3A - Exchange And Transpor Systems Flashcards
Name 5 things an organism needs to exchange with its environment.
- Oxygen
- Nutrients
- Carbon dioxide
- Urea
- Heat
How does the shape and size of an organism affect the rate of substance exchange?
The higher the surface area to volume ratio, the faster the rate of gas exchange.
Compare the surface area to volume ratio of a mouse and a hippo.
- Mouse -> Large SA:V ratio
* Hippo -> Small SA:V ratio
What are the 3 categories of exchange substances in an organism?
- Supply reactants (e.g. glucose)
- Waste products (e.g. urea)
- Heat
Compare and explain gas exchange systems in single-called and multicellular organisms.
- Single-celled -> Diffuse through the cell membrane -> Short distance for diffusion
- Multicellular -> Require exchange organs and mass transport systems -> Diffusion through surface is too slow
Why can’t multicellular animals exchange substances through their surface?
- Some cells are deep within the body -> Big distance between them and the surface
- Small SA:V ratio -> Diffusion is too slow
Instead of exchanging substances through their surface, what do multicellular animals do?
They have specialised exchange organs and mass transport systems.
What is a mass transport system?
A system that carries substances to and from individual cells.
Describe mass transport in mammals.
The circulatory system carries in blood: • Glucose • Oxygen • Hormones • Antibodies • Waste (e.g. CO2)
Describe mass transport in plants.
The xylem and phloem carry:
• Water
• Solutes
Describe the effect of being a large animal on heat loss and how large animals deal with this in a hot environment.
Large size -> Small SA:V ratio -> Difficult to lose heat -> Have a less compact shape (e.g. large ears) to lose heat + Low metabolic rate
Describe the effect of being a small animal on heat loss and how small animals deal with this in a cool environment.
Small size -> Large SA:V ratio -> Easily lose heat -> Have a more compact shape (e.g. small ears) to lose less heat + High metabolic rate
What two factors of an organism’s physique affect heat loss?
- Size
* Shape
Compare the metabolic rate of small and large animals in the same environment.
- Small -> High metabolic rate
* Large -> Low metabolic rate
Compare the shape of small and large animals in the same environment.
- Small -> Compact shape (e.g. small ears)
* Large -> Less compact shape (e.g. large ears)
Give some examples of adaptations of animals in hot regions.
- Small animals produce less urine -> Compensate for high levels of water loss through surface
- Large animals may have large ears (e.g. elephants)
- Large animals may spend time in water (e.g. hippos)
Give some examples of adaptations of animals in cold regions.
- Small mammals eats high energy foods, such as nuts and seeds -> Support the high metabolic rates
- Small mammals have thick fur
- Small mammals may hibernate
What are the three types of adaptation?
- Structural / Physical
- Behavioural
- Physiological
What is a structural/physical adaptation?
A feature of an organism’s body that helps it survive.
What is a behavioural adaptation?
A response or behaviour of an organism that helps it survive.
What is a physiological adaptation?
A body process that helps an organism survive.
What 3 features are common to all exchange surfaces?
1) Large surface area
2) Thin
3) Steep concentration gradient
How does the thickness of an exchange surface affect the rate of diffusion across it?
The thinner it is, the shorter the diffusion pathway, which increases the rate of gas exchange.
How thick are most gas exchange surfaces?
Often only 1 cell thick.
How does the oxygen concentration in water and air compare? What is the consequence of this?
It is lower in water -> Fish must have a special system to absorb sufficient oxygen.
What is the system of maximising gas exchange in fish called?
Counter-current system
Describe the counter-current system in fish.
1) Water enters through the mouth and out through the gills.
2) Each gill is made of thin plates called gill filaments, which are covered in tiny bumps called lamellae
3) Lamellae have a thin surface and lots of blood capillaries
4) Blood flows between lamellae in the opposite direction to the blood
5) This maintains a steep oxygen concentration gradient at all points along the gill so that diffusion is maximised
Describe how gills are adapted for gas exchange.
- Gill filaments + lamellae increase SA
- Good blood supply to lamellae maintain concentration gradient
- Lamellae have thin walls for short diffusion distance
- Counter-current flow maintains a concentration gradient at all points along the gill
What are lamellae?
