Gaseous Exchange Flashcards
list the materials an organism will exchange with its environment (4)
- respiratory gases
- nutrients
- excretory products
- heat
what features make a good gas exchange surface? (3)
- large surface area
- high concentration gradient
- short diffusion pathway
“for exchange to be efficient, the surface area must be ___________ compared to its volume”
large
what is the difference between the SA:VOL ratio of a smaller organism and the SA:VOL ratio of a larger organism?
smaller organism = larger SA:VOL ratio
larger organism = smaller SA:VOL ratio
state the advantage and the disadvantage of small organisms having a large SA:VOL ratio
advantage
it means having a faster diffusion rate
disadvantage
the animal will lose more heat
what do smaller organisms do to compensate for the extra loss of heat? (3)
- they increase their metabolic activity through processes such as respiration
- a by product of respiration/metabolism is heat
- this allows smaller organisms to maintain body temperature.
more heat loss =
increased metabolic rate
less heat loss=
decreased metabolic rate
state the main disadvantage of large organisms having a small SA:VOL ratio
they will have a slower rate of diffusion
what have larger organisms evolved in order to counter their slower rate of diffusion?
specialised ‘exchange systems,’ such as the lungs and intestines, that do have a large SA:VOL ratio
what is the name of the gas exchange system in insects?
the tracheal system
how does the movement of oxygen into insects occur? (4)
- oxygen enters through the spiracles and into the tracheae
- spiracles close
- oxygen diffuses through the tracheae into the tracheoles where gas exchange occurs
- oxygen is delivered directly to respiring tissues
which exact structure in the insects is the site of gas exchange?
the tracheoles
what are the adaptations of the tracheal system (the tracheoles) for efficient gas exchange? (3)
highly branched, provide a large surface area for faster diffusion
abdominal pumping, maintains the concentration gradient for oxygen and carbon dioxide
walls are one-cell thick, short diffusion distance
what exactly is abdominal pumping? (2)
- movement of the insect’s body by its muscles
- increases pressure and so forces carbon dioxide out
insects must balance minimising water loss with efficient gas exchange
to limit water loss, insects may have: (3)
rigid exoskeleton
covered with a waterproof cuticle
impermeable so reduces water loss
spiracles close
to prevent water loss
small hairs around the spiracles
trap water
reduces the water potential gradient
what is the name of the gas exchange organ in fish?
gills
how does the movement of oxygen into fish occur? (6)
- water carrying oxygen moves in through the mouth
- the gills have finger like projections called gill filaments
- each filament has many lamellae
- lamellae contain capillaries
- most oxygen is removed and enters the capillaries
- water containing little oxygen leaves through the gill opening
which exact structure of the fish is the site of gas exchange?
lamellae
what are the adaptations of the gills for efficient gas exchange? (3)
many gill filaments that contain many lamellae
provide a large surface area for diffusion
countercurrent flow
maintains the diffusion gradient along the entire length of the gill lamellae
lamellae have a thin epithelium
short diffusion distance
what exactly is countercurrent flow?
water with a high oxygen concentration and blood with a low oxygen concentration flow in opposite directions
how does the movement of carbon dioxide into plants occur? (3)
- carbon dioxide enters via the stomata, which are opened by guard cells
- diffuses into the air spaces of the spongy mesophyll down a concentration gradient
- palisade mesophyll cells have a lower conc. of carbon dioxide owing to photosynthesis, so it moves from the air spaces into these cells down a concentration gradient
which exact structure of a plant is the gas exchange organ?
the leaf
what are the adaptations of the leaf for efficient gas exchange? (3)
flat
have a larger SA:VOL ratio
many stomata
allow air to move in and out of the leaf
air spaces in the spongy mesophyll
short diffusion pathway
plants balance minimising water loss with efficient gas exchange
to limit water loss, plants contain three key features:
guard cells close the stomata at night
because less CO2 is required at this time of day
waxy cuticle
most stomata found in the lower epidermis
what are xerophytes?
plants that live in dry/arid environments
what are the adaptation of xerophytes to reduce water loss? (4)
thick waxy cuticles
increased diffusion distance
hairs, stomata in pits, rolled leaves
trap water vapour and decreases water potential gradient
spines
reduces the SA:VOL ratio
small leaves with reduced stomata
reduced transpiration
what have humans evolved in order to carry out efficient gas exchange?
lungs
how do the lungs help with gas exchange?
they provide a larger SA:VOL ratio, which enables a faster rate of diffusion
describe the pathway oxygen takes through the body in order to enter the lungs and blood stream
oral/nasal cavity
trachea
bronchi
bronchioles
alveoli
which exact structure of the lungs is the site of gas exchange?
the alveoli
what are the adaptations of the alveoli for gas exchange? (4)
large surface area
surrounded by a network of capillaries
ensures a large concentration gradient between the oxygen and carbon dioxide
alveolar epithelium is one cell thick
short diffusion distance
alveolar epithelium permeable to oxygen and carbon dioxide
mechanics of breathing: inhalation (4)
- diaphragm contracts; flattens
- external intercostal muscles contract; rib cage up and out
- thoracic cavity: size increases, pressure decreases
- air moves into the lungs down a pressure gradient
mechanics of breathing:exhalation (4)
- diaphragm relaxes; returns to its dome shape
- external intercostal muscles relax, internal intercostal muscles contract; rib cage in and down
- thoracic cavity: size decreases, pressure increases
- air moves out of the lungs down a pressure gradient
how is pulmonary ventilation calculated?
pulmonary ventilation rate = tidal volume x breathing rate
