3 Organisms exchange substances with their environment EQs Flashcards
(163 cards)
1
Q
How is the pressure in the ventricle related to the thickness of the ventricle wall? (2 marks)
A
- Thickness of wall increases because ventricle wall contracts
- Contraction causes the increase in pressure
2
Q
The hydrostatic pressure falls from the arteriole end of the capillary to the venule end of the capillary. Explain why. (1 mark)
A
Loss of water
3
Q
High blood pressure leads to an accumulation of tissue fluid. Explain how. (3 marks)
A
- High blood pressure = high hydrostatic pressure
- Increases outward pressure from arterial end of capillary
- So more tissue fluid formed
4
Q
The water potential of the blood plasma is more negative at the venule end of the capillary than at the arteriole end of the capillary. Explain why. (3 marks)
A
- Water has left the capillary;
- Proteins in blood too large to leave capillary;
- Higher concentration of blood proteins and so lowers water potential
5
Q
An increase in the concentration of carbon dioxide would change the internal environment and blood pH.
Explain the importance of maintaining a constant blood pH. (3 marks)
A
- Haemoglobin affected by change in pH
- Change of tertiary structure;
- Increases dissociation
e.g. less oxygen binds with haemoglobin
6
Q
Other than causing slow blood flow, explain one advantage of capillaries being narrow. (2 marks)
A
- Short distance between blood and outside of capillary
- Fast exchange
7
Q
What factor limits the minimum internal diameter of the lumen of a capillary? (1 mark)
A
Size of blood cell.
8
Q
The volume of blood leaving the capillary network into the veins is less than the volume of blood entering from the arteries.
Explain why. (1 mark)
A
Fluid in tissue fluid
9
Q
What is the function of the coronary arteries? (2 marks)
A
- Carry oxygen
- To heart muscle
10
Q
The rise and fall in blood pressure in the aorta is greater than in the small arteries. Suggest why. (3 mark)
A
- Aorta is directly linked to the heart
- Aorta has elastic tissue;
- Aorta has stretch / recoil.
11
Q
The scientists used the percentage change in the mean resting heart rate after the
exercise programme to compare the results for males and females.
Explain why they used percentage change in the resting heart rate. (2 marks)
A
- Allows comparison
- Initial heart rates different between males and females
12
Q
Explain how their cardiac output could stay the same even when their resting heart
rate had decreased in an exercise programme? (2 marks)
A
- Cardiac output = stroke volume × heart rate
- So stroke volume increases
13
Q
Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs. (3 marks)
A
- Renal vein;
- Vena cava to right atrium;
- Right ventricle to pulmonary artery;
14
Q
Tissue fluid is formed from blood at the arteriole end of a capillary bed. Explain how water from tissue fluid is returned to the circulatory system. ( 4 marks)
A
- Plasma proteins remain;
- Creates water potential gradient
- Water moves to blood by osmosis;
- Returns to blood by lymphatic system;
15
Q
Explain how an arteriole can reduce the blood flow into capillaries. (2 marks)
A
- Muscle contracts;
- Narrows lumen;
16
Q
What blood vessel carries blood at the lowest
blood pressure? (1 mark)
A
Vena Cava
17
Q
The pressure in the left ventricle is increasing.
At this time, the rate of blood flow has not yet started to increase in the aorta. Explain why (2 marks)
A
- Semi-lunar valves is closed;
- Because pressure in aorta higher than in ventricle;
18
Q
There is a small increase in pressure and in rate of blood flow in the aorta.
Explain how this happens and its importance. (2 marks)
A
- Elastic recoil of the aorta wall
- Maintains blood pressure
19
Q
EPO is another performance-enhancing drug. It can increase the haematocrit (the percentage of red blood cells in blood). A heart attack is caused by a lack of glucose and oxygen being delivered to cardiac muscle via the coronary arteries. The overuse of EPO can increase the risk of a heart attack.
