Unit 2.2 - Adaptations for Gas exchange Flashcards
What are gases always exchanged by?
Diffusion
What do organisms exchange gas with?
The environment
What are some gases that organisms exchange with the environment?
O2 and CO2
When is O2 involved in gas exchange?
For aerobic respiration
Produced by plants
When is CO2 involved in gas exchange?
Waste product of aerobic respiration
Used by plants that photosynthesise
Give an example of a single celled organism
Amoeba
Is gas exchange across the cell surface membrane sufficient for amoeba? Why?
Yes, as it has a large surface area to volume ratio
Which method of gas exchange is the only one required for amoeba?
Gas exchange across the cell surface membrane
What type of organisms cannot rely on diffusion alone?
Larger, multicellular organisms
What can larger, multicellular organisms not rely on alone?
Diffusion
Why can larger, multicellular organs not rely on diffusion alone for gas exchange?
Smaller surface area to volume ratio
What must larger, multicellular organisms have for gas exchange as they cannot rely on diffusion alone?
A ventilation mechanism
(Sometimes) a circulatory system with specialised blood pigments
What do specialised blood pigments do?
Ensure that respiratory gases are exchanged with the body tissue rapidly
Draw and label an amoeba
(See notes)
Where does aerobic respiration occur in an amoeba?
Inside the cell
Describe how respiration occurs in an amoeba
Oxygen concentration is low inside so it moves from an area of high to low concentration down a concentration gradient
Also, it’s non-polar, so it easily passes through the membrane
What is oxygen that allows it to easily pass through a membrane?
Non-polar
Fick’s law
Rate of diffusion = surface area x difference in concentration
————————————————————
Length of diffusion pathway
Diffusion pathway
Distance from cell centre to the middle of the cell wall
What has to increase in Fick’s Law equation for the rate of diffusion to increase?
Surface area or difference in concentration
What had to increase under Fick’s Law for the rate of diffusion to decrease?
Length of diffusion pathway
If an organism is larger in size, what happens to its surface area to volume ratio?
It decreases
What type of organism has a smaller surface area to volume ratio?
Larger organism
Why does an increased size in an organism mean that the surface area to volume ratio decreases and what does this mean for the time taken for gas to diffuse into the organism?
As the organism gets bigger, the surface area increases, but the volume increases more
It’s the surface area that gases diffuse through after all
And…
The length of the diffusion pathway is larger
So, it takes longer for gas to diffuse into the organism
Is it a large or small surface area to volume ratio that provides efficient diffusion?
Large
What diffuses in and out of a flatworm?
O2 in, CO2 out (nothing different lol)
How does the flatworm achieve the best rate of diffusion?
Short diffusion pathway
Increased surface area (long, thin, flat body)
Exchanges gases over its whole body
Why does the earthworm have a more complicated gas exchange system?
It’s a larger organism
Why is relying on diffusion alone not sufficient in the case of the earthworm?
The distance from the cell wall to centre is too great to rely on diffusion alone to provide oxygen to internal organs
Why does oxygen diffuse into organisms anyway?
To provide oxygen for internal organs
What do earthworms have due to the fact that they cannot rely on diffusion alone for gas exchange?
A circulatory system that carries oxygen from the outer surface to the internal body
What does the circulatory system in an earthworm do?
Carries oxygen from the outer surface to the internal body
Sketch and label the circulatory system in an earthworm
(See notes)
What does oxygen do in terms of diffusion n an earthworm and why?
Higher 02 concentration int the air, so 02 diffuses into the blood
Where does oxygen diffuse to and from in an earthworm?
From the air into the blood
Why is there a short diffusion pathway in the circulatory system of an earthworm?
The blood vessels are very close to the body surface
What does the fact that blood vessels are very close to the body surface mean for earthworms?
Short diffusion pathway
What does the blood of earthworms contain?
Haemoglobin
What is haemoglobin in the blood of earthworms?
A protein that binds to oxygen
What’s the name given to haemoglobin in an earthworms blood?
A respiratory pigment
Sketch and label the cell structure in an earthworm
(See notes)
What are earthworms covered in and why?
Mucus, as oxygen first needs to dissolve on the surface of the worm before diffusing into the blood
What allows oxygen to dissolve on the surface of the worm before diffusing into the blood?
Mucus
List the 5 properties of gas exchange surfaces
Large surface area
Thin
Permeable to gases
Moist
Concentration difference
Why is having large surface are beneficial for gas exchange surfaces?
Ensures diffusion is sufficient to provide for the organisms needs
Why is being thin beneficial for gas exchange surfaces?
