TOPIC 3A-EXCHANGE AND TRANSPORT SYSTEMS

Question 1

A) In all organisms what substances do they need to take in and excrete from the environment?

Answer 1

A)-cell’s organisms need to take O2 in (aerobic respiration) + nutrients
-they also need to excrete waste products like CO2 + urea

Question 2

B) Outline the main factors that affect organisms with substance exchange with their environment

Answer 2

B)-most organisms need to stay at roughly same temp so heat needs to be exchanged too
-also how easy substance exchange occurs depends on the organism’s SA:V ratio.

Question 3

A) EXAMPLE: A hippo can be represented by a block (2cm x 4cm x 4cm) and a mouse can be represented by a cube (1cm x 1cm x 1cm). Compare their S.A: V ratio.

Answer 3

A) HIPPO: volume= 2x4x4= 32cm3

• its S.A= 2x4x4=32cm2 (top + bottom surfaces of cube)
• -> + 4x2x4=32cm2 (4 sides of cube)
• ->total S.A= 64cm2
• ->so hippo SA: V is 64:32 –> 2:1

MOUSE: volume= 1x1x1= 1cm3

• it’s S.A: is 6x1x1=6cm2
• ->so mouse S.A: V ratio is 6:1

Question 4

B) Therefore what does this comparison of SA:V ratio show?

Answer 4

B)-cube mouse’s S.A is 6 times it’s volume BUT cube hippo’s S.A is only twice it’s volume
–>so smaller animals have a bigger surface area compared to their volume.

Question 5

A) What main substances do all organisms needs to supply every cell with and excrete?

Answer 5

A)-need to supply all cells with substances like glucose and oxygen (for respiration)
-also need to remove waste products from all cells toa avoid damaging itself.

Question 6

B) Describe the exchange of substances in single-celled organisms

Answer 6

B)-the substances can diffuse quickly in or out of cell across cell-surface membrane
–>diffusion rate is quick due to small distances substances have to travel

Question 7

C) Outline and briefly explain the main 2 reasons as to why diffusion of substances across the outer membrane in multicellular organisms is slow

Answer 7

C)1-some cells deep in the body–>means big distance between them and outside environment
2-large animals have low S.A:V ratio–>therefore difficult to exchange enough substances to supply large volume animal through relatively small outer surface.

Question 8

D) Define the term “mass transport”

Answer 8

D)-an efficient system used to carry substances to an from their individual cells.

Question 9

E) What is mass transport referred to in mammals?

F) Therefore, what do multicellular organisms need for substance exchange?

Answer 9

E)-normally refers to circulatory system which uses blood to carry glucose + oxygen around body
–>it also carries hormones/antibodies + waste like CO2
F)-need specialised exchange organs
-also need efficient exchange system to carry substances to and from inidividual cells–>mass transport.

Question 10

G) Describe “mass transport” in plants

Answer 10

G)-involves transport of water and solutes in xylem and phloem.

Question 11

A) How does heat generated from metabolic activity affect an organism and what is it influenced by?

Answer 11

A)-it means organism has to try and remain at it’s right temperature which is pretty heavily influences by an organisms size + shape.

Question 12

B) Explain how the rate of heat loss from an organism depends on it’s S.A (effect of organism’s size)

Answer 12

B)-larger organisms (like hippo) have smaller S.A

• ->makes it harder for it to lose heat from body
• if organism small (e.g: mouse) its relative S.A large so heat lost easier
• ->mean smaller organisms need relatively high metabolic rate to generate enough heat to stay warm.

Question 13

A) Briefly explain how a “compact” and “non-compact” shaped animal affects heat loss

Answer 13

A)-compact: have small S.A relative to volume –>minimising heat loss

• less compact (those that are “gangly”/with “sticking out bits”) have large S.A relative to volume
• ->this increases heat loss from their surface.

Question 14

B) What affects an animal as to whether it’s compact or not?

Answer 14

B)-depends on temperature of animals environment.

Question 15

C) Outline the body temperature and average outside body temperature of the following animals and how their shape affects their S.A:V ratio

Answer 15

C)1-ARCTIC FOX: body temp about 37 degrees C/average outside temp around 0 degrees C
–>small ears + round head to reduce SA:V + heat loss
2-AFRICAN BAT-EARED FOX: body temp 37 degrees C + average outside temp about 25 degrees C
–>big ears + pointier nose to increase S.A:V + heat loss
3-EUROPEAN FOX: body temp 37 degrees C/average outside temp 12 degrees C
–>is intermediate between the 2 foxes to match temp of it’s environment.