Small bumps on gill filaments that increase SA.
Describe the structure of a gill.
- Central gill arch, containing arteries
- Gill filaments branch off from gill arch
- Lamellae on gill filaments
- Gill rakers on opposite side of gill arch
Describe how water passes through lamellae.
If the lamellae are arranged along the filament like…
| | | | | | |
Then the water will flow vertically, in the opposite direction to the blood.
Describe the graph pf oxygen concentration (y) against distance along the gill plate (x).
• “Blood” arrow from bottom right to top left
• “Water” arrow from top left to bottom right
(See diagram pg 56)
Remember to revise gas exchange in fish.
See pg 56 of revision guide.
Describe the system of gas exchange in insects.
1) Air moves into the insect through spiracles and into the tracheae.
2) Oxygen travels down the tracheae along the concentration gradient.
3) Tracheae branch off into tracheoles, which have thin walls and reach every cell.
4) CO2 moves the opposite way, along its own concentration gradient.
5) Air is moved in and out of the spiracles by rhythmic abdominal movements.
Describe the path of oxygen as it moves into an insect.
Spiracles -> Tracheae -> Tracheoles -> Cells
Does an insect’s circulatory system transport oxygen?
No, it all happens through the tracheae and tracheoles.
How does an insect make air move in and out of the spiracles?
Rhythmic abdominal movements.
What are spiracles?
Pores on the surface of an insect for gas exchange.
Which gases are needed in a plant and which waste gases does this produce?
- Photosynthesis -> Needs: CO2, Waste: O2
* Respiration -> Needs: O2, Waste: CO2
Where does gas exchange happen in a plant?
Surface of the mesophyll cells in the leaf.
Describe gas exchange in plants.
- Gases diffuse in and out of the plant through stomata
* These then move in and out of mesophyll tissue inside the leaf
Describe the structure of a leaf from top to bottom.
- Waxy cuticle
- Upper epidermis
- Palisade mesophyll
- Spongy mesophyll
- Lower epidermis -> Guard cells + Stomata
- Waxy cuticle
What are stomata?
Pores in the lower epidermis of a leaf that allow gas and water exchange.
What is the compromise in gas exchange in plants and insects?
If the stomata/spiracles remain open for gas exchange, too much water can be lost through the stomata.
How do insects deal with the gas exchange - water loss compromise?
- If too much water is lost, spiracles are closed by muscles
* Have a waxy cuticle + Hairs -> Reduces evaporation
How do plants deal with the gas exchange - water loss compromise?
- Stomatal rhythm -> Stomata open during the day and close during the night (when photosynthesis can’t happen)
- Guard cells become turgid or flaccid to open or close stomata -> Close stomata when dehydrated
How do insects open and close their spiracles?
Using muscles.
How do plants open and close their spiracles?
- When the plant is hydrated -> Guard cells become turgid -> Opens the stomata
- When the plant is dehydrated -> Guard cells become flaccid -> Closes the stomata
What are xerophytes?
Plants adapted to warm, dry or windy habitats where water loss is a problem.
Give some examples of xerophyte adaptations.
- Stomata sunk in pits -> Trap moist air, reducing the water concentration gradient
- Hairs on the epidermis -> Trap moisture around the stomata
- Curled leaves with stomata inside -> Protect stomata from wind
- Reduced number of stomata
- Waxy waterproof cuticles -> Reduce evaporation
In humans, what are the specialised gas exchange organs?
Lungs
Describe the path of oxygen entering the human body.
Trachea -> Bronchi -> Bronchioles -> Alveoli
How many types of intercostal muscles are there in the human ribcage?
- External
* Internal
What is ventilation?
Breathing in (inspiration) and breathing out (expiration).
Describe the process of inspiration.
1) External intercostal muscles contract (and internal intercostal muscles relax) -> Ribcage moves out
2) Diaphragm contracts -> Flattens
3) Thorax volume is increased -> Lung air pressure decreases
4) Air flows into the lungs down a pressure gradient
5) This is an ACTIVE process (requires energy).
Describe the process of expiration.
