AQA Bio A Level Unit 3 Flashcards

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1
Q

Describe the relationship between size of organisms and volume and surface area (2)

A
  1. As organisms get bigger/their size increases;
  2. Their surface area to volume ratio decreases; (and vice versa)
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2
Q

Why don’t small organisms such as flatworms have gills or circulatory systems? (2)

A
  1. They are small enough;
  2. Their surface area to volume ratio is big enough that they can rely on diffusion through their body surface;
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3
Q

The bear species found towards the poles are the largest whereas the bear species found in the tropics are much smaller. Why? (3)

A
  1. Larger bears have a smaller surface area to volume ratio, and lose much less heat (per kg of bear).
  2. They are adapted to cold climates.
  3. Smaller bears lose too much heat could not survive in the extreme cold
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4
Q

Which cells make up the exchange surface in the lung? (2)

A

1.Alveolar epithelial cell;
2. Capillary endothelial cell;

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5
Q

Outline the route taken by air from the atmosphere to alveolus. (5)

A
  1. Mouth/nose
  2. Trachea
  3. Bronchi
  4. Bronchioles
  5. Alveolus
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6
Q

Outline the processes required for inspiration (breathing in)

A
  1. Contraction of external intercostals moves ribcage upwards and outwards;
  2. Diaphragm contracts and moves downwards from domed to flattened shape;
  3. Volume of thorax increases;
  4. Pressure decreases below atmospheric;
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7
Q

Breathing out can be passive (no muscle contraction required). Which feature of lung tissue allows this?

A
  1. Its elasticity/elastic recoil
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8
Q

What is pulmonary ventilation a measure of?

A

The volume of air breathed in one minute.

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9
Q

How do you calculate pulmonary ventilation?

A

Multiply tidal volume by breathing rate.

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10
Q

What is tidal volume?

A

The volume of air breathed in one breath.

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11
Q

Explain three ways in which fish gills are adapted to give efficient gas exchange. (3)

A
  1. Large number of lamellae and gill filaments give large surface area; 2. The exchange surface is just 2 flattened cells, reducing diffusion distance;
  2. Counter-current (of water and blood) maintains diffusion gradient.
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12
Q

Which cells make up the exchange surface in the fish gill? (2)

A
  1. Lamella epithelial cell;
  2. Capillary endothelial cell;
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13
Q

Outline the route taken by air from the atmosphere to insect cells? (3)

A
  1. Spiracles;
  2. Trachea;
  3. Tracheoles;
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14
Q

Describe and explain the advantage of the counter-current principle in gas exchange across a fish gill. (4)

A
  1. Water and blood flow in opposite directions;
  2. Maintains concentration gradient;
  3. Equilibrium not reached;
  4. Diffusion along length of lamellae;
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15
Q

Why might insects close their spiracles? (1)

A

To reduce water loss.

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16
Q

What causes insect spiracles to open? (1)

A

A build up of carbon dioxide (from cellular respiration).

17
Q

In some insects, their wing muscles compress tracheoles when they contract. What is the effect of this? (2)

A
  1. It has the effect of squeezing air out of tracheoles, and then drawing fresh air in;
  2. This maintains the concentration gradient;
18
Q

What is the effect of anaerobic respiration on gas exchange system in insects? (3)

A
  1. Anaerobic respiration produces lactic acid in cells;
  2. This lowers the water potential of the cells and some of the water in the ends of the tracheoles moves into the cells by osmosis;
  3. The surface area for diffusion is increased;
19
Q

Why might plants close their stomata? (1)

A

To reduce water loss.

20
Q

Can plants close their stomata and also photosynthesise? Why? (2)

A
  1. No.
  2. They can’t photosynthesise without gas exchange.
21
Q

What feature of leaves increases the surface area for diffusion into photosynthesising cells? Explain. (2)

A
  1. Air spaces;
  2. Provides short diffusion pathway - the air is in the spaces right outside the cells (rather than outside the whole leaf)
22
Q

Explain three ways in which lungs are adapted to give efficient gas exchange. (3)

A
  1. Large number of alveoli give large surface area;
  2. The exchange surface is just 2 flattened cells, reducing diffusion distance;
  3. Ventilation and circulation maintain the concentration gradient;