Suggest how. (2 marks)
A
- EPO causes blood to thicken;
- The thickened blood could block the coronary arteries
20
Q
Describe and explain the effect of increasing carbon dioxide concentration
on the dissociation of oxyhaemoglobin. (2 marks)
A
- More oxygen dissociation
- By decreasing blood pH
21
Q
Give two safety precautions that should be followed when dissecting a
heart. (1 mark)
A
- Wash hands/wear gloves
- Disinfect bench/equipment
22
Q
Explain how left atrioventricular valve maintains a unidirectional flow of blood. (2 marks)
A
- Pressure in left atrium is higher than in ventricle causing valve to open;
- Pressure in left ventricle is higher than in atrium causing valve to close;
23
Q
Explain the role of the heart in the formation of tissue fluid. (2 marks)
A
- Contraction of ventricle produces high hydrostatic pressure;
- This forces water out of blood capillaries
24
Q
Lymphoedema is a swelling in the legs which may be caused by a blockage in the lymphatic system.
Suggest how a blockage in the lymphatic system could cause
lymphoedema. (1 mark)
A
Excess tissue fluid builds up
25
Why is putting a replacement organ in an isotonic solution important? (2 marks)
1. Because same water potential;
2. So prevents loss or gain of water by osmosis
3. So cells aren’t damaged;
26
Why is putting a replacement organ in an antibiotic important? (1 mark)
Kills bacteria that could cause infection
27
Describe the mass flow hypothesis for the mechanism of translocation in plants. (4 marks)
1. In source sugars actively transported into phloem;
2. By companion cells;
3. Lowers water potential of sieve cell and water enters by osmosis;
4. Increase in pressure causes mass movement towards sink
5. Sugars used in root for respiration for storage.
28
What other information is required in order to calculate the mean rate of movement down a trunk of a tree? (1 mark)
Length of trunk
29
Describe how a high pressure is produced in the leaves. (3 marks)
1. Water potential becomes lower as sugar enters phloem
2. Water enters phloem by osmosis
3. Increased volume of water causes increased pressure.
30
Suggest and explain one other way in which sieve cells are
adapted for mass transport. (2 marks)
1. Few organelles
2. So more flow
31
Suggest and explain one other way in which companion
cells are adapted for the transport of sugars between cells. (2 marks)
1. Mitochondria release energy
2. For active transport
32
The mass flow hypothesis is used to explain the movement of substances through phloem.
Use your understanding of the mass flow hypothesis to explain how pressure is generated inside this phloem tube. (3 marks)
1. Sucrose actively transported into phloem
2. Lowering water potential
3. Water moves into phloem by osmosis from xylem
33
Phloem pressure is reduced during the hottest part of the day. Use your understanding of
transpiration and mass flow to explain why. (3 marks)
1. High rate of transpiration
2. Water lost through stomata
3. Causes less water movement from xylem to phloem
34
Suggest how a plant is able to survive without xylem tissue. (1 mark)
It has a surface permeable to water
35
The student wanted to determine the rate of water loss per mm2 of surface area of the leaves of a shoot. Outline a method she could have used to find this rate. You should assume that all water loss from the shoot is from the leaves. (3 marks)
1. Method for measuring area;
e.g. draw round each leaf on graph paper and count squares;
2. Of both sides of each leaf;
3. Divide rate by total surface area of leaves
36
The rate of water movement through a shoot in a potometer may not be the same as the rate of water movement through the shoot of a whole plant.
Suggest one reason why. (1 mark)
Plant has roots
37
Describe the mechanism for the absorption of amino acids in the ileum (4 marks)
1. Co-transport;
2. Sodium ions actively transported from cell to blood
3. Creating sodium ion concentration gradient;
4. Facilitated diffusion of amino acid into blood
38
High concentration of salt can lead to a build-up of tissue fluid.
Explain how. (2 marks)
1. Higher salt results in lower water potential of
tissue fluid
2. So less water returns to capillary by osmosis at venule end
39
Suggest one advantage to a bacterium secreting a protein (2 marks)
1. To digest protein;
2. So they can absorb amino acids for growth
40
Describe the action of membrane-bound dipeptidases and explain their importance. (2 marks)
1. Hydrolyse peptide bonds to release amino acids;
2. Amino acids can cross cell membrane and dipeptidases cannot
41
Explain three ways in which an insect’s tracheal system is adapted for efficient gas
exchange. (3 marks)
1. Tracheoles have thin walls so short diffusion distance to cells
2. Highly branched tracheoles so short diffusion distance to
cells;
3. Body can be moved by muscles to move air so maintains concentration gradient
42
Why are gills useful for actively seeking prey underwater? (2 marks)
1. higher respiratory rate
2. so uses more oxygen
43
Explain the advantage for larger animals of having a specialised system that facilitates oxygen uptake. (2 marks)
1. Larger cells have smaller surface area to volume ratio;
2. Faster diffusion
44
Mammals such as a mouse and a horse are able to maintain a constant body temperature.
