (3)

A
  1. lipase hydrolyses triglycerides
  2. ester bonds
  3. Form monoglycerides and fatty acids
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25
Q

Digestion – Explain the advantages of
emmulsification and micelle formation.
(2)

A
  1. Droplets increase surface areas (for lipase / enzyme action);
  2. (So) faster hydrolysis / digestion (of triglycerides / lipids);
  3. Micelles carry fatty acids and glycerol /
    monoglycerides to / through membrane / to (intestinal epithelial) cell;
26
Q

Digestion – Explain the advantages of
emmulsification and micelle formation.
(2)

A

. Droplets increase surface areas (for lipase / enzyme action);

  1. (So) faster hydrolysis / digestion (of triglycerides / lipids);
  2. Micelles carry fatty acids and glycerol /
    monoglycerides to / through membrane / to (intestinal epithelial) cell;
27
Q

Absorption -Describe and explain two features you would expect to find in a cell
specialised for absorption. (4)

A
  1. Folded membrane/microvilli so large surface area (for absorption);
    Reject references to ‘villi’.
    Accept ‘brush border’ for ‘microvilli’.
  2. Large number of co-transport/carrier/channel proteins so fast rate (of absorption)
    OR
    Large number of co-transport/carrier proteins for active transport
    OR
    Large number of co-transport/carrier/channel proteins for facilitated diffusion;
  3. Large number of mitochondria so make (more) ATP (by respiration)
    OR
    Large number of mitochondria for aerobic respiration
    OR
    Large number of mitochondria to release energy for active transport;
  4. Membrane-bound (digestive)
    enzymes so maintains concentration gradient (for fast absorption);
28
Q

Absorption - Describe the processes
involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels. (4)

A
  1. Micelles contain bile salts and fatty
    acids/monoglycerides;
  2. Make fatty acids/monoglycerides (more) soluble (in water)
    OR
    Bring/release/carry fatty acids/monoglycerides to cell/lining (of the iluem)
    OR
    Maintain high(er) concentration of fatty
    acids/monoglycerides to cell/lining (of the ileum);
  3. Fatty acids/monoglycerides absorbed by simple diffusion;
  4. Triglycerides (re)formed (in cells);
    Accept chylomicrons form
  5. Vesicles move to cell membrane;
29
Q

Absorption - Describe the role of micelles
in the absorption of fats into the cells
lining the ileum (2)

A
  1. Micelles include bile salts and fatty acids;
    Ignore other correct components of micelles.
  2. Make the fatty acids (more) soluble in water;
    For ‘fatty acids’ accept fats / lipids.
  3. Bring/release/carry fatty acids to cell/lining (of the ileum);
    For ‘fatty acids’ accept fats/lipids.
  4. Maintain high(er) concentration of fatty acids to cell/lining (of the ileum);
  5. Fatty acids (absorbed) by diffusion;
30
Q

Absorption - how is the golgi apparatus
involved in the absorption of lipids.(3)

A
  1. Modifies / processes triglycerides;
  2. Combines triglycerides with proteins;
  3. Packaged for release / exocytosis
    OR
    Forms vesicles;
31
Q

Absorption – Explain how monosaccharides and amino acids are
absorbed into the blood (5)

A
  1. Some by facilitated diffusion (when higher concentration in lumen)
  2. Sodium ions actively transported from ileum cell to blood;
  3. Maintains / forms diffusion / concentration gradient for sodium to enter cells from gut (and with it, glucose);
  4. sodium ions enter cell by facilitated diffusion and bring with it a molecule of glucose by co-transport;
  5. Facilitated diffusion of glucose into blood/capillary;
32
Q

Haemoglobin - Binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind.
Explain why. (2)

A
  1. Binding of first oxygen changes tertiary / quaternary (structure) of haemoglobin;
    Ignore ref. to ‘positive cooperativity’ unqualified
    Ignore ref. to named bonds
    Accept conformational shift caused
  2. Creates / leads to / uncovers second / another binding site
    OR
    Uncovers another iron / Fe / haem group to bind to
33
Q

Haemoglobin -Explain how changes in the
shape of haemoglobin result in the S-shaped (sigmoid) oxyhaemoglobin
dissociation curve (2)

A
  1. First oxygen binds (to Hb) causing change in shape;
  2. (Shape change of Hb) allows more O2 to bind (easily) / greater saturation with O2
    OR
    Cooperative binding;
34
Q

Haemoglobin -Haemoglobin is a
protein with a quaternary structure.
Explain the meaning of quaternary
structure (1).