1) External intercostal muscles relax (and internal intercostal muscles contract) -> Ribcage moves in
2) Diaphragm relaxes -> Becomes dome shaped
3) Thorax volume is decreased -> Lung air pressure increases
4) Air flows out of the lungs down a pressure gradient
5) This is a PASSIVE process (no energy required).
Compare the processes of inspiration and expiration in terms of energy use.
- Inspiration -> Always active
* Expiration -> Passive, unless forced expiration
What are the two types of expiration?
- Normal expiration -> No internal intercostal muscles involved -> Passive process
- Forced expiration -> Internal intercostal muscles involved -> Active process
Describe the movement of intercostal muscles in forced expiration.
Antagonistic (opposing) -> Internal muscles contract, external muscles relax
What are alveoli?
Microscopic air sacs in the lungs where gas exchange happens.
What is an alveolus made from?
- A single layer of thin, flat cells
* Called the alveolar epithelium
Describe gas exchange in the alveoli.
- Oxygen diffuses from the alveoli, across the alveolar epithelium and then the capillary endothelium, into the capillary -> Down a concentration gradient
- CO2 diffuses from the capillary, across the capillary endothelium and across the alveolar epithelium, into the alveoli -> Down a concentration gradient
What is the wall of the alveolus called?
Alveolar epithelium
What is the wall of a capillary in contact with an alveolus called?
Capillary endothelium
Give 3 adaptations of alveoli for gas exchange.
1) Thin exchange surface -> Alveolar epithelium is only one cell thick -> Short diffusion distance
2) Large SA -> Large number of alveoli
3) Constant blood supply + ventilation -> Maintains steep concentration gradient
What two things can lung disease affect?
- Ventilation
* Gas exchange
What tests can be used to diagnose lung diseases?
- Tidal volume
- Ventilation rate
- Forced expiratory volume
- Forced vital capacity
What is tidal volume?
The volume of air in each breath.
What is a typical tidal volume for adults?
0.4 - 0.5 dm3
What is ventilation rate?
The number of breaths per minute.
What is a typical ventilation rate for adults?
15 breaths per minute.
What does FEV1 stand for?
Forced Expiratory Volume
What is forced expiratory volume?
The maximum volume of air that can be breathed out in 1 second.
What does FVC stand for?
Forced vital capacity
What is forced vital capacity?
The maximum volume of air it is possible to breathe forcefully out of the lungs after a deep breath in.
What device can be used to measure breathing results (e.g. ventilation rate)?
Spirometer
What is a spirometer?
A device used to measure the volume of air breathed in and out.
On a graph of volume of air in lungs (y) against time (x), why does the volume never reach 0dm3?
There is residual air in the lungs.
Remember to practice labelling a spirometer graph.
See graph of 60 of revision guide.
Name 4 lung diseases.
- Pulmonary Tuberculosis (TB)
- Fibrosis
- Asthma
- Emphysema
What is residual air in lungs?
The air that cannot be expelled in an breath out.
Describe pulmonary tuberculosis (TB) in terms of:
• Causes
• Effects
• Symptoms
1) Tuberculosis bacteria infect a person.
2) Immune system cells build a wall around the bacteria in the lungs -> Forms lumps called tubercles -> Tissue dies
3) Surface is damaged -> Tidal volume is reduced.
4) Fibrosis also occurs -> Tidal volume + FVC are reduced.
5) Ventilation rate is increased.
6) Symptoms: Cough, Coughing up blood and mucus, Chest pains, Shortness of breath, Fatigue
Describe the symptoms of pulmonary tuberculosis (TB).
- Cough
- Coughing up blood and mucus
- Chest pains
- Shortness of breath
- Fatigue
Describe fibrosis in terms of:
• Causes
• Effects
• Symptoms
1) Fibrosis is the formation of scar tissue in the lungs.
2) Due to infection or exposure to asbestos or dust.
3) Scar tissue is inelastic -> Tidal volume and FVC are reduced.
4) Scar tissue is thicker -> Slower diffusion.
5) Ventilation rate is increased.
6) Symptoms: Shortness of breath, Dry cough, Chest pain, Fatigue, Weakness
Describe the symptoms of fibrosis.
