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Adaptations for Gas Exchange
Terms in this set (47)
What is gas exchange?
The transportation of oxygen to cells and carbon dioxide away from cells.
What is ventilation?
Ventilation is the movement of a respiratory medium over the respiratory surface.
What type of flow do cartilaginous fish have and what effect does this have on the rate of gas exchange?
Its extremely efficient at first because theres a steep concentration gradient between the blood and water. However, equilibrium is eventually reached and gas exchange stops.
Describe the ventilation mechanism in fish.
-Buccal floor lowers: volume increases, pressure decreases so water moves in down a pressure gradient
-Buccal floor raises and operculum opens; volume decreases, pressure increases so water moves out the operculum, passing over the gills.
What are the features of bony fish?
4 gill arches covered by an operculum, bony skeleton,
What are the features of cartilaginous fish?
5 gill clefts, cartilage skeleton, live in sea water
Why can unicellular organisms survive with simple diffusion as their gas exchange method?
They have a large SA:Vol ratio and an extremely short diffusion path. They arent as metabolically active as multicellular organisms so dont require as much oxygen
Why do multicellular organisms need a specialised gas exchanged system?
-Greater demand of 02 since more metabolically active
-Smaller SA:Vol ratio as size increases
-Large diffusion distance to cells so simple diffusion is inefficient as its too slow
-Tough exterior so gas exchange surfaces are normally internal
-Need a method of circulation to distribute gases around the body
Give an example of a unicellular organism and how its adapted for gas exchange.
Aquatic: moist to allow gases to dissolve
Extremely large SA:Vol ratio
Diffusion occurs over whole surface
Name and explain the features a specialised gas exchange surface needs to have.
Moist to allow gases to dissolve
Good blood supply to maintain conc. gradient
Thin for short diffusing pathway
Large SA for increasing rate of diffusion
Permeable to allow exchange.
Describe the structure of the gills of bony fish
The gills are made up of a gill arch, on which there are several gill filaments. On these filaments, there are gill plates, which have a blood supply and therefore the filaments have a large surface area.
How are the gills adapted as specialised gas exchange systems?
The gills are kept moist by water.
The gill plates are thin to provide for a short diffusion path for gas exchange.
The gill plates have their own blood supply for gas exchange.
There are many filaments on the gill arch to increase the surface area to volume ratio.
Is parallel flow or countercurrent flow more efficient and why?
Countercurrent flow is more efficient because the oxygen concentration gradient is maintained over the whole gill plate and it results in a higher saturation of oxygen in the blood.
Why do insects need specialised gas exchange surfaces?
Insects fly and this requires large amounts of energy therefore the oxygen demand is greater and simple diffusion is inefficient.
What type of flow do bony fish have and what effect does this have on the rate of gas exchange?
The blood flows in an opposite direction to the water so a concentration gradient is maintained over the whole gill plate. Equilibrium is never reached so the blood has a higher saturation of oxygen at the end.
What is the specialised gas exchange surface in insects?
Describe the ventilation process in insects.
The spiracles in insects open, causing air to move in down the trachea and directly to the tracheoles (chitin lined air tubes) without a respiratory pigment.
How is ventilation more efficient in insects?
Theres no respiratory pigment.
The respiratory medium goes directly to the gas exchange.
02 is transported as a gas, not dissolved, so it travels faster.
What is the role of chitin in the tracheoles?
It is strong so it prevents the tracheoles from collapsing.
What aids ventilation when insects are active?
Movements of the abdomen.
Why would the spiracles in insects close?
To prevent dehydration during dry weather and keep it moist.
What additional features might specialised gas exchange surfaces have and why are they useful?
RESPIRATORY PIGMENT; higher saturation/amount of 02 carried
EXCESSIVE BLOOD SUPPLY; maintain concentration gradient on the exchange surface
Why are the gas exchange surfaces internal in terrestrial animals?
