Exchange surfaces and breathing

Question 1

SA and V

Answer 1

• organisms exchange material with surroundings
• amount of material is proportional to volume
• amount of material its able to exchange is proportional to SA

Question 2

why do some organisms need specialised exchange surfaces?

Answer 2

they are multicellular, have a small SA:V ratio and a high metabolic activity

Question 3

SA definition

Answer 3

amount of tissue in contact with the environment

Question 4

SA and V of a sphere

Answer 4

SA - 4πr^2
V - 4/3πr^3

Question 5

features of specialised exchange surfaces

Answer 5

• large SA=overcomes limitations of SA:V in large organisms eg. villi and root hair cells
• thin layers=shortens diffusion distance eg. alveoli
• good blood supply/ventilation=maintans a (steep) conc. gradient for faster diffusion

Question 6

mass flow definition

Answer 6

movement of large volumes of substance within the transport system

Question 8

adaptations of the respiratory system in mammals

Answer 8

nasal cavity
- large SA with rich blood supply=keeps blood warm
- hairy lining with mucus (traps bacteria)
- moist surface (↑humidity=↓evaporation=air coming out of lungs loses less moisture)
trachea
- has incomplete rings of cartilage (prevents collapse+eases food passage)
- smooth muscle=contract/relax to constrict/dilate the airway and change airflow
- elastic tissue contains elastic fibres with elastin=allows stretching and recoiling
- ciliated epithelium=wafts mucus backwards towards stomach
goblet cells=secret mucus
bronchi
- reinforced with cartilage to keep the airway open
- smooth muscle can contract/relax to constrict/dilate the airway and change airflow.
- elastic tissue contains elastic fibres with elastin=allow stretching and recoiling
- lined with ciliated epithelial cells and goblet cells
bronchioles
- no cartilage=can change shape
- smooth muscle can contract/relax to constrict/dilate the airway change airflow
- elastic tissue contains elastic fibres with elastin=allow stretching+recoiling
alveoli
- one layer of epithelial cells=short diffusion pathway=rapid diffusion
- large SA=up rate of gas exchange
- partially permeable=only certain gases can diffuse across
- surrounded by dense network of capillaries=good blood supply=maintains conc. gradient
- ventilation=maintains steep diffusion gradient
- elastic fibres=stretching+recoiling
- collagen fibres=prevent alveoli from bursting+limits overstretching
- moist inner surface=gases can dissolve
- lung surfactant helps alveoli remain inflated

Question 9

ventilation definition

Answer 9

movement of air in and out of lungs

Question 10

ventilation in mammals

Answer 10

inspiration
- uses energy
- diaphragm contracts, flattens and lowers
- external int. contract - ribs up+out, internal int. relax
- ↑thoracic volume
- inside pressure<atmospheric=air enters

expiration
- x energy used
- diaphragm returns to og position
- external int. relax and internal int. contract - ribs in+down
- ↓thoracic volume
- inside pressure>atmospheric=air comes out

Question 11

vital capacity definition

Answer 11

the maximum volume of air that can be breathed in or out in one breath

Question 12

tidal volume definition

Answer 12

this is the volume of air that is breathed in or out during normal breathing (at rest)

Question 13

inspiratory reserve volume definition

Answer 13

the amount of air a person can inhale forcefully after normal tidal volume inspiration

Question 14

expiratory reserve volume definition

Answer 14

the amount of air a person can exhale forcefully after a normal exhalation

Question 15

residual volume definition

Answer 15

the volume of air left in the lungs after as much air has been breathed out as possible

Question 16

total lung capacity definition

Answer 16

the sum of the vital capacity and residual volume

Question 17

breathing rate definition

Answer 17

the number of breaths taken in one minute (one breath = taking air in and breathing it back out again)

Question 18

oxygen uptake

Answer 18

how much oxygen used by someone in a given time

Question 19

vent. rate definition

Answer 19

the amount of air that moves in and out of the lungs per minute

Question 20

vent. rate equation

Answer 20

vent rate=tidal vol x breathing rate

Question 21

characteristics of insects

Answer 21

• exoskeleton
• open circulatory system (body fluid acts as bld & tissue fluid)
• active living
• no bld. pigment (Hb) to carry O2

Question 22

how do insects breathe?

