2.2 - adaptations for gas exchange Flashcards
give 2 examples of a respiratory surface in which gas exchange happens efficiently.
- gills of a fish
- alveoli in lungs of a mammal
what 4 features must an exchange surface have for it to be rapid diffusion?
- large SA to volume
- thin
- permeable
- have a mechanism to produce steep gradient across respiratory surface by bringing oxygen or removing co2
what is meant by a unicellular organism?
single-celled organism
single-celled organisms is very thin and has a large SA therefore they can do 2 things…?
- absorb enough oxygen to meet their needs
- remove co2 fast enough so it doesn’t build up a concentration which wold make the cytoplasm too acidic for enzymes to function
why are multicellular animals not efficient at gas exchange?
lower surface area to volume ratio - diffusion across surfaces is not efficient enough
name 3 features of a earthworm.
-low oxygen requirement - slow moving
-cylindrical shape so SA to volume ratio is smaller than flat
worms
-haemoglobin present in blood - carries oxygen around body in blood vessels
what 2 features do multicellular animals have that unicellular organisms don’t?
- higher metabolic rate
- more specialised cells, tissues and organs - therefore more interdependent
life on earth involved in water so what major problems may this have on terrestrial animals (entirely on land)?
-water evaporates from body surfaces - dehydration
where does gas exchange take place on a amphibian?
through the skin - moist, permeable and well developed capillary network
how do reptiles have an increased surface area for gas exchange?
lungs have a more complex internal structure
why do birds process large volumes of oxygen?
flight requires lots of oxygen
how do birds ventilate their lungs more efficiently compared to vertebrates?
do not have a diaphragm but their ribs and flight muscles help
what 2 features do gills have?
- one way current of water
- folds - provide large SA over which water can flow
what are the two types of fish - why are the different?
cartilaginous fish - skeleton of cartilage
bony fish- skeleton of bones
give an example of a cartilaginous fish and describe their gills
shark - 5 gills on each side
what are 2 reasons why cartilaginous fish’s ventilation system is less efficient than the bony fish?
- do not have special mechanism to force water out of gills
- blood travels same direction as water through the gill - PARALLEL FLOW - means only 50% of oxygen can diffuse
on a bony fish the gills are covered by what? what do the mean?
operculum- doesn’t open directly
what does ventilation allow?
maintains a continuous, unidirectional flow so water is forced over the gill filaments
in ventilation what is the mechanism that operates to take water in? 6 steps.
- mouth opens
- operculum closes
- floor of mouth is lowered
- volume inside of mouth cavity increases
- pressure inside mouth cavity decreases
- water flows in AS external pressure is higher tan the pressure inside mouth
in ventilation what is the mechanism that operates to force water out by the gills? 6 steps.
- mouth closes
- operculum closes
- floor of mouth raised
- volume inside the mouth cavity decreases
- pressure inside mouth cavity increases
- water flows out over gills AS pressure in mouth is higher than opercular
explain in terms of gills why fish die if they are out of water for more than a very short time.
gill plats are held apart by water flowing between them so out of water they stick together and gills collapse - less area exposed - not enough gas exchange can take place
describe what is meant by counter-current flow.
blood and water flow In opposite directions at the gill lamellae - maintains concentration gradient
what 3 things do gills provide for carbon dioxide exchange?
- a specialised respiratory surface
- a large surface extended by gill filaments and gill lamellae
- extensive network of blood capillaries
what is the air tight compartment the lungs are in?
the thorax
what lines the thorax and covers each lung?
plural membranes - fluids prevents fiction
what is at the bottom of the thorax?
dome-shaped sheet of muscle called the diaphragm
the ribs surround the?
thorax
what is the trachea?
a flexible airway - brings air to lungs
what are the two bronchi?
branches of the trachea
what arise from the bronchi?
bronchioles
at the end of the bronchioles are air sacs called…?
alveoli
for air to enter the lungs, the pressure inside the lungs must be below..?
atmospheric pressure
what 6 things happen during inspiration? (breathing in)
- external intercostal muscles contract
- ribs are pulled upwards and outwards
- diaphragm muscles contact so it flattens
- thorax volume increases
- reduced pressure in lungs
- atmospheric pressure is greater than pressure in lungs so air is forced into lungs
what 6 things happen during expiration? (breathing out)
- external intercostal muscles relax
- ribs move downwards and inwards
- diaphragm muscles elax so it comes up
- thorax volume decreases
- increased pressure in lungs
- air pressure in lungs is greater than atmospheric pressure so air is forced out
what are 4 reasons why the alveolus is efficient at gas exchange?
- provide large SA relative to volume of body
- aveoli have walls made of squamous epithelium - only one cell thick - short diffusion pathway
- capillary walls are only one cell thick
- extensive capillary network - maintains diffusion gradient
why is there less oxygen in the expired air than the inspired air?
oxygen is absorbed into bloat the alveoli and used in aerobic respiration
why is there more carbon dioxide in the expired air than the inspired air?
diffuses from the plasma into the alveoli
why is there the same amount of nitrogen in the expired and inspired air?
nitrogen neither absorbed nor used
in plants in respiration what happens to oxygen and co2?
oxgen is taken in day and night
co2 is out day and night
in plants in photosynthesis what happens to oxygen and co2?
oxygen out in the day
co2 in, in the day
NONE in the night - plant do not photosynthesise
why, in plants is the overall gas produced oxygen?
during day rate of photosynthesis is faster than rate of respiration - so more oxygen produced in photosynthesis than used in respiration
describe how gases diffuse through the stomata in a leaf?
down a concentration gradient, gases in sub-stomatal air chambers diffuse through intercellular spaces between spongy mesophyll cells, into cells
what does a large surface area have significance for gas exchange?
room for many stomata
what do air spaces in spongy mesophyll have significance for gas exchange?
allow oxygen and co2 to diffuse between stomata and cells
what do stomatal pores have significance for gas exchange?
gas exchange in and out of leaf
what does a large surface area have significance for photosynthesis?
capture as much light as possible
why does a thin leaf have significance for photosynthesis?
light penetrates through leaf
why do palisade cells being elongated have significance for photosynthesis?
can accommodate a large number
why do palisade cells packed with chloroplasts have significance for photosynthesis?
capture as much light as possible
define stomata.
pore on lower leaf surface bounded by two guard cells through which gases and water vapour diffuse
if waters enter the guard cells the stomata becomes…?
turgid and swelled and the pore opens
if water leaves the guard cells the stomata becomes…?
flaccid and pore closes
what 3 processes happens when the pore opens?
- chloroplasts in guard cells photosynthesise producing ATP
- stored starch converted to malate
- malate ions lower water potential - water enters by osmosis
what is transpiration?
when plants lose water through evaporation which causes plant to wilt
what 3 situations does the stomata close to balance the conflicting needs of gas exchange and control of water loss?
- at night - insufficient light for photosynthesis
- very bright light - usually accompanied by intense heat - increase evaporation
- excessive water loss