Use your knowledge of surface area to volume ratio to explain the higher metabolic rate of a mouse compared to a horse. (3 marks)
1. Smaller so larger surface area to volume ratio;
2. More heat loss per gram
3. Faster rate of respiration/metabolism releases heat;
45
Suggest one practical advantage of measuring the masses of frog eggs,
tadpoles and adults, compared with measuring their volumes. (1 mark)
More accurate
46
Explain why oxygen uptake is a measure of metabolic rate in organisms. (1 mark)
Oxygen is used in respiration, which is a metabolic process
47
Describe and explain one feature of the alveolar epithelium that makes the
epithelium well adapted as a surface for gas exchange. (2 marks)
1. Single layer of cells
2. Reduces diffusion distance
48
Suggest and explain how a reduced tidal volume affects the exchange of
carbon dioxide between the blood and the alveoli. (3 marks)
1. Less carbon dioxide exhaled
2. So reduced diffusion (between blood and alveoli);
3. Less movement of carbon dioxide out of blood
49
Describe and explain the mechanism that causes lungs to fill with air. (3 marks)
1. Diaphragm muscle contracts and external intercostal muscles
contract;
2. Causes volume increase and pressure decrease;
3. Air moves down a pressure gradient
50
Explain why death of alveolar epithelium cells reduces gas exchange in
human lungs. (3 marks)
1. Reduced surface area;
2. Increased distance for diffusion;
3. Reduced rate of gas exchange;
51
Suggest and explain one way the leaf growth of xerophytic plants would be
different from the leaf growth of sunflowers (2 marks)
1. Low growth;
2. Due to smaller number of stomata for gas exchange
52
Explain why plants
grown in soil with very little water grow only slowly. (2 marks)
1. Stomata close;
2. Less carbon dioxide uptake for less photosynthesis
53
Describe the pathway taken by an oxygen molecule from an alveolus to the blood. (2 marks)
1. Across alveolar epithelium;
2. Endothelium / epithelium of capillary;
54
Explain how one feature of an alveolus allows efficient gas exchange to occur. (2 marks)
1. The alveolar epithelium is one cell thick
2. Creating a short diffusion pathway
55
Explain how changes in the shape of haemoglobin result in the S-shaped oxyhaemoglobin dissociation curve (2 marks)
1. First oxygen binds to haemoglobin causing change in shape
2. Shape change of Hb allows more O2 to bind easier
56
Give three measurements to calculate rate of water movement? (3 marks)
1. Initial and final mass
2. Number of xylem vessels
3. Time taken for water movement
57
Explain why water moves up the stalks of plants? (3 marks)
1. Water evaporates from leaves
2. Lowers water potential and creates tension
3. Hydrogen bonds create tension
58
Describe how to handle a scalpel safely during this procedure. (2 marks)
1. Cut away from body
2. Against flat surface
59
Describe the role of micelles in the absorption of fats into the cells lining the ileum. (3 marks)
1. Micelles include bile salts and fatty acids
2. Make the fatty acids more soluble in water
3. Carries fatty acids to the lining of the ileum
4. Maintain higher concentration of fatty acids to the lining of the ileum
5. Fatty acids absorbed by diffusion;
60
Describe one way this uncontrolled cell division changes the gills (3 marks)
1. thicker filament =
2. increase diffusion distance,
3. so gas exchange would slow down
61
Give two differences between circulation of blood in fish and circulation of blood in a mammal (2 marks)
1. single circulatory system in fish, double in mammal
2. 2 chambers in fish, 4 chambers in mammal
62
In healthy lungs, a gradient is maintained between the concentration of oxygen in the
alveoli and the concentration of oxygen in the lung capillaries.