- Shortness of breath
- Dry cough
- Chest pain
- Fatigue
- Weakness
Describe asthma in terms of:
• Causes
• Effects
• Symptoms
1) Allergic reaction to pollen or dust.
2) Causes airways to become inflamed and irritated.
3) During attack, smooth lining of bronchioles contracts + mucus is produced -> Airways are constricted.
4) Air flow is reduced -> FEV1 is reduced
5) Symptoms: Wheezing, Tight Chest, Shortness of breath
Describe the symptoms of asthma.
- Wheezing
- Tight chest
- Shortness of breath
How can the symptoms of an asthma attack be alleviated?
Using drugs, such as those in inhalers, to relax the bronchiole muscles.
Describe emphysema in terms of:
• Causes
• Effects
• Symptoms
1) Smoking or long-term exposure to air pollution
2) Foreign particles are trapped in the alveoli -> Inflammation
3) Phagocytes are attracted to area -> Produce an enzyme that breaks down elastin (a protein in alveoli walls)
4) This makes the alveoli less elastic -> Tidal volume and FVC reduced
5) Destruction of alveoli walls -> Rate of gas exchange reduced
6) This causes an increased ventilation rate
7) Symptoms -> Shortness of breath, Wheezing
Describe the symptoms of emphysema.
- Shortness of breath
* Wheezing
Give the causes of: • Pulmonary tuberculosis • Fibrosis • Asthma • Emphysema
- Pulmonary tuberculosis -> Tuberculosis bacteria infection
- Fibrosis -> Infection or exposure to asbestos or dust
- Asthma -> Irritation due to allergens
- Emphysema -> Smoking or air pollution
Give the effect on measures of lung function of: • Pulmonary tuberculosis • Fibrosis • Asthma • Emphysema
- Pulmonary tuberculosis -> Reduced tidal volume + FVC
- Fibrosis -> Reduced tidal volume + FVC
- Asthma -> Reduced FEV1
- Emphysema -> Reduced tidal volume + FVC
What do the 4 main lung diseases have in common?
They all reduce the rate of gas exchange -> Less oxygen can diffuse into the blood -> Aerobic respiration is reduced -> Sufferers feel tired and weak
What are risk factors of a disease?
Factors that will increase a person’s chance of getting that disease.
When given graphs (on pg 62) and asked to describe the relationship between the percentage population smoking and deaths from lung cancer, can you claim that smoking causes lung cancer?
No, because there is a correlation between the decrease in smoking and the decrease in deaths, but there could be OTHER factors that caused the decrease.
What two things could you be asked to do when presented with lung disease data graphs?
1) Describe the data
2) Draw conclusions (e.g. correlations)
Describe the graphs on pg 62 of the revision guide.
- The number of adult males in Great Britain who smoke decreased between 1990 and 2012.
- Make lung cancer mortality rate decreased between 1990 and 2012 in the UK.
Draw conclusions from the graphs on pg 62 of the revision guide.
- Correlation between the number of males who smoked and the morality rate for male lung cancer.
- But this doesn’t necessarily suggest causation -> There may have been other reasons for the trend.
What other points might you consider with the graphs on pg 62 of the revision guide?
The graph on the right shows mortality rates. It’s possible that the rate of cases of lung cancer could be increasing, but medical advances mean more people were surviving.
Describe how scientific data about the hazards of smoking have led to government restrictions.
- Medical studies in 1950s and 1960s documented the link between smoking and various forms of cancer, particularly lung cancer.
- This prompted the first voluntary agreement between the UK government and tobacco companies in 1971 -> Tobacco products and warnings must carry a health warning
- In 2008, picture health warnings were made compulsory on all UK boxes of cigarettes -> Studies showed they were more effective than written warnings alone
Describe the graphs on pg 63 of the revision guide.
- Number of new cases of asthma in the UK fell between 1996 and 2000, from 87 to 62 per 100,000 people.
- Emissions of sulphur dioxide in the UK fell between 1996 and 2000, from 2 to 1.2 million tonnes.
Draw conclusions from the graphs on pg 63 of the revision guide.
- Correlation between sulphur dioxide emissions and number of new cases of asthma.
- But this doesn’t necessarily suggest causation -> There may be different reasons for the trend.
