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A-Level Biology AQA > 3. Exchange and Transport (incomplete) > Flashcards

3. Exchange and Transport (incomplete) Flashcards

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1
Q

do larger animals have a smaller or larger surface area to volume ratio?

A

larger animals have a smaller surface area to volume ratio

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2
Q

do smaller animals have a smaller or larger surface area to volume ratio?

A

smaller animals have a larger surface area to volume ratio

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3
Q

why is diffusion across the outer membrane too slow in large multicellular organisms?

A
  • because there is a lot of cells deep within the body, and there is a big difference between them and the outside environment
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4
Q

what do larger animals have that prevents them from having to use diffusion to absorb and secrete substances?

A

speciallised exchange organs

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5
Q

what is it called when an animal has an efficient system to carry substances to and from cells?

A

mass transport

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6
Q

what does metabolic activity inside cells create? + what is metabolism?

A

heat
- the sum of all the chemical reactions happening in the body at that moment

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7
Q

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

A

its surface area

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8
Q

if an organism has a larger volume, they will have a ____ surface area

A

smaller

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9
Q

does having a smaller surface area make it easier or harder for an organism to lose heat from its body?

A

harder

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10
Q

if an organism has a smaller volume, its surface area is usually very ____

A

large

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11
Q

does having a larger surface area make it easier or harder for an organism to lose heat from its body?

A

easier

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12
Q

why do smaller organisms need a higher metabolic rate?

A

because they have a large surface area to volume ratio, and therefore lose heat very quickly. so they need a higher metabolic rate to generate enough heat to stay warm.

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13
Q

mammals such as mouses and horses are able to maintain a constant body temperature. use your knowledge of surface area to volume ratio to explain the higher metabolic rate of a mouse compared to a horse

A

mouses are smaller than horses so have a larger surface area to volume ratio. this means they have a faster rate of heat loss. so, they need to have a higher metabolic rate to generate heat, and replace the heat they lose.

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14
Q

why will organisms with a high surface area to volume ratio lose more water?

A

because more can evaporate from its surface

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15
Q

how can animals living in hot climate prevent excessive water loss if they have a large surface area to volume ratio?

A
  • kidney adaptations so they produce less urine
  • staying in the shade
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16
Q

how do small animals living in cold regions support metabolic rates? + how do they maintain body temperature?

A

they can eat high energy foods such as seeds and nuts
- have thick layers of fur or they hibernate

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17
Q

how do larger animals (small surface area to volume ratio) living in hot conditions lose heat?

A
  • some have large ears to increase their surface area, allowing them to lose more heat
  • some spend lots of time in water eg hippos, which helps them lose heat
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18
Q

describe how the human gas exchange system is structured + the flow of oxygen

A
  • air moves into the trachea as we breathe in
  • the trachea splits into two bronchi, and each bronchus leads into a lung
  • each bronchus then branches off into smaller tubes called bronchioles
  • the bronchioles end in small ‘air sacs’ called the alveoli where gases are exchanged
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19
Q

what does ventilation consist of? + what is it controlled by?

A
  • ventilation consists of inhalation and expiration
  • ventilation is controlled by the movement of the diaphragm, the internal and external intercostal muscles, and the ribcage
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20
Q

describe the process of inspiration

A
  • external intercostal muscles and diaphragm contract
  • this causes the ribcage to move upwards and outwards and the diaphragm to flatten
  • then, the volume of the thoracic cavity increases
  • as the volume of the thoracic cavity increases, lung pressure decreases below atmospheric pressure
  • so, as air moves from an area of high pressure to an area of low pressure, air flows down the trachea and into the lungs
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21
Q

is inspiration a passive or an active process?

A

it is an active process as it requires energy

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22
Q

describe the process of expiration

A
  • the external intercostal muscles and diaphragm relax, causing the ribcage to move downwards and inwards
  • this causes the diaphragm to become curved again
  • the volume of the thoracic cavity decreases, causing air pressure to increase above atmospheric pressure
  • so air is forced down the pressure gradient and out of the lungs
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23
Q

is normal expiration a passive or an active process?

A

its a passive process and does not require energy

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24
Q

describe what happens during forced expiration

A
  • the external intercostal muscles relax
  • the internal intercostal muscles contract, pulling the ribcage further down and in
  • the movement of both sets of intercostal muscles is antagonistic
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25
Q

what term is used to describe the relationship between both sets of intercostal muscles?

A

antagonistic.

26
Q

where is human gas exchange carried out?

A

in the alveoli

27
Q

what is the single layer on the surface of an alevolus called?

A

the alveolar epithelium

28
Q

what are some adaptations of the alveoli that enable efficient gas exchange to take place in humans?

A
  • alveolar epithelium is only one cell thick which provides a short diffusion distance
  • there is a huge number of alveoli in the lungs, which provides a large surface area for exchanging substances
  • the alveoli are surrounded by a network of capillaries, which maintains a good blood supply and decreases diffusion distance
  • steep concentration gradient between oxygen and carbon dioxide that increases the rate of diffusion
29
Q

how are oxygen and carbon dioxide exchanged in the alveoli?

A
  • oxygen diffuses out of the alveoli, across the alveolar epithelium and the capillary endothelium, and into the haemoglobin in the blood
  • carbon dioxide diffuses into the alveoli from the blood, and is breathed out
30
Q

what is the equation for pulmonary ventilation rate?