Answer 22

• air enters through spiracles (small in abdomen/thorax)=allow O2 to travel tracheae=narrow into trachieoles which have fluid over them

Question 23

why is there fluid over the trachieloe?

Answer 23

• up lactic acid when insect’s active=down water potential=tracheal fluid moves into insect’s body by osmosis=exposes large SA for gas exchange

Question 24

structure of insect’s ventilation system

Answer 24

• spiracles along abdomen+thorax allow air+water to enter
  may have sphincters.
• when they’re inactive: low O2 demand = spiracles closed
  (opposite when CO2 builds up)
• Spiracles lead to tracheae (widest) which carry air to body lined by chitin= keeps them open but impermeable to gases= X gas exchange
• Tracheae lead to tracheoles (elongated cell x chitin) throughout body tissues=allow gas exchange by diffusion
• At end of tracheoles = tracheal fluid limits air penetration

Question 25

adaptations fro gas exchange in insects

Answer 25

• Tracheoles - large SA gor gas exchange
• Oxygen dissolves in moisture on walls of tracheoles

Question 26

ventilation in large insects

Answer 26

• mechanical ventilation: air pumped in thoracic/ abdominal muscular movements
• Body vol. changes → pressure change in tracheae+trachieoles
• Collapsible enlarged trachea/air sacs act as reservoirs
• inflated/deflated by ventilation of thorax/abdomen

Question 27

Discontinuous gas exchange cycle insome insects.

Answer 27

Spiracles are in 3 states:
Open- C02=spiracles open to remove it + maximise gas exchange through pumping movements of thorax and abdomen
Flutter - spiracles open+close rapidly= moves. fresh air to renew O2 + minimises water loss
Closed- x gas exchange
O2 goes in dell by diffusion + CO2 moves out of body fluid where its held (buffering)

Question 28

bony vs cartilaginous fish

Answer 28

cartilaginous eg. shark. skate
- gills exposed to outside
- mouth on ventral side of head
- ram ventilation
- cartilage endoskeleton
- internal fertilisation (similar to humans)

bony eg. salmon, trout
- gills covered with operculum (gill cover)
- mouth at terminal end of head
- bony endoskeleton
- external fertilisation
(female lays egg, male releases sperm on top)

Question 29

why do fish need specialised adaptations?

Answer 29

• water=1000x denser than air & 100x more viscous than air
• oxygen content is lower than air
• unidirectional water flow to cope=down energy loss to move viscous low oxygen content water

Question 30

gills’ adaptations

Answer 30

• enclosed in gill cavity
• protected by operculum
• feathery=large SA
• good blood supply
• thin layer for gas exchange
• several layers=very efficient at extracting O2 from water

Question 31

structure of gills

Answer 31

• composed of 1000s of filaments=covered in lamellae (few cells thick+contain blood capillaries)=gives larger SA+short distance for gas exchange
• tips of gills (often) overlap=resistance=slows water movement for gas exchange

Question 32

large fish

Answer 32

• active= low SA:V=x enough to supply inner cells=continuous water flow over gills for exchange=slower than diffusion in air

Question 33

gas exchange in fish

Answer 33

• water+blood flow countercurrently=maintains conc. gradient=removes 80% of O2 in water

Question 34

ventilation mechanism in fish

Answer 34

• fish opens mouth=bucal cavity expands=↑SA for water intake+↓pressure in buccal cavity <external attmospheric pressure=water enters down a pressure gradient
• fish closes mouth=↑floor buccal cavity=↓vol+↑pressure=operculum cavity bulges out=↓pressure in it=water forced over gills