A

(Molecule contains) more than one polypeptide (chain)

35
Q

Haemoglobin -Describe the
advantage of the Bohr effect during
intense exercise. (2)

A
  1. Increases dissociation of oxygen;
    Accept unloading/ release/reduced affinity for dissociation
  2. For aerobic respiration at the tissues/muscles/cells
    OR
    Anaerobic respiration delayed at the
    tissues/muscles/cells
    OR
    Less lactate at the tissues/muscles/cells;
36
Q

Haemoglobin -Describe and explain the effect of increasing carbon dioxide
concentration on the dissociation of
oxyhaemoglobin. (2)

A
  1. Increases/more oxygen dissociation/unloading
    OR
    Deceases haemoglobin’s affinity for O2;
    Accept more readily
    Accept releases more O2
  2. (By) decreasing (blood) pH/increasing acidity;
37
Q

Haemoglobin – why curve shifts left when
diving (2)

A
  1. High(er) affinity for O2 (than haemoglobin)
    OR
    Dissociates oxygen less readily
    OR
    Associates more readily;
    Accept holds O2 at lower ppO2
  2. Allows (aerobic) respiration when diving/at low(er) pO2
    OR
    Provides oxygen when haemoglobin unloaded
    OR
    Delays anaerobic respiration/lactate production;
38
Q

Haemoglobin –Animals living at high altitudes shift to left (3)

A
  1. high altitudes have a low partial pressure of O2;
  2. high saturation/affinity of Hb with O2 (at low partial pressure O2);
  3. sufficient/enough O2 supplied to respiring cells / tissues;
39
Q

Haemoglobin – why small animals have
curved to the right (2)

A
  1. Curve to the right so lower affinity / % saturation (of haemoglobin);
  2. Haemoglobin unloads / dissociates more readily;
  3. More oxygen to cells / tissues / muscles;
  4. For greater / more / faster respiration;
40
Q

Haemoglobin – why curve to the right for
more active animals (2)

A
  1. Curve to the right so lower affinity / % saturation (of haemoglobin);
  2. Haemoglobin unloads / dissociates more readily;
  3. More oxygen to cells / tissues / muscles;
  4. For greater / more / faster respiration;
41
Q

Heart & circulation –dissection -three control measures the student must use to
reduce the risks associated with carrying and using a scalpel.

A
  1. Carry with blade protected / in tray
  2. Cut away from body;
  3. Cut onto hard surface;
  4. Use sharp blade;
  5. Dispose of used scalpel (blade) as instructed;
42
Q

Heart & circulation –dissection. Control
measures when packing away (2)

A
  1. Carry/wash sharp instruments by holding handle
    OR
    Carry/wash sharp instruments by pointing away (from body)/down;
    Accept for ‘instruments’, a suitable named example, eg. scalpel
  2. Disinfect instruments/surfaces;
    Accept for ‘instruments’, a suitable named example, eg. scalpel
    Accept for ‘disinfect’, sanitise OR use antiseptic
  3. Disinfect hands
    OR
    Wash hands with soap (and water);
    Accept for ‘disinfect’, sanitise OR use antiseptic
  4. Put organ/gloves/paper towels in a (separate) bag/bin/tray to dispose;
43
Q

Heart & circulation -Give the pathway a
red blood cell takes when travelling in
the human circulatory system from a kidney to the lungs. (3)

A
  1. Renal vein;
  2. Vena cava to right atrium;
  3. Right ventricle to pulmonary artery;
44
Q

Heart & circulation - Name the blood
vessels that carry blood to the heart muscle. (1)

A

Coronary arteries;

45
Q

Heart & circulation -Calculate Cardiac
Output (1)

A

Cardiac Output = Stroke Volume x Heart Rate

46
Q

Heart & circulation – what causes the semilunar valve to close (1)

A

Because pressure in aorta higher than in ventricle;

47
Q

Heart & circulation –explain how the
atrioventricular valve is closed (2)

A
  1. ventricle contracts and volume decreases
  2. pressure (ventricle) increases so higher than pressure of left atrium;
48
Q

Heart & circulation - Explain how an
arteriole can reduce the blood flow into
capillaries. (2)

A
  1. Muscle contracts;
  2. Constricts/narrows arteriole/lumen;
49
Q

Heart & circulation -Artery – Structure and
Function (5)

A
  1. Elastic tissue to allow stretching/recoil/ smooths out flow of blood/maintains pressure;
  2. (Elastic tissue) stretches when ventricles contract
    OR
    Recoils when ventricle relaxes;
  3. Muscle for contraction/vasoconstriction;
  4. Thick wall withstands pressure OR stop bursting;
  5. Smooth endothelium reduces friction;
50
Q

Heart & circulation - Explain four ways in
which the structure of the aorta is related to its function.

