Adaptations in gas exchange

Question 1

What is surface area to volume ratio

Answer 1

• organisms exchange gases eg oxygen and carbon dioxide with the atmosphere via a gas exchage surface
• surface area determines how much gas can me exchanged
• organims increase in size a specialised gas exchange surdace is required to increase area available
• increase area for water loss tjere always balance to be struck between exchanging gases and water loss in terrestial organisms

Question 2

What are characteristics of gas exchange surface

Answer 2

• large surface area to volume ratio
• moist to allow gases to dissolve
• thin provide short diffusion distance
• permeable to gases

Question 3

Describe the gas exchange surface of unicellular organisms

Answer 3

• eg amoeba surface area is large to meet needs of organisms therefore materials can be exchange directly across thin and permeable cell surface membrane
• cytoplasm constanly moving concentration gradient always maintained

Question 4

Describe the gas exchange surface of multiceelular organisms

Answer 4

• large organisms surface area to volume ration decreases so diffusion is insufficient
• number adaptations solved more specialised larger the organism
• animals are very active so they have a higher metabolic rate oxygen requirements not met by body surface area
• prescence specialissed gas exchange ssurface with ventilation mechanism concentration gradient maintained across respiratory surface

Question 5

Describe the gas exchange surface of terrestrial animals

Answer 5

• one consequence maintaining moist respiratory surfaces is water loss
• internal gas exchange surfaces called lungs

Question 6

Describe the gas exchange surface of reptiles eg snakes and crocodiles

Answer 6

• internal lungs
• more complex large surface area

Question 7

Describe the gas exchange surface of a flatwork

Answer 7

• flattened body reduce diffuion distance between surface and cells inside increase overall sufrace area

Question 8

Describe the gas exchange surface of an earthworm

Answer 8

• secrete mucus to maintain moist surface has a well developed capillary network under skin
• low metabolic rate reduce oxygen requirements
• network of blood rvessel and blood containing haemoglobin for transport of oxygen
• carbon dioxide transported largely in blood plasma

Question 9

Describe the gas exchange surface of amphibians eg frogs and newts

Answer 9

• moist and permeable skin with well developed capillary network beneath surface
• lungs used when more active

Question 10

Describe the gas exchange surface of birds

Answer 10

• flight generates high metabolic rate hence oxygen requirements
• efficient ventilation mechanism is to increase concentration gradient across lung surface

Question 11

Describe the gas exchange surface of fish

Answer 11

• specialised internal gas exchange surface called fills made of numerous gill filaments containing gill laellae at right angles to filaments
• increase surface area for exchange of oxygen and carbon dioxide

Question 12

What are cartilegenous fish eg sharks

Answer 12

• blood and water flow in the same direction over gill (parallel flow)
• only possible over part of gill filament surface as equilibrium is reached
• prevent further diffusion and reduces oxygen that can be absorbed in blood
• ventilation mechanism is basic open mouth allow water to pass over gills

Question 13

What is counter current flow eg bony fish

Answer 13

• blood and water flow in opposite directions
• more effiecient system diffusion maintained along entire length of gill filaments as always has a higher concentration gradient in water than in the blood it meets
• higher oxygen absorbtion as equilibrium not reached
• bondy fish more advances ventilation mechanism than cartliegenous fish

Question 14

how does ventilation occur in bondy fish

Answer 14

• bony fish have an internal body skeleton and flap covering gills called operculum

Question 15

How does water move into mouth in bony fish

Answer 15

• mouth open
• floor of buccal cavity lowers
• water rushes in
• opercular valve closed
• volumer increases pressure drops

Question 16

How does water move out of bony fish

Answer 16

• mouth close
• flow or uccal cavity rises
• water forced out over gills
• opercular valve open
• volume decreases pressure increases

Question 17

What are structure of the lungs

Answer 17

• trachea is supported by 20 incomplete cartilegenous rings, branches into two bronchi entering a lung
• bornchi branch into finer tubes called bronchioled finally ending in alveoli where gas exchange takes place

