Gas exchange Flashcards
State two important structural features of alveoli (2)
- one cell thick
- large surface area
- large number of capillaries
Briefly explain how inspiration is brought about (2)
- contraction of intercostal muscles and diaphragm
- increased volume and decreased pressure so air moves into lungs
Describe three features of fish gills allow them to acheive efficient gas exchange (3)
- large surface area
- thin - short diffusion pathway
- permeable
- good blood supply
Water is a dense medium with a low oxygen content. Explain how bony fish overcome problems of oxygen uptake in water (4)
- water forced over fill by pressure differences
- one way flow
- counter current flow of blood and water
- concentration gradient maintained over entire gill surface
- high affinity of haemoglobin
Explain why large mult cellular organims have evolved special surfaces for gas exchange (3) descibe and explain how terrestrial animals are adapted for gas exchange (7)
- metabolic needs are larger organisms need more oxygen
- external surface insufficient for gas exchange
- diffusion proportional to surface area
- SA:V is to small
- diffusion distances are large
- not enough O2 can diffuse
- large number of alveolus increase surface area
- reduce heat loss/ water loss
- internal lungs
- gas exchange take place in alveoli
- thin walls - short diffusion pathway
- moisture allow gases to dissolve
- blood capillaries maintain concentration gradient between air and body
- heamoglobin transsport of oxygen
- replace stale air with fresh air
Describe and explain the process of inspiration in a mammal (4)
- intercostal muscles contract and ribs move up and out
- diaphragm contract and diaphragm flattens
- internal volume of thorax increases
- pressure in lungs decreases
- higher air pressure outside forces air into lunds
Explain how counter current flow works in gills of bony fish (4)
- blood flows across gills in opposite direction to water
- water always has more oxygen than blood
- oxygen passes from water into blood
- across entire gill
Explain why parallel flow is less effeicient than counter current flow (2)
- equilibrium is reached part way across gill
- less oxygen uptake
Suggest why gill filaments would not provide an effient gas exchange surface on land (2)
- gills dry out prevents oxygen from dissolving on surface of skin
- fills may collapse decrease of surface area
Describe three properites that all respiratory surfaces musst possess and why (3)
- thin - short diffusion pathway
- large surface area - for gas exchange
- moist - allow gases to dissolve
- permeable - allow gases to pass through
Give two reasons why gilld do not function effectivley on land (2)
- they dry out
- they clump together and collapse
Define counter current flow as seen in gilld of bony fish and explain why counter current flow is more efficient (3)
- blood flows in opposite direction to water
- concentration gradient is maintained across whole urface
- greater concentration of oxygen in blood is achieved
Bony fish relies on gills for gas exchange explain how the prescenece of gill filaments is an adpatation to gas exchange (2)
- increase surface area
- diffusion takes place
Describe the process of ventilation in bony fish (4)
- buccal cavity lowered
- volume buccal cavity increases pressure decreases
- water pulled in from outside
- mouth closes and buccal cavity raises
- water forced into gills
- pressure in gill cavity increases
- forces open operculum
Suggest why muscle fibres do not exceed a large diameter (2)
- diffusion pathway would be to lond
- speed up diffusion
Describe the change in fluid level in tracheoles during flight and suggest how this changes benefits of gas exchnange during flight (2)
- less fluid
- more area for gas exchange
Suggest how marram grass is adapted with it’s distribution of stomata to conserve water (3)
- less stomata
- rolles upper epidermiss face inwards
- no stamate on lower surface
Give two structural adaptation shown by marram grass help it to survive in dry conditions (2)
- waxy cuticle on lower surface
- reduced leaf surface area
- sunken stomata
- hairs
- long roots
Describe how bony fish ventialtes it gills and absorbs oxygen from water
- water forced over gill
- by pressure changes
- action of mouth and operculum
- water flows in opposite direction to blood/counter current flow
- maintains concentration gradient across whole gill
- as blood always meet water with high oxygen concentration
- equilibrium is never reached
Describe four similiarities in the adaptations of gill for gas exchange and mamalian villi for absorption of digested products (4)
- large surface area
- large network of capillaries
- thin
- moist
- short diffusion pathway
Describe how the gills of both bony fish and axolotl are adapted to increase efficiency of gas exchange and explain how structures in heads of bony fish enable them to be highly active even why oxygen levels are relativley low but axolytuls are slower moving under these conditions (9)
- large surface area due prescence of gill filaments
- permeable
- rich blood supply to maintain concentration gradient
- reduce diffusion distance
- seperate buccal and opercular cavities
- opercular close gill cavity
- lower floor buccal cavity increases volume and decreases pressure in buccal cavity
- mouth opens and water enters
- mouth closes floor of buccal cavity is raised
- increases pressure forces water over gils
- counter current flow
- maintain concentration gradient for oxygen across whole gill surface
- oxygen absorption more effiecient
- axolotls have external gills so no ventilation mechanism
- paralllel flow
- less effiecient as oxygen absorbtion needed for aerobic respiration
Define the term diffusion (1)
- the movement of molecules from a higher to lower concentration
Explain why simple diffusion is adequate in flatworms (2)
- long flattened shape large surface area to volume ration
- very short diffusion pathway