Exchange - Surface Area To Volume Ratio And Gas Exchange Flashcards

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1
Q

Explain why large, multicellular organisms need specialised exchange surfaces and transport systems

A

Have smaller surface area to volume ratios
They cannot rely on simple diffusion across their surface alone to provide

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2
Q

Explain how exchange surfaces are specially adapted to facilitate gas exchange

A

Large surface area
Large concentration gradients
Short diffusion distance

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3
Q

Describe gas exchange in a single celled organism and relate features of exchange surfaces to the rate of diffusion

A

Simple organisms rely on simple diffusion for exchange of oxygen and carbon dioxide down their concentration gradients
Large surface area:volume ratio

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4
Q

Describe gas exchange in an insect

A
  1. Oxygen enters the insect through the spiracles and into the tracheae. Spiracle closes
  2. Oxygen diffuses through the tracheae into the tracheoles
  3. Oxygen is delivered directly to the tissues to be used for aerobic respiration
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5
Q

Relate the feature of gas exchange in an insect to the rate of diffusion (surface area)

A

Many narrow and branching tracheoles

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6
Q

Relate the feature of gas exchange in an insect to the rate of diffusion (concentration gradient)

A
  • some insects have rhythmic abdominal pumping,
  • some insects have air sacs,
  • aerobic respiration in cells means oxygen move from tracheoles into the cells + carbon dioxide moves from the cells to the tracheoles creating a concentration gradient
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7
Q

Relate the feature of gas exchange in an insect to the rate of diffusion (diffusion distance)

A

tracheoles branch into tissue next to cells respiring + the walls of the tracheoles are one squamous epithelial cell thick

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8
Q

Describe gas exchange in a fish

A

Mouth open:
- volume increases
- pressure decreases
- water flows through the mouth
Mouth closed:
- volume decreases
- pressure increases
- water flows over gills
- H20 flows through gill flap

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9
Q

Relate the features of gas exchange in a fish to the rate of diffusion (concentration gradient)

A

countercurrent flow

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10
Q

Relate the features of gas exchange in a fish to the rate of diffusion (surface area)

A

many gill lamallae

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11
Q

Relate the features of gas exchange in a fish to the rate of diffusion (diffusion distance)

A

capillaries in close proximity to lamellar walls, capillary walls and lamellar walls are one squamous epithelial cell thick

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12
Q

Describe gas exchange in a dicotyledonous plant

A

Diffusion of carbon dioxide:
- Carbon dioxide diffuses from the air spaces into the cells down a concentration gradient
- reduces the carbon dioxide concentration in the air spaces

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13
Q

Relate the features of exchange surfaces in a dicotyledonous plant to the rate of diffusion (surface area)

A
  • many small stomata
  • air spaces
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14
Q

Relate the features of exchange surfaces in a dicotyledonous plant to the rate of diffusion (diffusion distance)

A

Flat

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15
Q

Relate the features of exchange surfaces in a dicotyledonous plant to the rate of diffusion (concentration gradient)

A

-photosynthesis uses carbon dioxide and produces oxygen

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16
Q

Describe gas exchange in a human

A

Oxygen differs from the alveoli into the blood by:
- diffusing across the alveolar epithelium
- then through the capillary endothelium
- and then combines with haemoglobin in red blood cells

17
Q

Describe the countercurrent flow system

A
  • Water and blood flow in opposite directions
  • This maintains the concentration gradient of oxygen so oxygen concentration is always higher in water than in the blood along the whole length of the gill lamellar
  • So diffusion of oxygen occurs along the whole length of the gill lamellar
18
Q

Describe the process of ventilation (inhaling)

A

-external intercostal and diaphragm muscles contract
- ribcage mora upwards and outwards and diaphragm flattens
- thoracic cavity volume increases and pressure decreases
-air flows from the atmosphere to the lungs down a pressure

19
Q

Describe the process of ventilation (exhaling)

A
  • diaphragm muscles relax + internal intercostal muscles contract
  • ribcage moves downwards and inwards and diaphragm domes
    -thoracic cavity volume decreases and pressure increases
  • air flows from lungs to atmosphere down a pressure gradient
20
Q

Explain how insects limit water loss

A
  • waterproof exoskeleton
  • small surface area to volume ratio
21
Q

Relate features of exchange surfaces in a human to the rate of diffusion (diffusion distance)

A
  • alveolar walls = one squamous epithelial cell thick
  • capillary walls =one squamous endothelial cell thick
  • capillaries are in close proximity to the alveoli
22
Q

Relate features of exchange surfaces in a human to the rate of diffusion (concentration gradient)

A
  • circulation and blood supply removes oxygenated blood
  • ventilation replaces air in alveoli
  • elastic tissue removes deoxygenated air
23
Q

Relate features of exchange surfaces in a human to the rate of diffusion (surface area)

A
  • many narrow capillaries + many small alveoli
24
Q

Describe the adaptations of xerophytic plants to limit water

A
  1. Thick cuticle - stops water from leaving
  2. Hairy leaves - water vapour gets trapped in hairs and reduces water potential gradient
  3. Stomata in pits - water gets trapped and reduces water potential gradient
  4. Rolled leaves
  5. Leaves reduced to spines - reamed surface area for evaporation
  6. Reduced number of stomata