Gas exchange in animals (C3) Flashcards
What is the relationship between SA:V ration and size?
the surface area to volume ratio of organisms decreases as size increases
i.e the SA:V ration of an amoeba is larger than that of an elephant - a larger SA:V ration is more efficient
Gas exchange across a single celled organism; amoeba
amoeba is a single celled organism:
- which has a large surface area to volume ratio
- so gaseous diffusion through the cell membrane is fast and sufficient enough to meet its oxygen demands
Gas exchange across a simple multicellular organism; flatworm
flatworms are multicellular organisms:
- a smaller surface area to volume ratio than amoeba
- but are flattened to reduce diffusion distance providing a short diffusion pathway
- so can rely on their external surface for gas exchange, gases dissolve and diffuse across their membrane
Gas exchange across a simple multicellular organism; earthworm
earthworms are tubular:
- also rely on their external surface, gases exchange directly with the environment via diffusion across the moist surface
- but have a circulatory system to deliver oxygen to the tissues, blood vessels close to surface which gases diffuse in/out of
- circulating blood maintains a concentration gradient and contains contains the respiratory pigment hb
Adaptations of a respiratory surface to achieve maximum rate of diffusion
- THIN - short diffusion pathway
- MOIST - gasses can dissolve and diffuse
- LARGE SA - diffusion across surface
- PERMEABLE - to gases
Why do larger complex organisms need a ventilating mechanism?
large active animals have high metabolic rates thus need ventilating mechanisms to maintain gradients across respiratory surfaces
Why do larger complex organisms need specialised respiratory organs?
- SA:V ratio too small for simple diffusion to be sufficient to meet the needs of organism
- simple diffusion is too slow
- more metabolically active thus higher demand for oxygen
- tougher external surface so need internal moist gas exchange surfaces
What are the adapted respiratory surfaces to suit environmental conditions? fish? mammals?
- fish have gills for aquatic environments
- mammals have lungs for terrestrial environments
Gas exchange system in fish: problems, cartilaginous, bony?
problems:
• water contains LESS o2 than air
• SLOWER rate of diffusion
• a more DENSE medium
cartilaginous fish e.g shark:
• 5 gill clefts open at gill slits - water taken into MOUTH/buccal cavity, FORCED through GILL SLITS when flood of mouth is RASIED
• gas exchange involves PARALLEL flow - blood in gill capillaries circulates in SAME direction as water flowing over gills
bony fish e.g herring
• gills covered with flap - OPERCULUM
• gas exchange involves COUNTER CURRENT flow - blood in gill capillaries circulated in OPPOSITE direction as water flowing over gills
Anatomy of bony fish gills x4 and exchange between water as gas exchange surface
- OPERCULUM - flap over gills
- GILL ARCHES - support the gills
- GILL FILAMENTS - along gill arch, on each filament are the GILL LAMELLAE - providing a large surface area for gas exchange
*blood CIRCULATES through the gill LAMELLAE in the opposite direction to water flow creating a CONCENTRATTION GRADIENT across whole lamellae, OXYGEN in water DIFFUSES through gill lamellae into CAPILLARIES and CARBON DIOXIDE diffuses OUT into the WATER
What is the method of ventilation in bony fish?
water flows IN - inspiration
- mouth - open
- operculum - closed (one way current)
- floor of buccal cavity LOWERS - volume increase
- pressure decreases
water flows OUT - expiration
- mouth - closed
- operculum - open
- floor of buccal cavity RISES - volume decreases
- pressure increases - water forced out
Counter current flow vs parallel flow (efficiency: + - )
COUNTER CURRENT (bony fish) - opposite directions: • gradient for o2 diffusion into blood from water is MAINTAINED over WHOLE LENGTH of gill LAMELLAE \+ more EFFICIENT - results in a HIGHER o2 SATURATION level
PARALLEL FLOW (cartilaginous fish) - same directions: • gas exchange is efficient at FIRST as very STEEP oxygen CONCENTRATION GRADIENT - HALF WAY along gill lamellae, EQUILIBRIUM is reached and NO gradient thus diffusion and exchange of o2 and co2 is no longer possible
Structures of the human respiratory system x10
LARYNX - voice box, sits above trachea
TRACHEA - airway pipe, rings of cartilage support airways from collapsing when pressure is low during inspiration
BRONCHI - trachea splits into two of these into lungs
BRONCHIOLES - bronchi branch into smaller tubes
ALVEOLI - main site of gas exchange, large SA
PLEURAL MEMBRANES - with pleural CAVITY within reducing friction between lungs and inside thorax during ventilation
RIBS - protection, moved by intercostal muscles
EXTERNAL and INTERNAL INTERCOSTAL MUSCLES - contraction ribs pulled up and out, increasing volume of thorax
DIAPHRAGM - dome shaped, relaxes and contracts altering thorax volume
Human ventilation system; starting from external intercostal muscles (substance on alveoli)
- humans ventilate their lungs by NEGATIVE PRESSURE breathing
- when the EXTERNAL INTERCOSTAL muscles CONTRACT they RAISE the ribcage
- OUTER pleural membrane is PULLED OUT this REDUCE PRESSURE in the pleural CAVITY and the INNER pleural membrane moves OUTWARD
- this pulls on the SURFACE of the LUNGS and causes the ALVEOLI to EXPAND - alveolar PRESSURE DECREASES to below atmospheric pressure and air is drawn INTO the lungs
- SURFACTANT in the alveoli reduces SURFACE TENSION and PREVENTS the alveoli COLLAPSING during exhalation
What is and why do insects have a cuticle?
insects have an IMPERMEABLE CUTICLE, outer layer of exoskeleton to which muscle are attached to - REDUCES WATER LOSS by EVAPORATION