To provide a short diffusion pathway
Why is being permeable to gases vital for gas exchange surfaces?
To allow respiratory gases to pass through
Why is being moist vital for gas exchange surfaces?
Gases must dissolve before they can diffuse across membranes
Why is having a concentration difference vital for gas exchange surfaces?
To ensure sufficient diffusion of O2 in and CO2 out
Which property of a gas exchange surface ensures that diffusion is sufficient to provide for an organisms needs?
Large surface area
Which property of a gas exchange system is vital to provide a short diffusion pathway?
Being thin
Which property of a gas exchange system is vital in allowing respiratory gases to pass through?
Permeability to gases
Which property of a gas exchange system is important for ensuring that gases dissolve before they diffuse across membranes?
Moist
Which property of gas exchange systems ensure sufficient diffusion of O2 in and CO2 out?
Concentration difference
What’s the gas exchange surface of mammals?
Alveoli
What’s the alveoli to mammals?
The gas exchange surface
Draw and label the lungs
(See notes)
Which process can we use to model lungs and how does this work?
Plastimation
Plastic compound injected into the dead organism and it fills the airways and solidifies
What are bronchioles?
Thin airways that lead to the alveoli
Thin airways that lead to the alveoli
Bronchioles
What kind of tissue do the bronchioles have and why is this useful?
Ciliated epithilum
Cilia move mucus from the lungs towards the mouth - carries any small particles out from the lung in the mucus to avoid disease
What do the network of capillaries on an alveoli contain and why?
Blood with low levels of oxygen for oxygen to diffuse from the alveoli to the blood
What type of tissue do the alveoli’s cells have and why is this useful?
Squamous epithilum
Broad, flat and thin in cross-section
= short diffusion pathway between alveoli and capillaries in the blood
Where are the red blood cells situated in the capillaries? Why is this useful?
Right along the edges = short diffusion pathway between alveoli and red blood cells
What are the properties of the alveoli which enable them to function as gas exchange surfaces in mammals?
Thin
Large surface area
Moist
Concentration difference
Permeable to gases
Why are alveoli thin and what does this lead to?
Shape of squamous epithilum (+ capillary walls are 1 cell thick) = short diffusion pathway
Why do alveoli have a large surface area and what does this lead to?
Millions of alveoli + large capillary network surrounding each alveolus = sufficient diffusion
Why are alveoli moist and what does this lead to?
Lungs are internal = prevents water loss + tissue fluid lining allows gases to dissolve and diffuse across
Why do alveoli have a concentration difference and what does this lead to?
Capillary network = low oxygen blood reaches the alveoli so that there’s a concentration gradient for it to diffuse form the alveoli to the blood + ventilation ensures the O2 concentration of the alveolus is high
Why are alveoli permeable to gases?
To allow respiratory gases to pass through
Where does oxygen diffuse to and from in terms of the alveoli and blood?
From the alveoli to the blood
What are the advantages of internal gas exchange systems?
Reduces heat loss to enviornment
Reduces water loss to environment
Protected from physical damage
Protection from infections
Give an example of an internal gas exchange system?
The lungs
What is a surfactant?
An anti-sticking chemical
Where is a surfactant to be found?
Covering the surface of each alveolus
Whats the name for the anti-sticking chemical covering the surface of each alveolus?
Surfactant
Is surfactant a mucus? Why?
No, mucus is much thicker
What’s the purpose of surfactant and how does it do this?
Prevents the alveoli collapsing when breathing out - reduces surface tension
Also, it allows gases to dissolve before they move in or out
What do surfactants contain?
Phospholipids and proteins
What are babies lungs filled with and what’s the solution to this when they’re born?
Liquid (they got their oxygen through the umbilical cord)
Surfactant slows the lungs to open out, allowing the lungs to fill with air
What’s often given to premature babies and why?
Due to them being born before the production of the surfactant, they’re often given it, as without it, the alveoli in their immature lungs would stick together
How is the trachea a kept from collapsing?
C-shaped cartilage
What does the “c-shape cartilage” do?
Stops the trachea from collapsing
Why IS the c-shape cartilage that stops the trachea from collapsing c-shaped?
It’s not a complete ring and doesn’t meet at the back as this allows the oesophagus behind it to bulge as a bonus of food is swallowed, without meeting a hard structure, which would prevent food from moving past
Ventilation
Breathing
Brings gases to or from a gas exchange surface
Does ventilation occur in all organisms?
Only some
What does the ventilation of the lungs occur via?
Negative pressure ventilation
What do we have 2 sets of in the lungs and what are they?