Question 16

A) State and explain the following additional adaptations that animals also have for the following problems they experience in their environment:

1-High S.A:V animals tend to lose more water
2-To support high metabolic rates
3-samller mammals
4-Larger organism in hot regions trying to stay cool (e.g: elephants/hippos)

Answer 16

A)1-lose more water as it evaporates from their surface
–>some small desert animals have kidney structure adaptions so produce less urine to compensate
2-so small mammals living in cold regions need to eat lots of high energy foods like seeds/nuts
3-these may have thick fur layers/hibernate when weather gets v. cold
4-elephants developed large flat ears to increase their S.A so can lose heat more
-hippos spend much of day in water–>a behavioural adaptation to help them lose heat.

Question 17

A) What 3 main features do most gas exchange surfaces have in common and so outline their overall effect

Answer 17

A)1-have large S.A
2-they’re thin (often 1 layer of epithelial cells)
–>this provides short diffusion pathway across exchange surface
3-organism also maintains steep concentration gradient of gases across exchange surface

-all of these features have overall effect of increasing diffusion rate.

Question 18

B) How do single-celled organisms exchange substances with their environment and what features do they have to aid this process?

Answer 18

B)-they absorb and release gases by diffusion through their outer surface

• features: relatively large S.A + thin surface + short diffusion pathway (oxygen can’t take part in biochemical reactions as soon as diffuses out of cell)
• ->so no need for gas exchange system.

Question 19

A) Why do fish have special adaptations to get enough oxygen?

Answer 19

A)-there is low concentration of oxygen in water than air

Question 20

B) Describe how the gills of a fish are adapted to acquire the maximum amount of oxygen from the water (reference to diagram of gill)

Answer 20

B)1-each gill made of lots of thin plates–>gill filaments
–>these give large S.A for gas exchange
2-gill filaments covered in lots of tiny structures called lamellae
–>these increase S.A even more
-lamellae have lots blood capillaries + thin surface layer of cells to speed diffusion up

Question 21

C) Explain the counter-current flow system in fish

Answer 21

C)-blood flow through lamellae in one direction while water flows over in opposite direction–>counter-current flow system

• ->this maintains concentration gradient between water and blood
• ->concentration of oxygen always higher in water than blood so max O2 diffuses from water in to blood.

Question 22

A) Outline the structure used by insects in their body for gas exchange

Answer 22

A)-insects have microscopic air-filled pipes called trachea which used for gas exchange.

Question 23

B) Step-by-step describe the gas exchange in insects from taking oxygen in and getting rid of CO2

Answer 23

B)-air moves into trachea via pores on surface called spiracles

• ->O2 travels down conc gradient towards cells
• ->trachea branch off in to smaller tracheoles that have thin permeable walls and go to individual cells
• ->this means O2 diffuses directly in to respiring cells (means insect’s circulatory system not transport O2)
• CO2 from cells moves down it’s own conc gradient towards spiracles to be released in to atmosphere
• insects use rhythmic abdominal movements to move air in and out of the spiracles.

Question 24

A) Describe the involvement of the main two gases O2 and CO2 in plants

B) What is the main gas exchange surface in the leaf?

Answer 24

A)-plants need CO2 for photosynthesis which produces O2 as “waste” gas
–>they need O2 for respiration which produces CO2 as waste gas.
B)-it’s the surface of the mesophyll cells in the leaf.

Question 25

C) Explain how this gas exchange surface is adapted for efficient gas exchange

D) What controls the opening and closing of stomata?

Answer 25

C)-well adapted as have large S.A
-mesophyll cells are inside leaf
–>gases move in + out through special pores in epidermis called stomata (singular=stomata)
-stomata can open to allow exchange of gases
–>and close if plant losing too much water
D)-guard cells.

Question 26

A) What is the side effect of gas exchange in plants and insects?

B) Consequently how do plants and insects respond to this problem?

Answer 26

A)-tends to make them lose water–>sort of trade-off between the 2
B)-luckily plants + insects have evolved adaptations to minimise water loss without reducing gas exchange too much.

Question 27

C) How are insects adapted to reduce water loss?

Answer 27

C)-they close their spiracles using muscles

• ->also have waterproof waxy cuticle all over their body
• ->and have tiny hairs around spiracles
• ->these 2 adaptations both reduce evaporation.