Describe how ventilation helps to maintain this difference in oxygen concentration. (2 marks)
In alveolus
1. Brings in air containing a higher oxygen concentration;
2. Removes air with a lower oxygen concentration;
63
Name one thing that helps maintain difference in oxygen concentration? (1 mark)
Circulation of blood
64
How do mitochondria help digestion? (2 marks)
1. Site of aerobic respiration
2. Active transport
65
What is the advantage of giving the results as a ratio? (2 marks)
1. Allows comparison
2. Different starting masses
66
An increase in respiration in the tissues of a mammal affects the oxygen dissociation
curve of haemoglobin. Describe and explain how (2 marks)
1. Increase in carbon dioxide;
2. Curve moves to the right
67
Give one way that blood is different from tissue fluid (1 mark)
more proteins
68
The blood pressure decreases along the length of the capillary. What causes this
decrease in pressure? (1 mark)
loss of fluid
69
The zoologist measured oxygen uptake per gram of body mass. Explain why he
measured oxygen uptake per gram of body mass. (2 marks)
1. Enables comparison;
2. As animals differ in size/mass;
70
When a wave of electrical activity reaches the atrioventricular valve, there is a short delay before a
new wave leaves the atrioventricular valve. Explain the importance of this short delay. (2 marks)
1. Allow atria to empty
2. Before ventricles contract;
71
How does training has caused the resting heart
rate of this athlete to be lower. (2 marks)
1. Increase in volume of heart
2. Cardiac output is the same before and after training
3. Increase in stroke volume
72
The haemoglobin in one organism may have a different chemical structure from the
haemoglobin in another organism. Describe how. (1 mark)
different primary structure
73
The maximum pressure in the ventricle is much higher than that in the atrium.
Explain what causes this. (2 marks)
1. Ventricle has)thick wall
2. So contractions are stronger
74
Name two structural features of the gills of a fish that increase their surface area? (1 mark)
1. lots of gill filaments
2. gill filaments covered in lamellae
75
Explain why a bacterium can rely on diffusion for gas exchange, but animals need a transport system (3 marks)
1. animals have a smaller sa:v
2. so diffusion distance larger in animals
3. diffusion rate per unit volume is slower
76
The scale for plotting body mass is a logarithmic scale. Explain why a log scale was used to plot body mass (1 mark)
large/wide range of values
77
Explain how a larger body size is an adaptation to a colder climate (2 marks)
1. smaller sa:v
2. so less heat loss
78
Species of worm that live in ponds cannot live in seawater. Use your knowledge of water potential to explain why (2 marks)
1. lower water potential in seawater
2. water leaves by osmosis and worm dies
79
Explain the movement of oxygen into the gas exchange system of an insect when it is at rest (3 marks)
1) Oxygen used in aerobic respiration
2) so oxygen concentration gradient
3) so oxygen diffuses in
80
What causes the oxygen concentration in the trachea to fall when spiracles are closed? (2 marks)
1. Oxygen is used in respiration in the cells.
2. Oxygen diffuses from the trachea to the cells in tissues.
3. Spiracles are closed so oxygen can't be replaced and can't enter.
81
Suggest a difficulty of counting movements of gill covers as a method of measuring rate of ventilation in fish (1 mark)
movement of gills too fast to count
82
When would a scatter graph not be appropriate? (1 mark)
there are not two dependent variables
83
Describe how the movement of potassium ions into the guard cells causes the stoma to open (4 marks)
1. potassium ions decrease w.p of guard cells
2. water moves into guard cells by osmosis
3. cell swells unevenly so stoma open
4. as inner wall less flexible than outer wall
84
The stomata close when the light is switched off. Explain the advantage of this to the plant (2 marks)
1. preserve water
2. as water lost through the stomata
85
Explain how downward movement of the diaphragm leads to air entering the lungs (2 marks)
1. increased volume of thorax
2. decrease in pressure
3. air moves down pressure gradient
86
Explain in SA:V why large, active organisms need a specialised surface for gas exchange (2 marks)
1. smaller SA:V
2. greater demand for oxygen
3. diffusion distance too large
87
Destruction of phagocytes causes the lungs to be more susceptible to infections. Explain why (2 marks)
1) Phagocytes engulf / ingest pathogens
2) Lung diseases are caused by pathogens
88