2 sets of intercostal muscles
Internal and external
What do the internal and external intercostal muscles in the lungs form together?
Antagonistic pairs
Name antagonistic pairs in the lungs and explain what this means
Internal and external intercostal muscles in the lungs
Work against each other - relax when the other contracts
Thoracic cavity
Place where the lungs sit
Place where the lungs sit
Thoracic cavity
Draw and label the structures of a lung required to explain inspiration and expiration
(See notes)
What type of process is breathing in and why?
Active process (muscle contraction requires energy)
Fancy WJEC words for inhalation and exhalation
Inspiration
Expiration
Describe the steps of inspiraiton
- The external intercostal muscles contract
- The ribs are pulled upwards and outwards
- At the same time, the diaphragm muscles contract, so the diaphragm flattens
- The outer pleural membrane is attached to the thoracic cavity wall so it is pulled up and out with the ribs, and the lower part is pulled down with the diaphragm
- Inner membrane follows = increase in the volume of the thoracic covalent as the lungs expand
- Increases the volume of the alveoli
- Reduces air pressure in the lungs
- Atmospheric air pressure is now greater than the pressure in the lungs, so air is forces into the lungs as it moves from the atmosphere to the lungs down a pressure gradient
Why is it called “negative pressure ventilation”?
As during inspiration, the air pressure in the lungs becomes lower than the atmospheric air pressure
Pulmonary
Relating to the lungs
Word for relating to the lungs
Pulmonary
What type of process is breathing out?
Mainly passive
Describe the steps of expiration
- The external intercostal muscles relax
- The rubs move downwards and inwards
- At the same time, the diaphragm muscles relax, causing the diaphragm to dome upwards
- The pleural membranes move down and in with the ribs, and the lower parts move up with the diaphragm
- The elastic properties of the lungs allow their volume to decrease, decreasing the volume of the volume inside the alveoli + lung volume decreases
- Increases the pressure in the lungs
- Air pressure of the lungs is now greater than atmospheric pressure, so air is forces out of the lungs, down a pressure gradient
What property of the lungs allows their volume to decrease?
The elastic properties of the lungs
What’s attached to the thoracic cavity wal?
The outer plural membrane
Which muscles contract upon inspiraiton?
The external intercostal muscles contract
What happens to the diaphragm upon inspiration?
The muscles contract and it flattens
In which direction are the ribs pulled during inspiration?
Upwards and outwards
Which intercostal muscles relax during experiation?
External intercostal
What do the external intercostal muscles do during expiration?
Relax
What do the ribs do during expiration?
Move downwards and inwards
What does the diaphragm do during expiration?
Diaphragm muscles relax and it domes upwards
What’s the importance of ventilation in the lungs?
it’s needed to maintain a concentration gradient between the air in the alveoli and the blood
What can cilia NOT sweep out of the lungs and why?
Bacteria - they’re far too small
What are the lungs surrounded by?
2 membranes - pleural membranes
Pleural membranes
Membranes that surround the lungs
What are the 2 types of pleural membrane?
Outer an inner
What’s the outer pleural membrane attached to?
The chest wall
What’s the inner pleural membrane attached to?
Covers the lungs
What’s between the pleural membranes?
Pleural filled space (pleural cavity)
What does pleural cavity do?
Creates a surface tension so that the outer and inner pleural membranes reman in contact
What do the outer and inner pleural membranes do with each other?
Slide over each other to enable the movements of the rib cage and diaphragm
What could cause the lungs to collapse?
If a bacterial infection or infection occurs to the pleural membrane
Why would a bacterial infection cause the lungs to collapse?
Bacteria would create a gas in the pleural cavity
What type of injury could cause the lungs to collapse?
Puncture of the membrane could displace the liquid of the pleural membrane
If a bacterial infection or injury occurs to the pleural membrane, what can happen?
The lungs can collapse
What cannot occur if the lungs have collapsed?
Negative pressure won’t be able to be created in order to respire
Give examples of some types of amphibians
Frogs, toads, newts, salamanders
What usually happens to amphibians eggs once they hatch? Give an example
They hatch into their aquatic form (e.g - tadpoles) and then go through metamorphosis to reach different stages (e.g - frog)
What type of animals go through metamorphosis from their aquatic form when hatched?
Amphibians
What’s different about the axolotl compared to other amphibians?
It doesn’t go through metamorphosis from its large form - it just keeps getting bigger in this larva form and remains in the water
What’s the gas exchange surface of the axolotl and what occurs here?
Their gills - they get oxygen dissolved from the water and give out CO2
Which amphibian is different to the others in that it remains in its aquatic form permanently?
