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Biology A-level > Biology Chapter 6 > Flashcards

Biology Chapter 6 Flashcards

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1
Q

For efficient gas exchange, should surface area be comparatively small or large compared to its volume?

A

Large

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2
Q

Small organisms generally have relatively ____ surfaces compared with their volumes

A

Large

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3
Q

Large organisms have relatively ____ surfaces compared with their volumes

A

Smaller

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4
Q

Why is diffusion alone insufficient for the needs of many organisms?

A

Oxygen would take too long to diffuse through the organism

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5
Q

what are 2 ways organisms have overcome slow diffusion?

A
  1. Flattened, no cell far away from the surface

2. Specialised gas exchange organs

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6
Q

5 features of adapted exchange surfaces:

A
  1. Large surface area to volume ratio
  2. Very thin
  3. Partially permeable
  4. Movement of environmental medium
  5. Movement of internal medium
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7
Q

Why are specialised exchange surfaces located on the inside of the body?

A

They are thin and can be easily damaged

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8
Q

Gas exchange in single-celled organisms occurs by:

A

Diffusion

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9
Q

2 ways in which insects can reduce water loss:

A
  1. Waterproof covering

2. Small surface area to volume ratio

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10
Q

What are tracheoles:

A

Small branches of the trachea

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11
Q

What increases ventilation in insects?

A

Muscle movements

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12
Q

What are spiracles?

A

Tiny pores on the surface of the body

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13
Q

Describe 2 ways in which gases can move in and out of the tracheal system:

A
  1. Along a diffusion gradient, as oxygen is used up in respiration and carbon dioxide is produced. Therefore, oxygen moves in and carbon dioxide moves out
  2. Ventilation, aided by the movement of insect’s muscles
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14
Q

Why must insects be small in order for this system of gas exchange to function properly?

A

Short diffusion pathway

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15
Q

What is the name of the specialised gas exchange system in fish?

A

The gills

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16
Q

Where are the gills located?

A

Behind the head

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17
Q

What is the function of the gill lamellae?

A

To increase the gill surface area

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18
Q

What is the countercurrent flow?

A

Water if forced over the gill lamellae in the opposite direction to the way the blood flows through the lamellae

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19
Q

Why is the countercurrent flow important?

A

To ensure maximum possible gas exchange

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20
Q

Gas exchange in plants is similar to:

A

insects

21
Q

2 features of the plant gas exchange system:

A
  1. All cells close to external air

2. More rapid diffusion in the gas phase

22
Q

Adaptations for rapid diffusion in plants:

A
  1. Flat, thin shape
  2. Stomata
  3. Air space network in the mesophyll
23
Q

What are stomata?

A

Tiny pores, mainly distributed on the underside of the leaves

24
Q

What is the function of the guard cells?

A

To open and close the stomata

25
Q

Why is closing stomata important?

A

To prevent them from loosing too much water

26
Q

Suggest how the air spaces aid photosynthesis

A

Having spaces allows the carbon dioxide that enters through the stomata on the underside of the leaf to reach the palisade cell which are located nearest the sunlight. This allows an adequate supply of carbon dioxide for photosynthesis

27
Q

What are xerophytes?

A

Plants living in dry conditions that have developed adaptations to limit water loss

28
Q

Give 5 adaptations of xerophytes to reduce water loss

A
  1. Thick, waxy cuticle to form a waterproof barrier
  2. Rolling of leaves to reduce water potential gradient, so reduced evaporation and so transpiration
  3. Hairy leaves to reduce water potential gradient, so reduce evaporation and so transpiration
  4. Stomata in pits or grooves, so reduced evaporation and so transpiration
  5. Reduced surface area to volume ratio, so reduced evaporation that can tale place from the leaf, so reduces transpiration
29
Q

What is the structure of the trachea?

A

Flexible tube supported by cartilage. Walls are made of muscle, and epithelium is ciliated with goblet cells that provide mucus

30
Q

What is the function of trachea?

A

Provides a non-collapsible airway. Mucus traps dirt and microorganisms and is delivered to the throat

31
Q

What is the structure of the bronchi?

A

Two divisions of trachea. Similar in structure to trachea, supported by cartilage which reduces as the bronchi decrease in size

32
Q

What is the structure of the bronchioles?

A

Made of smooth muscle lined with epithelial cells - can constrict

33
Q

What is the function of bronchioles?

A

Control the air flow into and out of the alveoli

34
Q

What is the structure of the alveoli?

A

Stretchy air sacs of collagen and elastic fibres

35
Q

What is the function of the alveoli?

A

Main gas exchange surface

36
Q

An asthma attack involves constructing of the air passages. Which of the parts above would you expect to constrict the most and why?

A

Bronchioles, as they are made of muscle with little cartilage to support them

37
Q

What occurs when air pressure in the lungs is greater than air pressure outside?

A

Expiration

38
Q

Which 2 sets of muscles are involved in the mechanism of breathing?

A
  1. Diaphragm muscles

2. Intercostal muscles

39
Q

Relaxation of the internal intercostal muscles leads to:

A

Expiration

40
Q

Contraction of the external intercostal muscles leads to:

A

Inspiration

41
Q

Is inspiration active or passive?

A

Active

42
Q

What happens to the internal intercostal muscles while the external ones are contracting?

A

They relax

43
Q

Which 2 events increase the volume in the lungs?

A
  1. ribs move upwards and outwards

2. Diaphragm flattens

44
Q

How does increased lung volume affect pressure?

A

Decreases it

45
Q

Is expiration active or passive?

A

Largely passive

46
Q

What is the resting position of the diaphragm?

A

Dome-shaped

47
Q

What is the main cause of expiration during normal quiet breathing?

A

The elastic recoil from the tissue of the lungs

48
Q

which 2 factors can we measure to calculate pulmonary ventilation?

A
  1. Tidal volume

2. Ventilation rate

49
Q

How does oxygen move through the gas exchange system?

A

Trachea to the bronchi to the bronchioles to the alveoli down the pressure gradient to the alveolar epithelium to the capillary endothelium to the blood down the diffusion gradient

Biology A-level (14 decks)

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