3. Exchange and Transport (incomplete)

Question 1

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

Answer 1

larger animals have a smaller surface area to volume ratio

Question 2

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

Answer 2

smaller animals have a larger surface area to volume ratio

Question 3

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

Answer 3

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

Question 4

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

Answer 4

speciallised exchange organs

Question 5

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

Answer 5

mass transport

Question 6

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

Answer 6

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

Question 7

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

Answer 7

its surface area

Question 8

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

Answer 8

smaller

Question 9

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

Answer 9

harder

Question 10

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

Answer 10

large

Question 11

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

Answer 11

easier

Question 12

why do smaller organisms need a higher metabolic rate?

Answer 12

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.

Question 13

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

Answer 13

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.

Question 14

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

Answer 14

because more can evaporate from its surface

Question 15

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

Answer 15

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

Question 16

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

Answer 16

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

Question 17

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

Answer 17

• 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

Question 18

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

Answer 18

• 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

Question 19

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

Answer 19

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

Question 20

describe the process of inhalation

Answer 20

• 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

Question 21

is inspiration a passive or an active process?

Answer 21

it is an active process as it requires energy

Question 22

describe the process of expiration

Answer 22

• 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

Question 23

is normal expiration a passive or an active process?

Answer 23

its a passive process and does not require energy

Question 24

describe what happens during forced expiration

Answer 24

• 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

Question 25

where is human gas exchange carried out?

Answer 25

in the alveoli

Question 26

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

Answer 26

the alveolar epithelium

Question 27

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

Answer 27

• 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
• steep concentration gradient between oxygen and carbon dioxide that increases the rate of diffusion

Question 28

how are oxygen and carbon dioxide exchanged in the alveoli?

Answer 28

• 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

Question 29

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

Answer 29

small

Question 30

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

Answer 30

there is thirty times more oxygen in air than in water

Question 31

how can the rate of diffusion be calculated?

Answer 31

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

Question 32

what are fish gills made up of?

Answer 32

stacks of gill filaments

Question 33

what is each gill filament covered in?

Answer 33

gill lamellae

Question 34

what are the gill lamellae in relation to each gill filament

Answer 34

perpendicular

Question 35

what part of the fish is the site of gas exchange

Answer 35

the lamellae

Question 36

what are the adaptations of the fish gas exchange system

Answer 36

• 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

Question 37

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

Answer 37

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