Axolotl
How do most adult amphibians exchange gases?
Most have lungs, that are simple and primitive
However, they can also exchange gases directly through their thin, permeable skin
Does a tadpole have lungs?
No, it has gills for gas exchange
How come amphibians can exchange gases through their skin?
It’s thin and permeable
Describe the lungs of an amphibian
Simple and primitive
What can amphibians do in water?
Can exchange gas through the outer body surface for a long time
When do amphibians use their lungs? Give some examples
During periods of increased activity
Swimming, jumping or mating
What is used by amphibians during periods of increased activity?
Lungs
What’s the name for the respiration that uses lungs?
Pulmonary respiration
What’s the name for the respiration that uses the skin to respire?
Cutaneous respiration
Why do most amphibians live in moist places?
They use their skin to respire - needs to be kept moist for gas exchange
Are amphibians cold or warm blooded?
Cold blooded
What does the fact that amphibians are cold blooded mean for them?
They don’t use much energy to keep warm and don’t require as much O2 as mammals
Are mammals warm or cold blooded?
Warm
What does the fact that mammals are warm blooded mean for them?
They use metabolic processes (e.g - respiration) to keep warm, using O2 and generating internal heat)
Cutaneous respiration
Using the skin to respire
Pulmonary respiration
Using the lungs to respire
Name the characteristics of the respiratory surface for amphibians, reptiles and birds
Large surface area
Moist surface
Internal lungs
Ventilation mechanism
Thin walls
Circulatory system with blood pigments
What does the fact that amphibians, reptiles and birds have a large surface area mean for them?
Rapid diffusion of respiratory gases
How do amphibians regulate their body temperature (as they’re cold blooded and so don’t use metabolic processes)?
Use the environment (e.g - go in the sun, go in the shade)
What does the fact that amphibians, reptiles and birds have a moist surface mean for them?
Facilitates rapid diffusion of gases
What do the fact that reptiles and birds have internal lungs mean for them?
Minimised loss of water and heat
Which of the following don’t it necessarily apply to all that they have lungs?
amphibians, reptiles and birds
Amphibians
What does the fact that amphibians, reptiles and birds have respiratory surfaces with thin walls mean for them?
Short diffusion pathway
Why do amphibians, reptiles and birds have circulatory systems with blood pigments?
To carry oxygen (e.g - haemoglobin)
Why is a ventilation mechanism important in amphibians, reptiles and birds?
Forces the respiratory medium (air) to and from the respiratory surface
O2 is brought to and CO2 is removed from the gas exchange surface
What does an inactive amphibian use for gas exchange?
Its moist skin
What does an active amphibian use for gas exchange?
Simple lungs
What are the lungs of an amphibian pretty much?
A simple pair of hollow sacs
Describe the surface area of an amphibians lungs
Highly folded to give them an increased surface area, but still relatively small compared with human lungs
What does an amphibian in the tadpole sage use for gas exchange?
Gills
Describe the skin of a reptile
Impermeable to gases, and so cannot be used as a respiratory surface
Compare the lungs of reptiles to those of amphibians
More efficient, and so gas exchange occurs exclusively here
Where does gas exchange occur exclusively in reptiles?
In the lungs
How are the lungs of reptiles more efficient than those of amphibians?
More complex folding
Ventilation is aided by the movement of the ribs by the intercostal muscles
What is ventilation aided by in the lungs of a reptile?
The movement of the ribs by the intercostal muscles
What can the lungs of a reptile be described to be?
Sac like
Do reptiles’ lungs have diaphragms?
No
Do reptiles’ lungs have ribs?
Yes
Are birds warm or cold blooded?
Warm blooded
Why is efficient gas exchange essential in birds?
They have a high respiration rate
Describe the lungs of a bird
Small and compact
What are bird lungs composed of?
Numerous branching air tubes called bronchi
Bronchi
Branching air tubes of birds
Parabronchi
Smaller air tubes of the bronchi in the birds lungs, with an extensive blood capillary network
Smaller air tubes of the bronchi in a birds lungs
Parabronchi
What do Parabronchi in birds lungs have?
An extensive blood capillary network
Where does gaseous exchange take place in a birds lungs?
The blood capillary network of the Parabronchi
What do Parabronchi end in?
Thin walled air sacs which help in ventilation (act like bellows to push air out of them)
What is the ventilation of the bird lung bought about by?
The movement of the ribs
Why is gas exchange effective in bird lungs?
Air passes the gas exchange surface twice (during inhalation and expiration)
Why is it advantageous that air passes the gas exchange surface twice in the lungs of a bird (during inspiration and expiration)?