-to avoid water loss
-the tough exteriors protect the internal gas exchange surfaces
-reduce heat loss
Explain how a flatworm is adapted for its type of gas exchange and what type of exchange that is.
▪the exchange is thorugh the moist surface of the skin as an aquatic being
▪being flat increases the surface area:volume ratio
▪no cell is far from the surface so simple diffusion is sufficient
Explain how an earthworm is adapted for its type of gas exchange and what type of exchange that is.
▪secretes mucus to keep surface moist
▪elongated shape for increased SA:V ratio
▪blood vessels ckose to the surface for diffusion
▪blood circulates in vessels to maintain a conc gradient for CO2 to leave and O2 to diffuse in
What is the method of gas exchange in amphibians when theyre active and when theyre inactive?
Active: moist skin and lungs
Inactive: moist skin
What are the adaptations of an amphibians lungs that aid gas exchange?
Infolding of gas exchange tissue
What are the needs of the cell that gas exchange is crucial for?
Removal of waste
How is the rate of diffusion faster in insects?
No transport medium; respiratory medium travels straight to gas exchange surface
No respiratory medium or pigment.
Reduced water loss
How do larger organisms increase surface area?
Infolding of structure.
Describe the reasons for differences between gas exchange in fish and in terrestrial animals.
Water has a lower conc of O2
Water is more dense than air so doesnt flow as freely
Rate of diffusion is slower in water than air.
What is the reason for ventilation in fish?
It increases the efficiency of gas exchange as fresh water moves over the gills.
Describe the process of inspiration in humans.
The intercostal muscles contract, causing the ribs to move up and out. The diaphragm contracts causing it to flatten. This increases the volume of the thorax thus decreases the pressure, causing air to move in down a pressure gradient.
How are the alveoli adapted for gas exchange?
The alveoli are only one cell thick so they have a short diffusion pathway
They're moist for gases to dissolve and also have a capillary network in close proximity for gas exchange.
They have a large surface area
What is the surfactant's role and why is it important?
The surfactant is a phospholipid that prevents the moist alveoli walls from being pulled in by the cohesion of water molecules, by reducing surface tension.
What is the role of cartilage in the human breathing system?
Surround the trachea and bronchi to prevent it from collapsing during inspiration.
What are the bronchi?
The trachea branch into these which eventually branch into bronchioles which lead to alveoli.
What is the larynx?
It contains the vocal chords and is above the trachea
What is the role of the epliglottis?
A flap of skin covering the windpipe to prevent food from entering it when swallowing.
What is the pleural membrane?
It acts as a lubricant prevent friction against the inner wall of the thorax and lungs.
Explain how a leaf is adapted for gas exchange
Thin and flat leaf: short diffusion pathway & greater SA:vol ratio
Spongy mesophyll are moist for gas dissolving
Stomatal pores allow exchange of gases
Permeated by air spaces
Mesophyll have thin permeable walls
What are the adaptations of the plant for photosynthesis?
The waxy cuticle and palisade mesophull layers are transparent to allow light in.
Waxy cuticle prevents water loss.
Palisade mesophyll are densely packed and contain chloroplasts, which absorb light and can rotate to absorb more light
The leaf is thin to allow light through
Large S.A to absorb maximum light
Explain the process of stomatal opening
K+ ions transported into the guard cells from epidermal cells by active transport.
Insoluble starch is broken down into soluble malate by enzymes to lower water potential
Water enters by osmosis due to low water potential in cells.
The cells become turgid but the inner cell wall is thicker than the outer so they curve apart to form stomata.
How does the structure of the guard cells help in stomatal opening?
The inner cell wall is thicker than the outer cell wall therefore when the cells are turgid, they form kidney shapes and open the stomata.
Why do the stomata open in the day and close at night?
Day; allow gases and light in for photosynthesis
Night: Avoid loss of water vapour
What other factors affect stomatal opening?
What are the reasons for gas exchange in the leaf?
-meets photosynthetic needs
-water vapour loss maintains transpiration stream
-surplus 02 in the palisade mesophyll
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