Question 28

D) In appropriate detail explain how plants are adapted to reduce water loss during gas exchange

Answer 28

D)-plant’s stomata usually kept open during day to allow gaseous exchange

• ->water enters guard cells making them turgid which opens stomatal pore
• ->if plant starts to get dehydrated guard cells lose water and become flaccid which closes pore.

Question 29

E) Describe “xerophytes”

Answer 29

E)-these are plants that are specially adapted fro life in warm, dry or windy habitats where water loss a problem.

Question 30

F) Briefly explain the following adaptations of xerophytes:

1-Stomata sunken in pits 
2-Layers of "hairs" on epidermis 
3-Curled leaves with stomata inside 
4-Reduced n. of stomata 
5-Waxy, waterproof cuticles

Answer 30

F)1-these trap moist air–>reduces conc. gradient of water between leaf and air
–>reduces amount of water diffusing out of leaf and evaporating
2-again these too trap moist air round stomata
3-protecting them from wind (windy conditions increase diffusion + evaporation rate)
4-so there are fewer places for water to escape
5-these found on leaves and stems–>reduce evaporation.

Question 31

A) When does VENTILATION and the GAS EXCHANGE SYSTEM come in to action in humans?

Answer 31

A)-comes in to action when humans need to get O2 into blood (for respiration) and get rid of CO2 (made by respiring cells)

Question 32

B) Outline how the breathing system splits down further and further in humans when air is breathed in

Answer 32

B)1-as breathe in air enters trachea (windpipe)

• ->trachea splits to 2 bronchi–>1 bronchus leading to each lung
• ->each bronchus branches off into smaller tubes-bronchioles
• ->bronchioles end in small “air sacs” called alveolus
• ->gas exchanged here.

Question 33

C) State the 3 parts of the gas exchange system that work together to move air in and out

Answer 33

C)-ribcage/intercostal muscles and diaphragm.

Question 34

A) What does ventilation consist of?

B) What is ventilation controlled by?

Answer 34

A)-inspiration (breathing in) and expiration (breathing out).
B)-controlled by movements of diaphragm/internal and external intercostal muscles + ribcage.

Question 35

C) Briefly explain the process of inspiration step-by-step

Answer 35

C)1-external intercostal + diaphragm muscles contract
2-this causes ribcage to move up + out and diaphragm flattens
–>increases thoracic cavity volume (space where lungs are)
3-as thoracic volume increases–>lung pressure decreases (to below atmospheric pressure)
4-air will always flow from high to low pressure area (i.e: down a pressure gradient)
–>so air flows down trachea into lungs

Question 36

D) What type of process is “inspiration”?

Answer 36

D)-active process–> needs energy.

Question 37

E) Describe step-by-step the process of “expiration”

F) Outline the type of process that normal expiration is

Answer 37

E)1-external intercostal + diaphragm muscles relax
2-ribcage moves down + in and diaphragm becomes curved again
3-thoracic volume decreases–>causes pressure to increase (to above atmospheric pressure)
4-air forced down pressure gradient and out of lungs F)-passive process–>not need energy

Question 38

G) How does “forced expiration” work?

Answer 38

G)-during forced expiration external intercostal muscles relax AND internal intercostal muscles contract

• ->pulling ribcage further down + in
• ->during this time movement of the 2 sets of intercostal muscles said to be antagonistic (opposing).

Question 39

A) Describe “alveoli”

B) What is each alveolus made from?

Answer 39

A)-lungs contain millions of these microscopic air sacs where gas exchange occurs
B)-each one made from single layer of thin, flat cells called alveolar epithelium.

Question 40

A) Outline the effect of there being lots of alveoli in the lungs

B) What are the alveoli surrounded by?

Answer 40

A)-means there is big S.A for exchanging O2 and CO2

B)-surrounded by network of capillaries.

Question 41

C) Describe the gas exchange of O2 and CO2 at the alveoli

Answer 41

C)-O2 diffuses out of alveoli across alveolar epithelium and capillary endothelium (type of epithelium that fomrs the capillary wall)

• ->and into haemoglobin in blood
• CO2 diffuses into alveoli from blood and breathed out.

Question 42

D) Give a summary on the movement of air through the gas exchange system and in particular the diffusion of oxygen in to the blood capillaries

Answer 42

D)-O2 from air moves down trachea, bronchi and bronchioles into alveoli

• ->this movement happens down a pressure gradient
• ->once in alveoli O2 diffuses across alveolar epithelium, then capillary endothelium–>ends up in capillary itself
• ->this movement occurs down a diffusion gradient.