Provided effective gas exchange
What does air pass twice during inspiraiton and expiration in bird lungs?
The gas exchange surface
What happens to birds during flight in terms of ventilation?
The action of the wing muscles ventilate the lungs
Draw and label the process of gas exchange in insects
(See notes)
What do the trachea in insects have?
Rings of chitin
Which part of the gas exchange system in insects has chitin and which part doesn’t?
Chitin - trachea
No chitin - trachioles
What do the trachioles do in the gas exchange system in insects?
Branch onto tissues and muscles
Do insects have lungs?
No
What else do infects not have in terms of gas exchange apart from lungs?
A circulatory system to transport O2 around the body
What’s the only type of circulatory system that insects have?
Ones for nutrients
What do insects have for gas exchange instead of lungs?
A system of branching tubes throughout the body
What feature do insects have that would TECHNICALLY make their bodies effective for gas exchange?
Large surface area to volume ratio
Draw and label an insect (in terms of gas exchange)
(See notes)
Why can’t insects use their bodies for gas exchange?
The chain exoskeleton is impermeable to water and gases
How many spiracles are on each segment on an insect?
2
How do insects get air into their spiracles?
Pump their abdomens in and out to get air into the spiracles
What do the spiracles of an insect come in?
Pairs
Where d an insect’s spiracles lead to?
Trachea
What happens to the trachea of insects?
Divides into branching trachioles
Do trachioles have a lining of chitin? (insects)
No, only the trachea
Where do the trachioles of insects end?
In close contact with muscle cells
Where does gas exchange actually occur in insects?
In the gap between the trachioles and muscle cells
What limits the size of an insect and why?
Its gas exchange system, as if it grew much bigger, there would be too much tubing and the system would be too heavy to fly
How does the gas exchange system of insects actually work?
Ends if trachioles are filled with fluid
The end enters the tissue
The ends of the trachioles are also devoid of cuticle - the respiratory surface is very thin, so O2 diffusion into cells is easy
As respiration occurs in the cell, the products of respiration accumulate in the cell and force the fluid in the trachioles to enter the tissue
The exit of fluid creates low pressure in the tubes and draws in more O2 to the tissues where it’s reacted
What happens to an insect when it’s active in terms of gas exchange?
Surface area for gas exchange increases
Give some examples of bony fish
Cod, salmon, trout
What type of animals are bony fish and what does this mean for them?
Aquatic
Exchange gases with the enviornment
Gas exchange surface in fish - what’s good about these?
Gills - highly adapted for gas exchange in water
What are fish gills covered by?
The operculum
(Flap of tissue)
Why is it important to have an effective gas exchange system in water?
Denser medium than air - much harder to move water in and out of narrow tubes
Low O2 levels compared to air
What’s the other type of fish (not bony)?
Cartilaginous
Examples of cartilaginous fish
Sharks
Catfish
What works differently between bony and cartilaginous fish?
Their gills
Draw and label a fish gill
(See notes)
What’s the gas exchange surface of the gill?
Gill filaments
Gill rakers purpose
Capture food so that they don’t clog up the gills
Gall arch purpose
Supports the gill
What are gill filaments?
A specialised respiratory area
How are gills adapted for gas exchange?
Large surface area - 100s of gill filaments on each gill
Gill filaments are thin
What must be done to water in a bony fish and why?
Is a denser medium with relatively low O2 content]
Must be forced over the gill filmaments
What prevents a fish gill from collapsing?
Density of water
Why is it important that a fish gill doesn’t collapse?
To maintain a large surface area
How is water forced over a fish’s gills?
By a ventilating mechanism
Describe the flow of water over a fish gill
One way - unidirectional
Draw and label the inside of a fish’s head to help explain negative pressure ventilation
(See notes)
What’s the name of the type of ventilation that occurs in bony fish?
Negative pressure ventilation (like humans)
What does an opercular flap do?
Can open and close to allow water to flow our behind the head of the fish
Describe the steps of negative pressure ventilation taken when a fish opens its mouth
Operculum closed
Lowers the floor of the buccal cavity
This increases the volume inside the cavity
This decreases the pressure inside the cavity
Water flows in from high to low pressure
Describe the step of negative pressure ventilation taken when a fish closes its mouth
Operculum opens
The floor of the buccal cavity is raised
This decreases the volume inside the cavity
This increases the pressure inside the cavity
Water is forced over the gills into the opercular cavity
Water pressure forces the operculum to open
Water exits through the operculum
Draw and label a diagram to show counter-current flow in a bony fish
(See notes)
Which part of the gill is well adapted for gas exchange?
