Adaptations For Gas Exchange Flashcards
What is a respiratory surface?
The site of gas exchange
Examples of respiratory surfaces:
Gills of a fish
Lungs of a mammal
Tracheae of an insect
Essential features for respiratory surfaces?
Large surface area (increases area for movement of gases)
Thin membrane ((short diffusion pathway)
Permeable membrane (to allow gases through)
Moist (so gases will dissolve and diffuse faster)
Concentration gradient across a membrane
How is amoeba suited for gas exchange?
Habitat = water (moist)
Thin, permeable membrane
Oxygen will diffuse across the entire body surface (large surface area)
Has concentration gradient (what oxygen it gets, it uses)
The problem with multicellular organisms?
There has to be a limit to cell size and a point will be reached where the length of the diffusion pathway limits the efficiency of the process of diffusion.
The organism can get larger if the cells aggravate together to become multicellular
However the larger the organism the smaller the surface area to volume ratio
Why flatworm is good at gas exchange?
Habitat = water (moist)
Flattening itself has elongated the body (large surface area)
Why earthworms are good at gas exchange?
Long (large surface area)
Blood vessels carry oxygen around the body
Secretes mucus onto surface (moisture)
Habitat - terrestrial but DAMP ENVIRONMENT
low metabolic rate (rate of energy expenditure by body)
Respiratory pigment within blood
Where are the spiracles on an insect?
On the thoracic and abdominal body segments of an insect
What are spiracles?
Basically pores in the exoskeleton of the insect
What are exoskeletons and why do insects need them?
Insects have this covering (exoskeleton) to prevent them from drying out (heat) but by having the waterproof layer, they are impermeable to gases.
What do spiracles possess. And what are they lined with?
They possess valves which are responsible for opening and closing spiracles.
They are lined with hairs which reduce water loss.
Process of gas exchange when insects are at rest?
They close the spiracles to reduce water loss which helps maintain a concentration gradient.
Oxygen is reduced of cellular respiration in body, decreasing the levels of oxygen, creating a concentration gradient.
An active insect can ventilate the system through muscular movements of the abdomen. This is done by the alternate compression and expansion of the tracheal.
If it begins resourcing anaerobically, so can’t ventilate quick enough, lactic acid is produced. By increasing the amount of lactic acid in the muscle, it is lower than the water potential in the fluid at end of tracheoles. This allows osmosis to occur between the high water potential in the tracheoles and respiring tissue, clearing the tracheoles of fluid and allowing more room for oxygen.
Amount of gases inspired and expired!
Oxygen
Inspired - 20%
Expired - 16%
Carbon dioxide
Inspired - 0.04%
Expired - 4%
Nitrogen
Inspired - 79%
Expired - 79%
Water vapour
Inspired - variable
Expired - saturated
Amount of oxygen absorbed in mammals and fish?
Mammals 20%
Fish 80%
What are the problems that under water organisms face?
Water contains around 25x less oxygen than air
Rate of diffusion of oxygen is a lot slower in water
Water is more dense than air, so it doesn’t flow easily as it is more difficult to ventilate the respiratory surfaces
Why do fish need gills?
They are very active, so require a specialist respiratory system
They have a large SA for gas exchange, created by the many folds
A specialised pumping mechanism ensures a one way current of water flows constantly over the gills
An extensive capillary network maintains diffusion gradients at the Gill surface (and fish have haemoglobin to carry oxygen)
Why do fish use the counter current?
Once equilibrium is reached, there is no net movement of oxygen into the blood, therefore, with a parallel flow blood will only be up to 60-70% saturated with oxygen
The counter current flow results in the oxygen concentration gradient between the blood in the gills and the water being maintained across the entire length of the Gill lamella
The flow of ventilating gills : (11)
- Mouth opens
The buccal cavity floor is lowered
This increases the volume and decreases the pressure of the buccal cavity compared to outside
Water rushes into the mouth down a pressure gradient
Operculum cavity expands
The buccal cavity floor is raised
The pressure inside the buccal cavity is now higher than in the operculum cavity
Water moves from the buccal cavity, over the gills, into the operculum cavity
The mouth is now closed and the operculum opens
The sides of the operculum cavity move inwards, increasing the pressure
Water rushes out of the fish through the operculum
Rate of diffusion equation:
Thickness of membrane
Process when humans inspire?
External intercostal muscles contract
Ribs are pulled upwards and outwards
The diaphragm muscles contract, so it flattens
Outer pleural membrane is pulled out
thorax volume increases
Reduces pressure in the lungs
Inner pleural membrane pulled outwards. This causes ‘pull on the lungs and the alveoli will expand
Atmospheric air pressure is now greater than pressure in the lungs, so air is forces into the lungs
Process when humans expire?
External intercostal muscles relax
Ribs move downwards and inwards
At the same time, the diaphragm muscles relax so it domes upwards
Outer pleural membrane pulled in
Both actions decrease the thorax volume
This increases pressure in the lungs
Inner pleural membrane pulled inwards
Air pressure in lungs is now greater than atmospheric pressure so air is forced out of the lungs
Role of surfactant?
A chemical which coats the inside layer of the alveoli
Job is to reduce surface tension and stop the alveoli from collapsing
Role of guard cells and stomata in the day:
The guard cells possess chloroplasts so photosynthesis will take pace and ATP will be synthesised
The ATP provides energy for the active transport of K+ ions into the guard cells
Starch sitting the guard cells is converted to malate
The presence of both Malate and k+ ions will lower the water potential in the guard cells. Water will enter the guard cell by osmosis
Due to differences in the thickness of the cell wall (outside thinner than inside) the presence of the water will cause the thinner wall to stretch (more than the inner walls) so a pore appears between the two guard cells
Stoma opens