Question 43

A) Describe how the following features of the alveoli speed up the rate of diffusion so that gas exchange can occur quickly:

1-thin exchange surface
2-large S.A
3-steep conc gradient

Answer 43

A)1-the alveolar epithelium only 1 cell thick
–>means diffusion pathway short (speeds diffusion up)
2-large n. of alveoli means means S.A large for gas exchange
3-steep conc gradient of O2 and CO2 between alveoli and capillaries–>increases diffusion rate
–>this constantly maintained by blood flow and ventilation.

Question 44

A) What does “lung disease” affect?

B) How do doctors diagnose lung disease?

Answer 44

A)-affects both ventilation (breathing) and gas exchange in lungs–>how well lungs function
B)-by carrying out tests

Question 45

C) Define and describe the following key terms:

1-Tidal Volume
2-Ventilation Rate
3-Forced Expiratory Volume (FEV1)
4-Forced Vital Capacity (FVC)

Answer 45

A)1-its the volume of air in each breath–>usually between 0.4 dm3-0.5dm3 for adults
2-is n. of breaths per min–>for healthy person it’s around 15 breaths
3-it is the maximum volume of air that can be breathed out in 1 sec
4-is the maximum volume of air possible to breathe out forcefully from lungs after v. deep breath.

Question 46

D) With reference to the graph (example) show how tidal volume/ventilation rate and other breathing measures could be determined

Answer 46

D)-sharp peak shows deep breath

• ->peak then back down below 2 shows deep breath out
• tidal volume of normal breath shown between 2 dashed lines

Question 47

PULMONARY TUBERCULOSIS (TB):

A) Describe how ones gaseous exchange surface is damaged when they become infected with tuberculosis bacteria

B) Consequently, what is the effect of the gaseous exchange surface becoming damaged?

Answer 47

A) -the immune system builds a wall around bacteria in lungs
–>this forms small + hard lumps known as tubercles
–>infected tissue within the tubercles dies and gaseous exchange surface damaged.
B)-tidal volume is decreased

Question 48

C) What does TB also causes and what is the effect?

Answer 48

C)-tuberculosis causes fibrosis–>further reduces tidal volume

Question 49

A) Describe the formation of fibrosis and what causes it

Answer 49

D)-fibrosis is formation of scar tissue in lungs

• ->could be due to infection OR exposure to substances like abestos/dust
• ->the scar tissue is thicker + less elastic than normal lung tissue.

Question 50

B) Therefore, why is TIDAL VOLUME and FVC reduced as a result of fibrosis?

Answer 50

E)-means lungs less able to expand so unable to hold as much air as normal

• ->so tidal volume and FVC reduced
• ->i.e: smaller volume of air can be breathed out forcefully)

Question 51

C) Why is there a reduction in the rate of gaseous exchange from fibrosis?

D) Outline the symptoms off fibrosis

Answer 51

C)-this is as diffusion is slower across a thicker scarred membrane
D)-shortness of breath/dry cough/chest pains/fatigue + weakness

Question 52

E) Briefly explain why fibrosis sufferers have a faster ventilation rate than normal

Answer 52

E)-to get enough air into their lungs to oxygenate their blood.

Question 53

A) Describe the lung diseases “asthma”

Answer 53

A)-its a respiratory condition where airways become inflamed + irritated
–>causes vary from case to case but usually due to allergic reaction to substances like pollen and dust

Question 54

B) Explain what occurs during an “asthma attack” and how it leads to the serious reduction of FEV1

Answer 54

B)-from asthma attack smooth lining of broncholes contracts + lots of mucus produced

• ->causes constriction of airways so difficult for sufferer to breath properly
• ->air flow in + out of lungs severely reduced
• ->so less O2 enters alveoli and moves to blood
• ->reduced airflow means FEV1 seriously reduced
• ->i.e less air can be breathed out per second.

Question 55

C) What is “emphysema” and what causes it?

Answer 55

C)-is lung disease caused by smoking OR long-term air pollution exposure
–>foreign particles in smoke (or air) become trapped in alveoli

Question 56

D) Outline how emphysema affects elastin

Answer 56

D)-causes inflammation which attracts phagocytes to the area
–>phagocytes produce an enzyme that breaks elastin (protein found in alveoli cell walls) down

Question 57

E) How does the loss of elastin cause problems?

