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

3. Exchange and Transport (incomplete) Flashcards

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
what term is used to describe the relationship between both sets of intercostal muscles?
antagonistic.
26
where is human gas exchange carried out?
in the alveoli
27
what is the single layer on the surface of an alevolus called?
the alveolar epithelium
28
what are some adaptations of the alveoli that enable efficient gas exchange to take place in humans?
- 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
how are oxygen and carbon dioxide exchanged in the alveoli?
- 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
what is the equation for pulmonary ventilation rate?
PVR = tidal volume x breathing rate
31
is the surface area to volume ratio of a fish small or large
small
32
is there more oxygen in water or in air? and by how much
there is thirty times more oxygen in air than in water
33
how can the rate of diffusion be calculated?
using ficks law ... surface area x difference in concentration/length of membrane
34
what are fish gills made up of?
stacks of gill filaments
35
what is each gill filament covered in?
gill lamellae
36
what are the gill lamellae in relation to each gill filament
perpendicular
37
what part of the fish is the site of gas exchange
the lamellae
38
describe the countercurrent flow principle and explain its importance in the fish gas exchange system
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
what are the adaptations of the fish gas exchange system
- 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
what are the two features that all gas exchange surfaces have in common?
- they have a large surface area - theyre thin to provide a short diffusion pathway across the gas exchange surface
41
how does gas exchange occur in single celled organisms?
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
what is the name of the gas exchange system in insects?
the tracheal system
43
what are spiracles?
round openings that run along the length of the abdomen in insects - oxygen enters through these holes and carbon dioxide leaves through them
44
what are the trachea?
- air filled pipes that receive oxygen from the spiracles and branch into tracheoles
45
what are tracheoles?
branches of the trachea that deliver oxygen to respiring cells in insects
46
describe how the insect gas exchange system transports oxygen to respiring tissues
- 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
what are the adaptations of the insect gas exchange system?
- 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
describe 3 ways in which the insect gas exchange system reduces water loss
- 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
starting from top layer to bottom layer, name the layers in the cross section of a leaf
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
what reaction do plants need carbon dioxide for? what reaction do plants need oxygen for?
- photosynthesis - respiration
51
what are the stomata?
the gap between two guard cells that open and close to allow gas exchange
52
what is the vascular bundle?
where the xylem and phloem are
53
what substance diffuses out of the stomata? what substance diffuses into the stomata?
oxygen carbon dioxide
54
when do stomata open?
- 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
when do stomata close?
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
what are xerophytic plants?
plants that are adapted to survive in environments with limited water (warm/dry/windy)
57
name 8 adaptations of xerophytic plants
- 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
explain why water cannot evaporate directly from the surface of a leaf (1)
- 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
palisade cells are the main site for photosynthesis. explain one way in which palisade cells are adapted for photosynthesis. (2)
- contain lost of chloroplasts that contain chlorophyll which absorbs light for photosynthesis.
60
outline the steps you would take to calculate stomatal density
- 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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