A
  1. Elastic tissue to allow stretching / recoil / smoothes out flow of blood / maintains pressure;
  2. (Elastic tissue) stretches when ventricles contract
    OR
    Recoils when ventricle relaxes;
  3. Muscle for contraction / vasoconstriction;
  4. Thick wall withstands pressure OR stop bursting;
  5. Smooth endothelium reduces friction;
  6. Aortic valve / semi-lunar valve prevents backflow.
51
Q

Heart & circulation Fish – describe type of
circulation in fish (1)

A
  1. Single circulatory system
    2 chambers/1 ventricle1 atrium
  2. One vein carrying blood towards the heart/ One artery carrying blood away
52
Q

Tissue fluid - Explain how water from
tissue fluid is returned to the circulatory system. (4)

A
  1. (Plasma) proteins remain;
    Accept albumin/globulins/fibrinogen for (plasma) protein
  2. (Creates) water potential gradient
    OR
    Reduces water potential (of blood);
  3. Water moves (to blood) by osmosis;
  4. Returns (to blood) by lymphatic system;
53
Q

Tissue fluid - Explain the role of the heart
in the formation of tissue fluid. (2)

A
  1. Contraction of ventricle(s) produces high blood / hydrostatic pressure;
  2. (This) forces water (and some dissolved
    substances) out (of blood capillaries);
54
Q

Tissue fluid - High absorption of salt
from the diet can result in a higher
than normal concentration of salt in the blood plasma entering capillaries. This can lead to a build-up of tissue fluid.
Explain how. (4)

A
  1. (Higher salt) results in lower water potential of tissue fluid;
  2. (So) less water returns to capillary by osmosis (at venule end);
    OR
  3. (Higher salt) results in higher blood pressure / volume;
  4. (So) more fluid pushed / forced out (at arteriole end) of capillary;
55
Q

Tissue fluid - High blood pressure
leads to an accumulation of tissue fluid. Explain how. (2)

A
  1. High blood pressure = high hydrostatic pressure;
  2. Increases outward pressure from (arterial) end of capillary / reduces inward pressure at (venule) end of capillary;
  3. (So) more tissue fluid formed / less tissue fluid is reabsorbed.
56
Q

Tissue fluid -Formation and reabsorption (8)

A
  1. At arteriole end high hydrostatic pressure/blood pressure;
  2. Hydrostatic pressure higher than effect of osmosis;
  3. Small molecules/named example eg glucose; water
  4. Forces out;
  5. Proteins remain in blood/ not removed as they are too large to leave capillary;
  6. Increasing/giving higher concentration of blood proteins so proteins lower water potential of blood;
  7. Water/fluid moves back into blood;
  8. Water moves by osmosis
57
Q

Water - Describe the cohesion-tension
theory of water transport in the xylem. (5)

A
  1. Water lost from leaf because of transpiration / evaporation of water (molecules) / diffusion from mesophyll / leaf cells;
    OR
    Transpiration / evaporation / diffusion of water (molecules) through stomata / from leaves;
  2. Lowers water potential of mesophyll / leaf cells;
  3. Water pulled up xylem (creating tension);
  4. Water molecules cohere / ‘stick’ together by hydrogen bonds;
  5. (forming continuous) water column;
  6. Adhesion of water (molecules) to walls of xylem
58
Q

Water - T A potometer measures the rate of water uptake rather than the rate of transpiration. Give two reasons why the potometer does not truly measure the rate of transpiration. (2)

A
  1. Water used for support / turgidity;
    Accept: water used in (the cell’s) hydrolysis or
    condensation (reactions) for one mark. Allow a named example of these reactions
  2. Water used in photosynthesis;
  3. Water produced in respiration;
  4. Apparatus not sealed / ‘leaks’;
59
Q

Water - Give two precautions the students
should have taken when setting up the
potometer to obtain reliable measurements of water uptake by the
plant shoot. (2)

A
  1. Seal joints / ensure airtight / ensure watertight;
    Answer must refer to precautions when setting up the apparatus
    Ignore: references to keeping other factors constant
  2. Cut shoot under water;
  3. Cut shoot at a slant;
  4. Dry off leaves;
  5. Insert into apparatus under water;
  6. Ensure no air bubbles are present;
  7. Shut tap;
  8. Note where bubble is at start / move bubble to the start position;
60
Q

Sucrose - Describe the transport of
carbohydrate in plants. (5)

A
  1. (At source) sucrose is transported into the phloem/sieve element/tube;
  2. By active transport
    OR
    By co-transport with H+;
    Accept co-transport with hydrogen/H ions
  3. By companion/transfer cells;
  4. Lowers water potential in phloem and water enters by osmosis;
    Accept pressure gradient
    For ‘phloem’ accept ‘sieve element/tube’.
  5. (Produces) high (hydrostatic) pressure;
  6. Mass flow;
  7. Transport from site of photosynthesis to respiring cells
    OR
    Transport from site of photosynthesis to storage organ
    OR
    Transport from storage organ to respiring cells;
61
Q

Sucrose - Use your understanding of the
mass flow hypothesis to explain how
pressure is generated inside this phloem tube. (3)

A
  1. Sucrose actively transported (into phloem);
  2. Lowering/reducing water potential
    OR
    More negative water potential;
  3. Water moves (into phloem) by osmosis (from xylem);
62
Q

Sucrose - Phloem pressure is reduced
during the hottest part of the day. Use
your understanding of transpiration and
mass flow to explain why. (3)

A
  1. High (rate of) transpiration/evaporation;
  2. Water lost through stomata
    OR
    (High) tension in xylem;
  3. (Causes) less water movement from xylem to phloem
    OR
    Insufficient water potential in phloem to draw water from xylem;

. (9 decks)

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