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AQA A Level Biology 2018 > Exchange and Transport Systems > Flashcards

Exchange and Transport Systems Flashcards

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1
Q

What do cells need to take in?

A

Oxygen and nutrients.

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2
Q

What do cells need to excrete?

A

Waste products like carbon dioxide and urea.

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3
Q

What else do cells need to exchange?

A

Heat - as organisms need to stay at roughly the same temperature.

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4
Q

Smaller animals have a …

A

High surface area to volume ratio.

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5
Q

What can easily happen in a single celled organism?

A

Substances can directly diffuse in and out of cells - the rate is quick because of the small distances the substances have to travel.

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6
Q

What happens a bit more difficultly in a multicellular organisms?

A

Diffusion is too slow because some cells are deep within the body (big distance to travel) and they have a low surface area to volume ratio.

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7
Q

What does the rate of heat loss from an organism depend on?

A

It’s surface area - a small surface area makes it harder for it to lose heat from its body.

Large surface area = heat is lost more easily.

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8
Q

Animals with a compact shape have a…

A

Small surface area relative to their volume - minimising heat loss from their surface.

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9
Q

Animals with a less compact shape have…

A

A larger surface area relative to their volume - increasing heat loss.

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10
Q

Give 3 examples of behavioural/physiological adaptations of organisms to aid exchange:

A
  • smaller mammals may have thick layers of fur / hibernate when it’s really cold.
  • elephants have large flat ears to increase their SA allowing them to lose more heat (live in hot regions)
  • small mammals living in cold regions need to eat large amounts of high energy foods such as seeds and nuts.
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11
Q

Most Gas exchange surfaces have two things in common:

A
  • they have a large surface area.

- they’re thin = short pathway.

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12
Q

What gas exchange system do insects use?

A

Tracheal System

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13
Q

What are the tubes called in Insects?

A

Trachaea

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14
Q

Give the process through the Tracheae: (2)

A
  • air moves through pores called SPIRACLES (oxygen travels down concentration gradient)
  • tracheae branch into tracheoles which lead to individual cells.
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15
Q

How does carbon dioxide move out of the cells in insects?

A

Moves from the cells down its own concentration gradient towards the spiracles.

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16
Q

What do insects use to move air in and out the spiracles?

A

Rhythmic abdominal movements.

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17
Q

Give the process in which Gas Exchange happens in human lungs: (3)

A
  • air enters trachea which splits into two bronchi.
  • air goes into bronchioles.
  • air is in alveoli where gas exchange happens.
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18
Q

What is Ventilation?

A

Breathing in and out.

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19
Q

Breathing in is…

A

Inspiration.

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20
Q

Breathing out is…

A

Expiration.

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21
Q

Each alveolus is made from…

A

A single layer of thin, flat cells called alveolar epithelium.

22
Q

How are Alveoli adapted for Gas Exchange: (3)

A
  • thin exchange surface = short diffusion pathway.
  • large surface area = so many of them.
  • good blood supply = surrounded by a network of capillaries.
23
Q

How does Gas Exchange work in the Alveoli: (2)

A

Oxygen diffuses our of the alveoli (across alveolar epithelium and the capillary endothelium) and into haemoglobin in the blood

Carbon dioxide diffuses into the alveoli from the blood and is breathed out.

24
Q

What do fish use for Gas Exchange?

A

Gills

25
Q

What are Gills made up of?

A

Thin plates called Gil filaments - which give a big surface area for exchange of gases.

26
Q

What are Gil filaments covered with?

A

Lamellae - which increase the surface area even more.

27
Q

Give 2 features of the Lamellae:

A
  • lots of blood capillaries
  • thin surface area of cells

To speed up diffusion.

28
Q

What is the Counter-Current System?

A

Blood flows through the lamellae in one direction and water flows over in the opposite direction.

29
Q

What does the Counter-Current system do?

A

It maintains a concentration gradient between the water and the blood - the conc of oxygen is always higher in water than in the blood.

30
Q

Explain the process of Inspiration: (3)

A
  • external intercostal and diaphragm contract causing the rib cage to move UP AND OUTWARDS.
  • diaphragm flattens and there’s an increase in volume of the thoracic cavity.
  • as that volume increases, the lung pressure decreases.
31
Q

Air will always flow from… (human lungs)

A

An area of high pressure to an area of lower pressure (from atmospheric air)

32
Q

Is inspiration an active process?

A

Yes - it requires energy.

33
Q

Explain the process of Expiration: (3)

A
  • external intercostal and diaphragm muscled relax causing the rib cage to move DOWN and INWARDS.
  • diaphragm becomes curved again decreasing the volume of thoracic cavity causing the pressure to increase (to above atmospheric pressure)
  • air moves from lungs to outside air as the pressure is lower outside.
34
Q

Does expiration require energy?

A

No - it’s a passive process.

35
Q

How can expiration be forced?

A

E.g. to blow out candles.

36
Q

What happens during forced expiration? (2)

A

The external intercostal muscles relax and the internal intercostal muscles contract, pulling rib cage further down and in.

Movement of the two sets of intercostal muscles is said to be opposing.

37
Q

What is Tidal Volume?

A

The volume of air in each breath - usually between 0.4 - 0.5 dm cubed.

38
Q

What is Ventilation Rate?

A

The number of breaths per minute - usually 15.

39
Q

What is Forced Expiratory Volume?

A

The maximum volume of air that can be breathed out in 1 second.

40
Q

What is Forced Vital Capacity?

A

The maximum volume of air it is possible to breathe forcefully out of the lungs after a really deep breath in.

41
Q

Plants need CO2 for..

A

Photosynthesis and this produces oxygen as a waste gas. Then they need oxygen for respiration which produces carbon dioxide as a waste gas.

42
Q

Where do plants exchange gases?

A

On the surface of the mesophyll cells in the leaf - they have a large SA.

43
Q

How do gases move in and out the leaf?

A

Through special poles in the epidermis called stomata.

44
Q

What can the stomata do?

A

They can open to allow exchange of gases but also close if the plant is losing too much water.

45
Q

What controls the opening and closing of stomata?

A

Guard cells. And

46
Q

What do insects do if they are losing too much water? (2)

A

They close their spiracles using muscles.

They also have a waterproof waxy cuticle all over their body and tiny hairs around their spiracles which reduce evaporation.

47
Q

If a plant starts to get dehydrated…

A

Guard cells lose water and become flaccid which closes the pore.

48
Q

If a plant wants to open…

A

Water enters the guard cells making them turgid which opens the stomata.

49
Q

What are Xerophytes?

A

Plants which are specially adapted for life in warm, dry or windy habitats where water loss is a problem.

50
Q

Examples of Xerophytic adaptations: (3)

A
  • a layer of hairs on the epidermis to trap moist air around the stomata.
  • a reduced number of stomata so there are fewer places for water to escape.
  • waxy and waterproof cuticles on leaves and stems to reduce evaporation.

AQA A Level Biology 2018 (17 decks)

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