Suggest an alternative explanation for the decreasing mortality rates for male lung cancer in the UK on pg 62, rather than a decrease in smoking.
There may have been less asbestos used in homes.
Suggest an alternative explanation for the decreasing number of new cases of asthma in the UK on pg 63, rather than a decrease in sulphur dioxide emissions.
There may have been a decrease in the number of people smoking.
Looking at the graphs on pg 63, comment on how pollution affects the number of cases of asthma.
You can’t comment on pollution in general, since on sulphur dioxide levels were studied.
What other points might you consider with the graphs on pg 63 of the revision guide?
- Top graph shows new cases of asthma -> Existing cases could be becoming more severe.
- Emissions are for the whole UK, but pollution varies from place to place.
- Asthma data doesn’t take into account other factors that may increase the risk of developing asthma (e.g. allergies)
Describe how scientific data about the dangers of air pollution have led to government restrictions.
- Studies connected air pollution to various diseases.
- EU adopted the National Emissions Ceilings Directive -> Set upper limits on the total emissions of 4 major pollutants in the atmosphere, to be achieved by 2010 -> New limits for 2020 are being agreed.
- EU also introduced the Clean Power for Transport Package to promote cleaner fuels for vehicles
- UK taxes car owners according to their car’s emissions
Describe two risk factors of lung diseases that are being restricted by the government.
- Smoking
* Air pollution
Describe how you can dissect lungs.
1) Wear a lab coat and ensure that dissection tools are sharp, clean and free from rust.
2) Place sheep or pig lungs on cutting board.
3) Attach piece of rubber tubing to the trachea and inflate by pumping in air using a foot pump.
4) Use scissors or scalpel to cut vertically down the trachea along the gap in the C-shaped cartilage rings.
5) Continue cutting down one of the bronchi + observe bronchioles.
6) Cut off a piece of lung -> It is spongy because of trapped air.
7) Wash your hands and disinfect surfaces.
(See diagram pg 64 of revision guide)
Explain the condition that tools need to be in for dissection.
• Clean
• Sharp
• Free from rust
Because blunt tools don’t cut well and can be dangerous.
Describe a cross-section of a trachea.
- C-shaped cartilage makes up most of circumference
- Smooth muscle makes up remainder
(See diagram pg 64 of revision guide)
Why does a piece of lung feel spongy?
Air is trapped in the alveoli
Describe how you can dissect fish gills in bony fish.
1) Wear a lab coat and ensure that dissection tools are sharp, clean and free from rust.
2) Place fish in dissection tray or on cutting board.
3) Push back on the operculum to reveal gills.
4) Cut through the bone at the top and bottom of each gill arch to remove that gill.
5) Observe the gill filaments.
(See pg 64 of revision guide)
Describe the location and structure of the gills in a fish.
- Located under a bony flap called the operculum on each side of the head.
- Each gill is supported by a gill arch and has gill filaments coming off it.
Describe how you can dissect the gaseous exchange system in insects.
1) Use a large insect that has been recently killed.
2) Ensure that dissection tools are sharp, clean and free from rust.
3) Fix the insect to a dissecting board -> Dissecting pins through its legs.
4) Cut and remove a piece of exoskeleton from the along the length of the insect’s abdomen.
5) Use a syringe to fill the abdomen with saline solution. The tracheae appear as a network of very thin, silvery-grey tubes (because they’re filled with air).
6) Observe the tracheae under an optical microscope using a temporary mount slide -> Appear grey again. May be able to see rings of chitin in the walls for support.
What colour do insect tracheae appear when the insect is flooded with saline solution and why?
- Silvery-grey
* Because they’re filled with air
When observing insect tracheae under an optical microscope, what will you see?
- Tracheae appear silvery-grey
* Rings of chitin present in the tracheae walls for support
Describe how lungs in animals and tracheae in insects are supported.
- Lungs -> C-shaped cartilage rings
* Tracheae -> Rings of chitin in the walls
What are some ethical issues with dissecting animals and how can these be removed?
1) Some people argue it is morally wrong to kill animals just for dissections -> So most school dissections are of animals that have already been killed for meat
2) Animals used for dissection may not be raised and killed humanely -> So it’s important that animals are raised and killed in a humane manner
