Adaptations for Gas Exchange

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What happens to the rate of diffusion when the cell increases in size?
Diffusion pathway gets longer so the diffusion from outer cell to centre is slowed
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What needs will not be met if the cell becomes very large?
Supply nutrients (oxygen, glucose)
Remove waste (carbon dioxide, urea)
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Define Gas Exchange
process by which oxygen reaches cells and carbon dioxide is removed from them
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Define ventilation
Process of moving the respiratory medium(air/water)over respiratory surface to maintain conc gradient replacing stale air (high in CO2) with fresh oxygenated air
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Define respiration
Series of chemical reactions that results in release of energy in the form of ATP
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How do you calculate surface area to volume ratio?
Surface area = length x height x number of sides
Volume = length x width x height
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Give an example of a unicellular (single celled) organism
Amoeba - aquatic
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What are features of a unicellular organism
- extremely large SA:V ratio
-Gas exchange across whole surface
-Permeable membrane for diffusion of gases
-No Specialised gas exchange organs
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Give two examples of a simple multicellular organism
Flatworm - aquatic
Earthworm - terrestrial
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What are features of a simple multicellular organism : flatworm
-flattened shape overcomes problem of an increase in size
- increases SA:V so no cell is far from surface(short diffusion path)
-No specialised gas exchange organs
-Exchange gases directly to environment via diffusion
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What are features of a simple multicellular organism : Earthworm
-tubular shape, restricted to damp
-secrete mucus so body is moist for dissolve and diffusion of gases
-elongated for a large SA:V
- exchange gases directly to environment by diffusion across moist surface
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Features continued
-Blood vessels close to body surface so gases can diffuse in and out of blood across cells
-blood circulates in vesells maintaining conc gradient for diffusion
-blood has haemoglobin
- exchange surface = skin
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Why do multicellular organisms require a specialised gas exchange surface?
-more metabolically active
-need method of circulation
-provides large number of gas exchange surfaces to increase the surface area
-toughened body surface so have internal gas exchange surfaces
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What are the three gas exchange surfaces in a :
Fish
Mammal
Insect
gill lamellae
alveoli in lungs
end of tracheoles
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What must all respiratory surfaces be to achieve the max rate of diffusion
thin = short diffusion path
moist = gases can dissolve and diffuse
large SA for diffusion of O2 and CO2
permeable to gases
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What additional feature increases efficiency of gas exchange in organisms that have circulatory system and respiratory pigment?
extensive blood supply

blood circulates to maintain conc gradient

pigment increases 02 capacity of blood
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What do insects require to fly
lots of energy

good oxygen supply to respire
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what do insects not use to transport gases
blood
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where does air diffuse into of an insect and where do these lead
through paired holes of spiracles along each side of body

lead to system of branched chitin lined air tubes = tracheae
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Why is it important that the spiracles can open and close like valves
Open allowing air to diffuse in allowing water to evaporate out

Close so water cant fully evaporate and air cant diffuse in/out
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What ventilates the tracheae in periods of insect activity
movements of the abdomen
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What does the tracheae branch into
Very fine thin walled tracheoles
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Where do oxygen and carbon dioxide diffuse in and out from and to
Oxygen: from end of tracheoles into cells

Carbon Dioxide: out of cells into tracheoles
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What is surface of tracheoles lined with a spiral fold of and what does it do
chitin: allows flexibility and keeps airways open during body movements
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How does the end of tracheoles being fluid filled help the efficiency of gas exchange
oxygen dissolves in fluid and when muscles contract the fluid (with 02) is drawn into the muscle cells
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What are advantages of the tracheal system for gas exchange
o2 supplied directly to tissues
no pigment needed
o2 diffuses faster in air than blood
spiracles close to reduce water loss
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Whats the disadvantage of the insect tracheal system
only efficient in smaller organisms because in larger organisms the number and length of trachea tubes needed is higher increasing the weight restricting movement
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why are gas exchange organs internal for all land living organisms
reduce water loss

reduce heat loss

protection by ribs or exoskeletion in insects
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What problems are caused by the fish living in water
water contains less o2 than air

rate of diffusion slower in water

water is a dense medium so doesn't flow as freely as air
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Give an example of both a cartilaganous fish and a bony fish
Shark

Herring
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What are features of a cartilaginous fish e.g. shark
skeleton entirely of cartilage
almost all live in sea water
5 gill clefts behind head on each side which open at gill slits
water taken in mouth forced through slits when floor of mouth is raised
parallel flow - blood in capillaries circulates in same dir
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What are features of a bony fish e.g. herring
internal skeleton of entirely bone
gills covered with flap called the operculum
counter current flow - blood in capillaires circulates in opposite direction as water flowing over gills
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What is the ventilation mechanism in fish for water flowing in
Mouth - open
Operculum - closes
Floor of buccal cavity - lowers
Volume - increases
Pressure - decreases
Direction of water flow - in through mouth
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What is the ventilation mechanism in fish for water flowing out
mouth - close
operculum - open
floor of buccal cavity - rises
volume - decreases
pressure - increases
direction of water flow - over gills + out of operculum
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What is along each gill arch and then what is on these
many thin filaments

gill lamellae (gill plates)
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What is counter current flow
-blood meets water with higher 02 conc
-gradient for o2 diffusion into blood from water maintained over length of lamellae
-o2 diffuses into blood across lamella length
-more efficent as higher blood oxygen saturation level
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What is parallel flow
-water taken into mouth + blood flows through gill capillaries in same direction as water
-gas exchange efficient at first as steep conc gradient
-halfway along gill lamellae, reached equilibrium so diffusion of 02 and c02 not possible
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How are larvae (tadpoles) adapted for gas exchange
live in water and have gills

adult are terrestrial so live on land
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How are adult amphibians adapted for gas exchage
When inactive diffuse across moist surface = skin
When active the surface is the lungs