Question 18

Descrbie the process of inspiration (inhaling)

Answer 18

• active process
• external intercostal muscles contract moving ribs up and out pulls outer pleural membrane outwards
• diaphragm contracts and flattens
• reduces the pressure in the pleaural cavity and inner pleural membrane moves outwards
• pulls on the surface of lungs causing alveoli to expand
• alveolar pressure decreases to below atmospheric pressure so air is drawn in

Question 19

Describe expiration (exhale)

Answer 19

• passive process
• external intercostal muscles relax so rib move downwards and inwards allowing the pleaural membrane to move inwards
• diaphragm relaxes and move upwards
• increases pressure in pleural cavity and inner pleaural membrane moves inwards
• pushes on the suface of the lungs and causes the alveoli to contract
• alevolar pressure increases to above atomspheric presure so air is forced out

Question 20

Describe gas exchange in alveoli

Answer 20

• very large surface area - 700 million alveoli
• very thin walls
• surrounded by capillaries short diffuion ditance and good blood supply
• moit lining
• permeable to fases
• collagen and elastic fibres allow expansion and recoil
• branch of pulmonary arter yvrubgs deoxygenated blood to the alveoli and a branch of pulmonary vein carries deoxygenated blood from alveoli back to the heart
• alveoli produce a surfactant which lowers the surface tenssion preventing alveoli from collapsing and sticking together and allow gases to dissolve elastic fibres and collagen

Question 21

Describe gas exchange in insects

Answer 21

• insects have branched chitin lined system of trachea with openings called spiracles
• chitin is arranges in rings allowing the trachea to expand and contract and act like bellows draing air in and out of inssects body
• spiracles found in pairs in segments if the thorax and abdoen close during inactivity and prescent of chitin help reduce water loss
• trachea tubes come into contact with every tissue suppluing oxygen and removing carbon dioxide so no need for haemoglobin
• ends of tubes are filled with fluid to allow gases to dissolve
• muscles in thorax and abdomen contract/relax causing rythmical movementss that ventilate the tracheoles tubes maintianing a concentration gradient

Question 22

Describe gas exchange in plants

Answer 22

• plants require oxygen for respiration and carbon dioxide for photosynthesis
• fase’s obtained by diffusion through the leaf
• hover to reduce water loss plant have a waxy cuticle covers surface of the leaf prevents diffusion of gases
• plants have stomata underside of mot leaves open during the daay aloow gas exchange close at night or during drought conditions to reduce water loss

Question 23

Describe the stomatal opening mechanism

Answer 23

• size of pore (stoma) between guard cells can be controlled to reduce water losss via transpiration by guard cells that surround it
• guard cell photoynthesis producing ATP
• energy releases from ATP activley transport potassium ions into guard cells
• triggers starch (insoluble) to be onverted into malate ions (soluble)
• water potential of guard cells is lowered so water eneters cells via osmosis
• guard cells expand and outer wall stretched more than inner wall because it’s thinner creates a pore betwee two guard cells
• reverse happens at night

Question 24

What are the adaptations for leafs in gas exchange

Answer 24

• leaves are thin and flat for providing a large surface area to capture light and for gas exchange
• leaves have many pores called sstomata (singular stoma) to allow gas exchange of gases
• spongy mesophyll cells are surrounded by air spaces that allow gases to diffuse

Question 25

Parallel flow

Answer 25

• blood and water flow in the same direction at the gill lamellae maintaining the concentration gradient for oxygen to diffuse into the blood only up to the point where its concentration in the blood and water is equal

Question 26

Counter current flow

Answer 26

• blood and water flow in opposite directions at the gill lamellae mainitaining the concentration gradient and therefore oxygen diffusion into the blood along their entire length

Question 27

Transpiration

Answer 27

• the evaporation of water vapour from leaves or other above ground parts of the plant out through the stomata into the atmosphere