Gill lamellae
Adaptations of gill lamellae for gas exchange
Thin to create a short diffusion pathway
Increase the surface area of the gill filament even more
Excellent blood supply (why fish gills always look pink)
Always moist
Which is most effective for gas exchange…
Counter-current flow or parallel flow?
Counter-current flow
What occurs during counter-current flow?
Water and blood flow in opposite directions across the gill plate
Water always has a higher oxygen concentration than the blood, sp oxygen diffuses into the blood down a concentration gradient, across the entire gill plate?
Where is oxygen diffused into the blood from the water during counter-current flow?
Across the entire gill plate
Compare the flow of water between counter-current and parallel flow
Water flows across the filament (though the gill plates) in both
C.C - opposite direction to blood flow in the gill capillaries
P - same direction as blood flow in the gill capillaries
Compare the concentration gradients between counter-current and parallel flow
C.C - a steep oxygen concentration gradient is maintained, allowing diffusion of oxygen across the entire gill plate
P- oxygen concentration gradient is not maintained - equilibrium is reached between the water and the blood, so diffusion ends halfway across the gill filament
Compare the diffusion of oxygen from the water to the blood between counter-current and parallel flow
C.C - across the entire gill plate
P - doesn’t occur across the entire gill plate
Compare the rate of diffusion between counter-current and parallel flow
C.C - high
P - lower and decreases as equilibrium is reached
Compare the amount of oxygen absorbed into the blood between counter-current and parallel flow
C.C - a greater amount
P. - less oxygen (not slower)
Is oxygen adsorbed into the blood slower during parallel flow?
No, just less of it
Compare the % oxygen saturation of the blood between counter-current and parallel flow
C.C - higher
P - lower
Which flow system is less efficient?
Parallel
Draw and label a diagram to represent counter-current flow
(See notes)
Why is there constant diffusion with counter-current flow?
Always a concentration difference between water and blood
Sketch a graph to represent counter-current flow
(See notes)
Sketch a graph to represent parallel flow
(See notes)
What are the 2 mechanisms by which bony fish maintain a concentration gradient of their gas exchange surface?
Counter-current flow
Negative pressure ventilation
What would bony fish do in terms of ventilation in higher temperatures and why?
Open and close their mouths faster
Warm water has less O2 dissolved in it
With more ventilation movements, the more water is pumped over the gills to provide the same amount of oxygen
Why would gill filaments/lamellae not provide an efficient gas exchange system on land?
Would dry out - no longer moist for O2 to dissolve
Would collapse and stick together, reducing the surface area for gas exchange
Why do plants need to exchange gases?
For respiration and photosynthesis
What’s the main gas exchange surface of a plant?
The leaf
What is an ideal organ for exchanging gases in a plant?
The leaf
What is a leaf’s structure related to?
Its function
Lamina
Leaf blade
Leaf blade
Lamina
How is a leaf’s structure related to its function as a gas exchange surface?
Leaf blade (Lamina) - thin and flat with a large surface area
Diffusion pathway for gases - short
Flowering plant
Angiosperm
Angiosperm
Flowering plant
What type of plant do we need to be able to label its leaves?
Angiosperm (flowering plant)
Draw and label a photo micrograph of a leaf’s transverse section
(See notes)
What does the lower epidermis include?
Guard cells
What does the vascular bundle consist of?
Xylem
Cambium
Phloem
What do the xylem, phloem and cambium make up?
The vascular bundle
What are leaves responsible for?
Exchanging gases
Trapping light for photosynthesis
Midrib
Strengthened vain in the middle of a leaf
Strengthened vain in the middle of a leaf
Midrib
What does the midrib do?
Carries the vascular bundle (Xylem and phloem tubes)
Carries the products of photosynthesis
Makes the leaf rigid
Name the adaptations of leaves for photosynthesis
Large surface area
Thin
Air spaces in the spongey mesophyll
Cuticle and epidermis are transparent
Palisade mesophyll cells are elongated and densely arranged in layers
Palisade cells are packed with chloroplasts and arranged with their long axes perpendicular to the surface
Chloroplasts rotate and move within mesophyll cells
Significance of a large surface area for gas exchange in leaves
Room for many stomata
Significance of a leaf being thin for gas exchange
Diffusion pathway for gases entering and leaving is short
Significance of air spaces in the spongey mesophyll for gas exchange in leaves
Reduce diffusion distance for CO2
Allows gas to circulate
Allows oxygen and CO2 to diffuse between the stomata and the cells
Adaptations of leaves for gas exchange
Large surface area
Thin
Air spaces in the spongey mesophyll
Significance of a large surface area of leaves for photosynthesis
Capture as much light as possible
Significance of leaves being thin for photosynthesis
Light penetrates through leaf
Significance of air spaces in the spongey mesophyll of leaves for photosynthesis
Allow CO2 to diffuse to the photosynthesising cells
Significance of the cuticle and epidermis being transparent in a leaf for photosynthesis
Light penetrates to the mesophyll
Significance of palisade mesophyll cells being elongated and densely arranged in layers in leaves for photosynthesis
Can accommodate a large number of cells
No cross walls to prevent light from penetrated through the cell = capture as much light as possible
What’s the main photosynthetic tissue of a leaf?
