4.1 + 4.3 Flashcards
why do organisms need a mass transport system and specialised gas
exchange surfaces as they increase in size.
to satisfy demands from increased activity levels
features of gas exchange system 5
large sa
short diffusion pathway SDP
moist
permeable
mechanism to maintain diffusion gradient
how r insects adapted for gas exchange
- spiracles = tiny wholes - control air entering body, prevent water loss
- trachea branching into many smaller tubes - tracheoles - highly branched = large SA:V
- tracheoles = thin walls
- air sacs - provide larger SA for gas exchange
- conc gradient maintained = spiracles open and close to maintain balance of O2, CO2
how r fish adapted for gas exchange
- filaments covered in MANY lamella - increased SA
- many blood capillaries
- thin surface layer - SDP
- COUNTER-CURRENT MECHANISM - maintains conc gradient
what is ventilation mechanism in bony fish
- fish open mouth and lower floor of buccal cavity so vol in BC increases and so P decreases
- P increases in mouth of fish so water flows into BC, fish raise floor of BC to close mouth - increase P in BC
- water flows from BC -> gill cavity so P in GC increases
- operculum forced open + water leaves fish, operculum closed when BC floor lowered
what do cartilaginous fish depend on
- shark/rays
- no cintercurrnt mechanism as no operculum so dependsd on maintaining constant flow of water over gills
how is human gas exchange system adapted
- nasal cavity = moist - gases dissolve
- alveoli = 1 cell thick, permeable wall, SDP, each alveolus lined w moisture
- alveoli r surrounded by capillary network which r also 1 cell thick
- lungs are surrounded by pleural membrane that secrete pleural fluid and this skippering allows lungs to inflate + deflate easily w/o rubbing on ribs
breathing mechanism in humans
contraction of external intercostal + diaphragm increase vol of chest cavity so lower P than P of air outside so air flows into thorax - lungs inflate
muscles relax - breath out
CONTRACT = BREATH IN
RELAX = BREATH OUT
how r flowering plants adapted for gas exchange
- permeable - stomata
- large SA - very wide + irregular shaped spongy mesophyll cells so air sacs bw them
- SDP - thin + cells close to surface
- moist = surface of spongy mesophyll
how to open stomata
K+ ions moved into guard cells by AT which reduce water potential so water moves into guard cells by O and guard cells swell - increases turgor pressure, stomatal pores open due to uneven bending
what r lenticels
loosely arranged cells w many air sacs that connect inner tissue beneath abrk w outer world
