Gas exchange 2

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  • Created by: Hindleyc
  • Created on: 01-06-18 12:53
What is there very little of in water?
Dissolved oxygen
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What have fish developed?
Specialised gas exchange organs called gills which are composed of 1000s filaments
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What does each gill arch (4 each side of head) have?
2 Rows of filaments
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What is each filament flattened with?
An upper and lower row of lamellae (gill plates)
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What are lamellae?
Only a few cells thick covered in thin layer of epithelial cells, in close contact with those of neighbouring filaments, contain capillaries- excellent blood supply
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What do the tips of filaments do?
Overlap forming sieve like structure that provides resistance to flow of water and inc time for gas exchange
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What are gill slits?
Spaces between gill arches
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What is the operculum?
Bond flap that covers gills in operculum cavity which protects gills and aids ventilation
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What does the gill structure give?
Large SA and short distance for gas exchange
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What happens when fish opens mouth?
Opercular valve closes, Volume increases, Pressure decreases so water is drawn in (lower floor of buccal cavity)
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What happens when fish closes mouth?
Volume decreases, pressure increases, Opercular valve opens and water moves out flowing over gills and out through opercular valve behind gills
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What does it mean that the gills are thin?
Cannot support themselves w/o water
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How do the gills have a large SA?
Each gill has several arches that support many gill filaments. each filament has numerous lamellae which are flat structures equiv to alveoli
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How is a short d.d created?
Lamellae have very thin cells so there is short diffusing pathway b/w water and blood
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How is there an efficient blood supply?
Clever countercurrent system
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What is countercurrent?
2 substances flow through same body part in opposite directions
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In fish?
Blood in lamellae flows in opposite direction to water
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What happens?
Blood always meets water with a relatively lower concentration of dissolved oxygen
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What does this maintain?
Concentration gradient b/w blood and water for whole length of lamellae so 80% O2 in water can be extracted increasing efficiency of gas exchange
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How do some fish achieve this?
Swimming forward with mouth open
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What ensures continuous flow of water?
Co ordinated activity of both chambers
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What do slow swimmers/ fish in still water use?
Pumping system to move water
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What do plant cells do all the time? When illuminated? so what do they need to do?
Respire. Plant cells containing chloroplasts also photosynthesise so need to exchange gas
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Main function of a leaf? What does this require?
Photosynthesis- light co2 and water
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What happens at low intensity light?
CO2 given out due to respiration
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What happens as light intensity increases?
P/S begins so some co2 used up so less released
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What is the compensation point?
When co2 uptake = output
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What happens with a further increase of light?
CO2 taken up to fuel photosynthesis
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What happens at max rate of p/s?
Co2 uptake levels off
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What is water delivered by?
transpiration stream
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Adaptations of leaf?
Large flat surface to absorb max light. Thin- short d.d for gases to reach mesophyll cells and veins to support thin blade
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What is the upper epidermis?
Close fitting cells with waxy cuticle to reduce water loss- minimal stomata and few chloroplasts to allow light transmission
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What is the palisade mesophyll?
Long cylindrical cells perpendicular to surface packed with chloroplasts for max light absorption. Air spaces b/w cells for effective gas exchange . Moist cell walls to allow gases to dissolve
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What is the spongy mesophyll?
Large air spaces for uninterrupted diffusion of gases between stomata and palisade. Large SA exposed for gas exchange, moist cell walls to allow gases to dissolve
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What is the lower epidermis?
Thinner waxy cuticle and many stomata- 1000's per cm2
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What is the stomata?
Pores flanked by guard cells that contain some chloroplasts
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What are guard cells?
Specialised epidermal cells (only ones with chloroplasts) kidney shaped and change in shape to open and close stomatal pore
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What is stomatal control?
Balance between requirements for photosynthesis and water loss
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What do the leaves need co2 for? why is this a problem?
Photosynthesis, water evaporates through open stomata
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What do stomata open and close according to?
External conditions and needs of the plant
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How do stomata open and close?
If water enters guard cells become turgid and size of cell increases- can't expand width ways so forced to elongate- fixed at each end so bow outwards creating stomatal pore
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What happens in light?
ATP used to actively pump K+ ions into guard cells creating water potential gradient so water is drawn into the cells by osmosis and guard cells become turgid
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What happens in dark?
Less ATP so pumping stops and ions leak out of cells, water leaves by osmosis along gradient and cells become less turgid and stomatal pore closes
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How do plants close stomata during daylight if they have a lack of water?
A lack of water increase activates a potassium pump in the opposite direction- water follows and turgor is reduced closing the pore
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Other cards in this set

Card 2

Front

What have fish developed?

Back

Specialised gas exchange organs called gills which are composed of 1000s filaments

Card 3

Front

What does each gill arch (4 each side of head) have?

Back

Preview of the front of card 3

Card 4

Front

What is each filament flattened with?

Back

Preview of the front of card 4

Card 5

Front

What are lamellae?

Back

Preview of the front of card 5
View more cards

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