Palisade mesophyll
What’s the significance of palisade cells being packed with chloroplasts and ranged with their long axes perpendicular to the surface in leaves for photosynthesis?
Capture as much light as possible
Significance of chloroplasts rotating and moving within mesophyll cells in leaves
Moves into the best position for maximum absorption of light
(For example, we see plants on windowsills angled towards the window after a few days in order to capture sunlight)
What’s the waxy cuticle secreted by?
Epidermal cells
What’s the purpose of a leaf’s waxy cuticle?
Stops water from evaporating from the leaf surface - reduces water loss
What are the adaptations of the spongey mesophyll for gas exchange and why are they important?
Large surface area - gaseous exchange
Air spaces - reduce diffusion distance for CO2, allow O2 and CO2 to diffuse between the stomata and the cells
Moist - absorb CO2 and dissolve gases
Stomata pores on the base of the leaf - allow gases to enter the air spaces (O2 out, CO2 in) + water leaves through the stomata
Where are the stomata pores on a leaf?
On its base
What do stomata pores do?
Allow gases to enter the air spaces
Allow water to leave
Do plants require oxygen?
Yes
Where do plants obtain the gases they need through?
Through their leaves
Which gases to plants require and for what?
O2 - respiration
CO2 - photosynthesis
What do plants do in terms of photosynthesis and respiration?
Do both simultaneously (O2 produced and taken in)
What gas exchange generally occurs in a plant in the daytime?
O2 out, CO2 in
What happens to plants in terms of gas exchange when it’s light?
Use up a lot of CO2
O2 is produced as waste when photosynthesising
Cells are still respiring, but not using much O2
What’s produced as waste when plants photosynthesise?
O2
What is a lot of used when photosynthesising?
CO2
What gas exchange occurs when it’s dark?
O2 in, CO2 out
What do plants do in terms of gas exchange when it’s dark?
No light to photosynthesise, so plant cells are only respiring
Why are plant cells only respiring when it’s dark?
No light to photosynthesise
What’s the average gas exchange that occurs in plants?
Plants produce more O2 than they use up
Stomata definition
Pores on lower leaf surface and their aerial parts of a plant bounded by two guard cells, through which gases and water vapour diffuse
What are stomata bounded by?
Guard cells
What do guard cells do?
Bind stomata
What diffuses through stomata?
Gases
Water vapour
Draw and label an open stoma
(See notes)
Draw and label a closed stoma
(See notes)
What are guard cells?
Specialised cells either side of the stomata
Word for 1 v.s plural stomata
Stoma = 1
Stomata = 2+
What do guard cells have that other epidermal cells don’t and why is this?
Chloroplasts
Very metabolically active and produce carbohydrates and store it as starch
Describe the walls of guard cells
Thick inner wall
Thin outer wall
What happens to a guard cell when it swells and why?
Becomes a curved sausage when it swells to open the stomata pore due to it having a thick inner wall
When do guard cells become like curved sausages (lol) and why? What does this lead to?
When they swell due to the thick inner wall
Stomatal pore opens
What can guard cells do?
Change shape to open and close the stomata
How do guard cells open and close the stomat
Change shape
What does guard cells opening and closing the stomata do?
Helps control gas exchange and water loss
When would the stomata open?
During the day - needs to actively photosynthesise and take CO2 in
Describe the steps of stomatal opening
During the day, if light intensity is sufficient, potassium ions (K+) are pumped, by active transport, into the guard cells
As a result, stored starch is converted into malate (which is soluble…)
This lowers the water potential (becomes more negative)
Water enters by osmosis down a water potential gradient
The guard cells swell and become turgid and curve apart because their outer walls are much thinner than their inner walls
This opens the stomatal pore, allowing gas exchange
Is starch soluble or insoluble? what does this mean?
Insoluble - lots an be stored
Is malate soluble or insoluble and what does this mean?
Soluble
The water potential of the cell goes down when its released
When does stomatal closure occur?