The reduced elasticity of the lungs causes breathing difficulty. Explain how. (2 marks)
1) lungs will not inflate / deflate fully / reduced lung capacity;
2)Breathing out no longer passive;
89
Explain two changes in the lungs of people who smoke (2 marks)
1. airways blocked
2. scar tissue
90
The rise of blood glucose is slower with starch than sucrose, why? (3 marks)
1. starch digested to maltose by amylase
2. sucrose digested to glucose by maltase
3. digestion of sucrose is a single step
91
The absorption of galactose from the small intestine is reduced if the absorbing cells are treated with a respiratory inhibitor. Suggest a reason for this (2 marks)
1. no atp formed
2. no active transport of galactose into cells
92
Explain why people with damaged microvilli have low concentrations of amino acids in their blood (2 marks)
1. reduce surface area
2. for absorption
93
Name the part of the pancreatic cell that produces a protease (1 mark)
rough endoplasmic reticulum
94
Suggest the advantage to producing an inactive protease inside cells of the pancreas (2 marks)
1. does not digest proteins inside cells
2. so pancreatic cell not damaged
95
Suggest how the chylomicrons leave the epithelial cell. Give a reason for your answer (2 marks)
1. exocytosis
2. too large
96
Explain the advantages of lipid droplet and micelle formation (3 marks)
1. droplets increase surface area
2. so faster digestion
3. micelles carry fatty acids and monoglycerides to epithelial cell
97
Suggest how the golgi is involved in the absorption of lipids (3 marks)
1. modifies/processes triglycerides
2. combines triglycerides with proteins
3. forms vesicles
98
Why would the concentration of an enzyme not change during an investigation (1 mark)
enzyme not used up
99
How would a curve change if experiment at a lower temp? (1 mark)
curve will be less steep
100
Explain how the shape of a red blood cell allows it to take up a large amount of oxygen in a short time (2 marks)
1. large sa:v
2. for diffusion
101
Explain how oxygen in a rbc is made available for respiration in active tissues (3 marks)
1. low pH due to increased CO2
2. increased disassociation of haemoglobin
3. oxygen diffuses from r.b.c to tissues
102
Explain how aerobic respiration in cells leads to a change in the pH of blood plasma (2 marks)
1. co2 produced
2. hydrogen ions released
103
Explain the advantage for mice living at high altitude in having a dissociation curve which is to the left of the curve for mice living at low altitude (2 marks)
1. high altitudes have low partial pressures of o2
2. high affinity with o2
3. so enough o2 supplied to cells
104
What is meant by partial pressure? (1 mark)
measure of the concentration of a gas
105
List three reasons why large, multicellular organisms need a transport system (3 marks)
1. small sa:v
2. diffusion distance too great
3. to supply enough oxygen
106
What is a single circulatory system? (1 mark)
blood passes through heart one for each circuit
107
What is a closed circulatory system? (1 mark)
blood maintained within vessels
108
The pressure fluctuates as the blood flows along the aorta. Explain what cause this fluctuation (2 marks)
ventricular systole increases pressure
109
State the term used to describe the number of fluctuations per minute (1 mark)
heart rate
110
Explain why it is important that the pressure changes as blood flows from the aorta to the capillaries ( 2 marks)
1. capillary wall only one cell thick
2. high pressure would damage wall
111
Some babies are born with a hole between the right and left ventricles. These babies are unable to get enough oxygen to their tissues. Suggest why (2 marks)
1. blood flows from left ventricle to right ventricle
2. lower volume of oxygenated blood leaves left ventricle
112
The hydrostatic pressure of the blood at the arteriole end of the capillary helps form tissue fluid. Explain how (2 marks)
1. hydrostatic pressure higher than osmotic effect
2. forces water and small molecules out
113
Explain the link between a low concentration of protein in blood plasma and accumulation of tissue fluid (3 marks)
1. water potential in capillary is higher
2. more tissue fluid formed at arteriole end
3. less water absorbed by osmosis into blood capillary
114
Explain how xylem tissue is adapted for its function. (4 marks)
1) Long tubes with no end walls
2) Continuous water columns
3) No cytoplasm/ named organelles to obstruct water flow
4) Lignin to withstand tension in xylem
115
Use your knowledge of the cohesion-tension theory to suggest an explanation for this decrease in trunk diameter (2 marks)