Answer 57

E)-elastin is elastic–>helps alveoli return to their normal shape after inhaling/exhaling air

• ->loss of elastin means alveoli can’t recoil t expel air as well (remains trapped in alveoli)
• loss of elastin also leads to destruction of alveoli walls
• ->this reduces S.A of alveoli–>so rate of gaseous exchange decreases.

Question 58

F) What are the symptoms of emphysema?

Answer 58

F)-shortness of breath + wheezing
–>people with emphysema have increased ventilation rate as they try to increase amount of air (with oxygen) reaching lungs.

Question 59

A) How do all the diseases described above often make sufferers feel tired and weak?

Answer 59

A)-TB/fibrosis/asthma + emphysema all reduce gas exchange rate in alveoli

• ->less O2 able to diffuse into blood stream–>so body cells receive less O2–>so aerobic respiration rate reduced
• ->means less energy released
• ->so sufferers often feel tiered + weak.

Question 60

A) What are “risk factors” in terms of diseases and outline an example

Answer 60

A)-all diseases have factors that increase one’s chance of getting the disease

• E.G: widely known if smoke then more likely to get lung cancer
• ->smoking is risk factor for lung cancer.

Question 61

B) Describe what it means by “correlation” and how it’s normally misinterpreted

Answer 61

B)-it’s a link between 2 things

• normally misinterpreted that correlation is cause of disease BUT it isn’t
• ->E.G: smokers have increased chance of getting cancer but not necessarily mean smoking causes disease
• ->lot’s of other factors to consider.

Question 62

EXAMPLE 1: Smoking and lung cancer
Study the 2 graphs in detail:

A) Describe the data shown

Answer 62

A)-graph on left shows that n. of adult males in GB who smoke decreased between 1990-2012
-graph on right shows that male lung cancer mortality (death) rate decreased between 1990-2012 in U.K.

Question 63

B) From the data provided what conclusions may be drawn?

Answer 63

B)-there is correlation between n. of males who smoke and mortality rate for male lung cancer

• ->BUT can’t say one caused other as could be other reasons for trend like death from lung cancer may have decreased as less asbestos being used in homes
• ->not due to less smoking.

Question 64

C) Outline the other points that needs to be considered when evaluating this data (in terms of this example)

Answer 64

C)-graph on right shows mortality (death) rates

• ->lung cancer cases rate may of been increasing BUT medical advances may mean more surviving
• ->so only mortality was decreasing.

Question 65

D) You also need to evaluate the way in which scientific data has led to government restrictions on risk factor sources:

Medical studies in the 1950’s and ‘60’s documented the link between smoking and various forms of cancer, particularly lung cancer. What did this evidence prompt the government to do?

Answer 65

D)-prompted first voluntary agreement between government and tobacco companies in 1971

• ->it stated tobacco products + adverts should carry health warning label
• ->as of OCT 2008 picture health warnings made compulsory on all U.K cigarette boxes after studies suggested they more effective than written warnings alone.

Question 66

EXAMPLE 2: AIR POLLUTION AND ASTHMA (with reference to attached graph)

A) State the information that the 2 graphs provide

Answer 66

A)-top graph shows n.of asthma cases per 100, 000 of population diagnosed in U.K 1996-2000
-bottom graph shows emissions (millions of tonnes) of sulfur dioxide (of air pollutant) from 1996-2000 in U.K.

Question 67

B) Describe the data shown by the 2 graphs

Answer 67

B)-top graph shows that n.of new asthma cases in U.K fell from 1996-2000 at 87% to 62% per 100,000 people
-bottom graph: shows emissions of sulfur dioxide in U.K fell from 2 to 1.2 million tonnes from 1996-2000.

Question 68

C) What conclusions may be drawn from the data?

Answer 68

C)1-link between n.of new asthma cases and SO2 emissions in U.K

• ->rate of new asthma cases fallen as SO2 emissions fallen
• ->can’t say one causes other as could be other reasons for trend
• ->E.G: n. of new asthma cases could be falling due to decrease in n. of people smoking
• can’t say asthma cases reduction linked to reduction in pollution (general) either as only SO2 levels studied.

Question 69

D) When evaluating this data what other points would need to be considered?

Answer 69

D)-top graph shows new asthma cases

• ->rate of new cases may be decreasing but existing cases becoming more severe
• emissions were for whole of U.K but air pollution varies area to area–>E.G: cities tend to be more polluted
• asthma data doesn’t take any other factors into account that may increase risk of developing asthma
• ->E.G: allergies/smoking etc.