At night, with low light intensities an we also want to avoid water loss
Describe the process of stomatal closure
When light intensity is too low for photosynthesis, potassium ions diffuse don a concentration gradient out of the guard cells
Malate is converted back into starch by condensation reaction
The water potential of the guard cell increases (becomes less negative)
Water leaves the guard cells by osmosis
The guard cell becomes flaccid - this closes the stomatal pore
This prevents gas exchange but also reduces water loss
What does the closure of the stomatal pore lead to?
The prevention of gas exchange
Reduces water loss
What do guard cells do in terms of water loss?
Reduce (not avoid)
At which point is the cartilage adapted so that the trachea doesn’t collapse?
When breathing in
What do cilia move from the lungs?
Mucus
Why is having internal lungs an essential adaptation to a terrestrial mode of life?
Prevents water and heat loss
How is a concentration gradient maintained between the alveolar air and blood?
Ventilation
Brings fresh oxygen to the alveoli and removes CO2
Circulation
Removed oxygen from the alveoli and brings CO2
What does a surfactant ACTUALLY do?
Decreases surface tension between fluid molecules
Reduces cohesive forces
Stabilises alveolar wall
Prevents alveolar wall from collapsing and sticking together
What does water loss in plants occur via?
Transpiration
Transpiration
The evaporation of water vapour from the leaves of the plant through stomata into the atmosphere
Why do multicellular organisms have both a good blood supply and a ventilation mechanism?
To maintain a concentration gradient
How do the lungs of both reptiles and birds work generally?
Sac-like and act like bellows
What do insects exchange gases with directly and why?
Tissues
Have no blood or pigments like haemoglobin
What help reduce water loss in insects?
Chitin and spiracles
How do spiracles prevent water loss?
Can close
Name 3 adaptations for gas exchange exclusive for insects?
-tracheal system provides a large surface area
-tracheole walls are thin
-tracheole ends filled with fluid (dissolve gases)
How are insects adapted for dry environments?
Spiracles can close
Tubes lines with chitin
Both prevent water loss
Which part of the lungs become restricted and inflamed during an asthma attack?
Bronchioles
What’s it important to note about the concept of water and heat loss due to internal gas exchange surfaces?
It’s only REDUCED, not prevented
Why do the muscle fibres of the tracheoles of an insect have a small diameter?
To ensure a short diffusion pathway to supply sufficient oxygen
Features of fish gills for efficient gas exchange
Large surface area (for diffusion)
Thin (short diffusion pathway)
Permeable
Good blood supply
(NOT moist)
How have fish overcome the problem of water being a dense medium with relatively low oxygen content?
Forced over the gill by ventilation mechanisms
Unidirectionally
Counter-current flow = concentration gradient is maintained across the entire gill plate
Draw a graph for counter-current flow, including arrows for the direction of flow of water and blood
(See notes)
How is a concentration gradient maintained in mammas gas exchange surfaces?
Ventilation
Takes oxygen away from the gas exchange surface
Standard deviation
How dispersed data is in relation to the mean
What does a high value for standard deviation represent?
That data are more spread out from the mean
What does a low value for standard deviation represent?
That data are more clustered around the mean
Adaptations of bony fish for efficient respiration
Gills have a large surface area due to there being 100s of gill filaments on each gill
Gills are thin = reduced diffusion distance
Gills are permeable
Gills receive a good blood supply
Ventilating mechanism
How come the gills of a fish have a large surface area?
There’s 100s of gill filaments on each gill
How do the abdomen movements of an insect link to its ventilation?
Abdomen movements cause changes in pressure
= air movement through tracheal system
What does water loss from the stomata cause and what does this lead to?
Tension
Water pulled up via xylem
What have the lowest metabolic rate - amphibians or mammals?
Amphibians
How are stomata different to epidermal cells?
Chloroplasts
Unevenly thickened cell walls (thin outer wall, thick inner wall)
What does stomata closure do to water loss?
Reduces it (doesn’t stop it)
How come gill filaments of fish are thin?
1 cell thick epithelium
What does having more cells tend to mean in an organism?
Higher metabolic demand
What type of organisms have higher metabolic demands?
Multicellular
What does being cylindrical do to a surface area to volume ratio?
Increases it
What do Collenchyma have in their walls?
Uneven thickening of cellulose
What do Collenchyma do?
Give support to short- lived structures
Does Collenchyma contain lignin?
No
How can we identify Collenchyma?
Star shaped structures between cells
What often occurs to Collenchyma when preparing it and why?
Thinner areas of the cell walls often breaks as the cells are dehydrated when preparing