1. adhesion of water molecules to walls of xylem vessel
2. results in tension as water pulled up stem
3. pulling in walls
116
Explain how three features of the plants roots are adaptations to desert conditions. (3 marks)
1. deep roots = deep groundwater
2. shallow roots = rapid uptake of rainfall
3. extensive root systems = maximises water uptake
117
Sorghum has few stomata per mm2 of leaf surface area. Explain how this is an adaptation to the conditions in which sorghum grows. (3 marks)
1. reduced S.A
2. less evaporation of water
3. in dry conditions
118
Suggest two reasons why the rate of water uptake by a plant might not be the same as the rate of transpiration. (2 marks)
1. water used in photosynthesis
2. water produced during respiration
119
Explain one way in which large size is an advantage to blue whales living in cold waters (2 marks)
1. small sa:v ratio
2. loses less heat to water
120
Name the process by which CO2 is removed from a single-celled organism (1 mark)
diffusion over the body surface
121
Explain how the tracheal system limits the size of insects
1. relies on diffusion to bring oxygen to the respiring tissues
2. if insects were large it would take too long for oxygen to reach tissues
122
Fossils have shown insects used to be larger than insects today. What does this suggest about the composition of the atmosphere at the time when fossil insects lived? (1 mark)
it contained more oxygen
123
Water flow over fish gills is one-way whereas the flow of air in and out of the lungs is two-ways. Suggest why one-way flow is an advantage to fish (1 mark)
less energy is required because the flow does not have to be reversed
124
State two similarities between gas exchange in a plant leaf and gas exchange in a terrestrial insect (2 marks)
1. diffuse air through pores on their outer covering
2. need to avoid excessive water loss
125
State two differences between gas exchange in a plant leaf and gas exchange in a terrestrial insect (2 marks)
1. insects do not interchange gases between respiration and photosynthesis - plants do
2. insects have special structures (tracheae) along which gases can diffuse - plants do not
126
Insects limit water loss by having a small sa:v. Why is this not a feasible way of limiting water loss in plants? (1 mark)
plants photosynthesise and therefore need a large surface area to capture light
127
Why can plants that live in cold climates not obtain water from the soil for lots of the year? (1 mark)
water in soil is frozen, cannot be absorbed by osmosis
128
State two reasons why humans need to absorb large volumes of oxygen from the lungs (2 marks)
1. humans are large
2. have a high metabolic rate
129
Explain how cells lining the trachea and bronchus protect the alveoli from damage (3 marks)
1. the cells produce mucus that traps particles of dirt
2. cilia on these cells moves debris up the trachea into stomach
3. dirt could cause damage to alveoli
130
List and explain three organelles that you would expect to be numerous in an epithelial cell of the ileum (3 marks)
1. ER to re-synthesise triglycerides from monoglyceries and fatty acids
2. golgi to form chylomicrons from triglycerides, cholesterol and lipoproteins
3. mitochondria to provide ATP required for the co-transport of glucose and amino acid molecules
131
List four risk factors associated with lung disease (4 marks)
- smoking
- air pollution
- genetic make-up
- occupation
132
Describe how co2 in the air outside a leaf reaches mesophyll cells inside a leaf (3 marks)
1. (Carbon dioxide enters) via stomata;
2. (Stomata opened by) guard cells;
3. Diffuses through air spaces;
4. Down diffusion gradient;
133
Explain how an asthma attach caused a drop in mean FEV (4 marks)
1. Muscle walls of bronchi/bronchioles contract;
2. Walls of bronchi/bronchioles secrete more mucus;
3. Diameter of airways reduced;
4. (Therefore) flow of air reduced;
134
Suggest one reason why Ice fish can survive in seas in Antarctica without haemoglobin (2 marks)
1. temperature low so respiration rate is low so oxygen requirements low
2. rely on oxygen dissolved in water which is adequate
135
State two factors that make it more likely than an organism will have a circulatory pump such as the heart (2 marks)
1. low sa:v
2. high metabolic rate
136
Suggest why it is important to prevent mixing of the blood in the two sides of the heart (3 marks)
1. mixing would result in only partially oxygenated blood reaching tissues and lungs
2. so supply of oxygen to tissues would be inadequate
3. reduced diffusion gradient in lungs so less oxygen uptake