Lungs have a simple structure with little infolding of tissues
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Why is there rings of cartilage that support the trachea, bronchi and bronchioles
prevent airways from collapsing during inspiration where pressure is low
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What is the tight compartment of body that enclose the lungs
thorax
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What do goblet cells produce and secret
mucus to trap microorganisms

Cilia then wafts this up and out of trachea
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What happens to the parts of the lungs during inspiration - negative pressure breathing
external intercostal muscle + ribs = muscles contract raisingribs up+out
outer pleural membrane= pulled out reducing pressure in pleural cavity
inner pleural membrane=pulled out
lungs+alveoli=lung surface drawn out, alveoli expands
alveoli pressure=lower
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What happesn to parts of lungs during expiration
External intercostal muscles+ribs= muscles relax moving ribs down+in
Outer pleural membrane= move in
Inner pleural membrane= move in
Lungs+alveoli= lungs move in, alveoli deflate
Alveoli pressure= higher than atmosphere so air moves out
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Why are the alveoli suitable as a gas exchange surface
large SA for gas diffusion
Moist = gases dissolve+diffuse easier
Permeable = 02 and CO2 able to diffuse
Walls of alveoi one cell thick - short diffusion path
Alveolus have extensive capillary network so circulation of blood maintains conc gradient for dif
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What is surfuctant
Chemical substance that covers surface of alveoli and it reduces surface tension preventing alveoli from ticking together and collapsing when breathing out
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What is the function of the intercostal muscle

Function of bronchiole

Function of larynx
upon contraction, ribs pulled up and out increasing thorax volume

Bronchi branch into these smaller tubes

Box shaped structure above trachea that contain coal chords
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Function of alveoli

Function of bronchi

Function of surfactant
Main gas exchange site, large SA

Trachea splits into two of these

Prevents alveoli sticking together and collapsing reducing surface tension also
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Function of trachea

Function of rubs

Function of diaphragm
Tube held open by rings of C shaped cartilage

Bone moved by intercostal muscles, alter thorax size (chest cavity)

Dome shaped muscles relax + contract altering thorax volume
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Function of pleural cavity

Function of epiglottis

Function of pleural membranes
Has pleural fluid that acts as lubricant reducing friction between lungs and inside walls of thorax in ventilation

Flap of skin stopping food entering trachea when swallowing

Acts as lubricant allowing friction free movement against thorax inner wall
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Summary of gas exchange in amoeba
Respiratory medium = water
Gas exchange surface = body surface
Ventilation = no
Blood circulation = no
Respiratory pigmennt = no
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Summary of gas exchange in flatworm
Respiratory medium = water
Gas exchange surface = body surface
Ventilation = no
Blood circulation = no
Respiratory pigmnent = no
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Summary of gas exchange in earthworm
Respiratory medium = air
Gas exchange surface = body surface
Ventilation = no
Blood circulation = closed
Respiratory pigment = haemoglobin
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Summary of gas exchange in fish
Respiratory medium = water
Gas exchange surface = gills
Ventilation = buccal cavity
Blood circulation = closed
Respiratory pigmnent = haemoglobin
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Summary of gas exchange in amphibian
Respiratory medium = air
Gas exchange surface = lungs or moist skin
Ventilation = ribs
Blood circulation = closed
Respiratory pigmnent = haemoglobin
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Summary of gas exchange in insect
Respiratory medium = air
Gas exchange surface = tracheole
Ventilation = abdomen
Blood circulation = open
Respiratory pigmnent = no as oxygen not transported into blood
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Summary of gas exchange in mammal
Respiratory medium = air
Gas exchange surface = lungs - alveoli
Ventilation = ribs or diaghram
Blood circulation = closed
Respiratory pigmnent = haemoglobin
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What are the adapatations of a leaf to carry out gas exchange
Flat, thin leaf blade = short diffusion path
Spongy mesophyll layer = diffusion and maintain gradient
Moist mesophyll walls = allows dissolve and diffuse
Stomatal pores = allow exchange of gases
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What are adaptations of leaves for phtoosynthesis
Large SA - absorb light
Leaves can orientate selves towards sun
Thin leaves - allow light to penetrate lower layers
Cuticle and epidermis transparent - allow light to pass to mesophyll below
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Continues...
Palisade cells enongated and densely packed and may contain chloroplaats
Chloroplast can rotate and move to maximise light absorption
Interecellular air spaces allow co2 to diffuse in and o2 and h20 o diffuse away
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Where are stomata found and how many guard cells surround each pore
on lower epidermis
2
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What is role o stomata
Width of stomatal pores change to control exchange of gases between atomsphere and the leaves internal tissues
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What is unusual,about guard cells
Only epidermal cells that contain chloroplasts

Unevenly thickened cell walls
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What is the mechanism for stomatal , opening
-Potassium ions actively transported from epidermal cells - guard cells
-Starch in guard cells converts to malate by cytoplasms enzymes
-Water potential in guard cells lowered so water enters by osmsos
-Guard cells become turgid and curve because outer wa
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Why are stomata open in day and closed at night
Allow CO2 to diffuse into leaf for photoysynthesis and 02 produced by respiration and water vapour can diffuse out too

Reduce loss of water vapour, co2 levels can trigger the stomatal opening or closing
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Other cards in this set

Card 2

Front

What needs will not be met if the cell becomes very large?

Back

Supply nutrients (oxygen, glucose)
Remove waste (carbon dioxide, urea)

Card 3

Front

Define Gas Exchange

Back

Preview of the front of card 3

Card 4

Front

Define ventilation

Back

Preview of the front of card 4

Card 5

Front

Define respiration

Back

Preview of the front of card 5
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