A

PVR = tidal volume x breathing rate

31
Q

is the surface area to volume ratio of a fish small or large

A

small

32
Q

is there more oxygen in water or in air? and by how much

A

there is thirty times more oxygen in air than in water

33
Q

how can the rate of diffusion be calculated?

A

using ficks law …
surface area x difference in concentration/length of membrane

34
Q

what are fish gills made up of?

A

stacks of gill filaments

35
Q

what is each gill filament covered in?

A

gill lamellae

36
Q

what are the gill lamellae in relation to each gill filament

A

perpendicular

37
Q

what part of the fish is the site of gas exchange

A

the lamellae

38
Q

describe the countercurrent flow principle and explain its importance in the fish gas exchange system

A

water flows over the gills in the opposite direction to the flow of blood in the capillaries

-this ensures equilibrium is not reached, and that a diffusion gradient is maintained across the entire length of the lamellae

39
Q

what are the adaptations of the fish gas exchange system

A
  • a large surface area to volume ratio, created by the stacks of gills, the gill filaments, and the lamellae
  • a short diffusion distance for TWO reasons

-the lamellae are very thin

-inside each lamellae, there is a capillary network

  • a maintained concentration gradient provided by the countercurrent flow principle
40
Q

what are the two features that all gas exchange surfaces have in common?

A
  • they have a large surface area
  • theyre thin to provide a short diffusion pathway across the gas exchange surface
41
Q

how does gas exchange occur in single celled organisms?

A

they absorb and release gases by diffusion through theyre outer surface
- they have an extremely large surface area and a thin surface which provides a short diffusion pathway
- therfore, there is no need for a gas exchange system

42
Q

what is the name of the gas exchange system in insects?

A

the tracheal system

43
Q

what are spiracles?

A

round openings that run along the length of the abdomen in insects
- oxygen enters through these holes and carbon dioxide leaves through them

44
Q

what are the trachea?

A
  • air filled pipes that receive oxygen from the spiracles and branch into tracheoles
45
Q

what are tracheoles?

A

branches of the trachea that deliver oxygen to respiring cells in insects

46
Q

describe how the insect gas exchange system transports oxygen to respiring tissues

A
  • oxygen moves into the spiracles by diffusion
  • oxygen then diffuses through the trachea, and these branch off into tracheoles
  • tracheoles then transport oxygen to cells by moving down a concentration gradient
47
Q

what are the adaptations of the insect gas exchange system?

A
  • tracheoles are highly branched so there is a larger surface area for the diffusion of oxygen
  • tracheole walls are thin so there is a shorter diffusion pathway and oxygen can diffuse into cells faster
48
Q

describe 3 ways in which the insect gas exchange system reduces water loss

A
  • insects have a waxy cuticle and a waterproof exoskeleton to limit water loss
  • spiracles have valves that can open and close to reduce water loss
  • spiracles have hairs that trap water molecules, decreasing the water potential gradient and thus the rate of water loss/evaporation
49
Q

starting from top layer to bottom layer, name the layers in the cross section of a leaf

A

waxy cuticle
(upper epidermis)
palisade mesophyll
spongy mesophyll
stomata and guard cells
(lower epidermis)

  • vasular bundle containing xylem and phloem vessels in the middle
50
Q

what reaction do plants need carbon dioxide for?

what reaction do plants need oxygen for?

A
  • photosynthesis
  • respiration
51
Q

what are the stomata?

A

the gap between two guard cells that open and close to allow gas exchange

52
Q

what is the vascular bundle?

A

where the xylem and phloem are

53
Q

what substance diffuses out of the stomata? what substance diffuses into the stomata?

A

oxygen
carbon dioxide

54
Q

when do stomata open?

A
  • during the daytime to allow gas exchange
  • during the day, water enters the guard cells, making them turgid and causing the stomata to open
55
Q

when do stomata close?

A

at night when photosynthesis wouldnt be occurring as there is no sunlight.
- the plant starts to get dehydrated, so the guard cells lose water and become flaccid, causing the stomata to close.

56
Q

what are xerophytic plants?

A

plants that are adapted to survive in environments with limited water (warm/dry/windy)

57
Q

name 8 adaptations of xerophytic plants

A
  • curled leaves to trap moisture and increase local humidity which reduces water potential gradient
  • hairs on epidermis to trap moisture around stomata which increases local humidity and decreases water potential gradient
  • sunken stomata to trap moisture, increasing local humidity and decreasing water potential gradient
  • small leaves to reduce surface area for transpiration to occur, reducing water loss
  • long roots to take water from deep in the ground
  • short roots to quickly absorb rainfall
  • less stomata so fewer places for water to escape
  • thicker waxy cuticle to reduce evaporation
58
Q

explain why water cannot evaporate directly from the surface of a leaf (1)

A
  • leaves are covered in waxy cuticle
  • waxy cuticle is hydrophobic
  • water is polar molecule so repelled by wax and cannot pass through waxy layer
59
Q

palisade cells are the main site for photosynthesis. explain one way in which palisade cells are adapted for photosynthesis. (2)

A
  • contain lost of chloroplasts that contain chlorophyll which absorbs light for photosynthesis.
60
Q

outline the steps you would take to calculate stomatal density

A
  • work out the area of the field of view
  • count the number of stomata in the field of view
  • factor to work out how many stomata per unit of area

A-Level Biology AQA (7 decks)

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