137
Name the chamber of the heart that produces the greatest pressure (1 mark)
left ventricle
138
State one advantage of having thick elastic tissue in the walls of arteries (1 mark)
allows recoil and so maintains blood flow
139
State one advantage of having relatively thick muscle walls in the walls of arterioles (1 mark)
muscle can contract, restricting lumen, so controlling flow of blood into capillaries
140
List the two routes by which tissue fluid returns to the bloodstream (2 marks)
1. capillaries
2. lymphatic system
141
Describe why blood pressure in the aorta fluctuates up and down (1 mark)
elastic layer causes recoil
142
Explain how the rate of blood flow in the capillaries increases the rate of exchange of metabolic materials
1. blood flow is slower
2. allowing more time for metabolic materials to be exchanged
143
If a tree was sprayed with a herbicide that kills living cells, rate of water flow would be unchanged. Why? (2 marks)
1. transpiration pull is a passive process
2. xylem is non-living
144
In a potometer, why is a leafy shoot cut underwater rather than in the air (2 marks)
1. if cut in air then air would be draw into stem, stopping transport of water
2. so cutting underwater means water drawn up, continuous column of water
145
In a potometer, why are all joints sealed with waterproof jelly (2 marks)
1. prevents air being drawn up the xylem and stopping water flow
2. prevents water leaking out
146
State what assumption must be made if a potometer is used to measure the rate of transpiration (1 mark)
that all water taken up is transpired
147
If a potomter is used to compare transpiration rates of two species of plant, what feature of the plants should be kept the same (1 mark)
surface area
148
Suggest reasons why results obtained from a lab potometer experiment may not be representative of the transpiration rate of the same plant in the wild (1 mark)
conditions in lab may be different e.g. more light, greater humidity
149
State two features of a root hair cell that make it specialised in absorbing water and mineral ions (2 marks)
1. thin wall
2. large surface area
150
How are xylem vessels adapted to deal with negative pressure of water being pulled up (1 mark)
thick walls to prevent vessel collapsing
151
Suggest another feature of lignin, other than strength, that make it useful in ensuring water is carried up plant (1 mark)
waterproofing
152
Suggest and explain a difference in a ringing experiment in the summer compared to the winter (2 marks)
1. large swelling above the ring in summer, little swelling in winter
2. summer has higher rate of photosynthesis and so more production of sugars due to increased temp and light intensity
153
Suggest how a branch with a complete ring of phloem removed by squirrels might still survive (1 marks)
leaves can supply sugar needs
154
Why would the sucrose concentration in the phloem in the stem be lower than in the leaves (1 mark)
sucrose in the stem is diluted with water from xylem
155
An arteriole contains muscle fibres. Explain how these muscle fibres reduce blood flow to capillaries (2 marks)
1. (Muscle) contracts;
2. (Arteriole) narrows/constricts/reduces size of lumen/vessel / vasoconstriction;
156
Give an advantage of slow blood flow in capillaries (1 mark)
(More) time for exchange/diffusion (of
substances);
157
Explain why a disease that causes lack of protein in the blood has a build up of tissue fluid (3 marks)
1. Water potential (in capillary) not as low
2. Less/no water removed (into capillary);
3. By osmosis (into capillary);
158
Explain why the values for the pressure in the xylem are negative (1 mark)
(Inside xylem) lower than atmospheric pressure
/ (water is under) tension;
159
The thickness of the aorta wall changes all the time during each cardiac cycle. Explain why (3 marks)
1. (Aorta wall) stretches;
2. Because ventricle
pressure increases (contracts)
3. (Aorta wall) recoils;
4. Because ventricle relaxes, pressure falls;
5. Maintain smooth flow / pressure;
160
How would training impact cardiac output? (2 marks)
1. cardiac output will increase to a higher maximum than before
2. training promotes larger stroke volume
161
Abdominal muscles increases efficiency of gas exchange between the tracheoles and muscle tissue of the insect. Explain why (2 marks)
1. More air/oxygen enters / air/oxygen enters
quickly/quicker;
2. (So) maintains/greater diffusion gradient
162
Explain why small insects don't need abdominal pumping (1 mark)
Large(r) SA:VOL / short(er) diffusion distance
(to tissues);
163
