Adaptations For Gas Exchange Flashcards
(44 cards)
Definition of gas exchange
The diffusion of gases down a concentration gradient across a respiratory surface, between an organism and its environment.
Definition of respiratory surface
The site of gas exchange
Features of a respiratory surface
- large enough surface area , relative to volume of organism
- thin- diffusion pathway is short
- permeable- gases diffuse easily
- have a mechanism to produce a steep concentration gradient i.e. Bring in oxygen or removing co2 rapidly
Features of unicellular organism e.g. Amoeba ( single celled organisms)
- large SA: volume
- cell membrane is thin- diffusion into the cell is rapid
- thin- diffusion distances inside cell are short
What do unicellular organisms’ features allow them to do?
- absorb enough oxygen to meet respiration needs
- remove co2 fast enough to prevent high concentration build up and making cytoplasm to acidic for enzymes to work.
Why is the problem with larger organisms and gas exchange?
Lower SA: volume than smaller organisms
How are flatworms adapted for gas exchange?
Being flat they have a much larger surface area
No part of body is far from the surface- short diffusion pathway
How is an earthworm adapted for gas exchange?
- cylindrical- larger SA: volume than compact organism of same volume
- skin is respiratory surface, secretes mucus to keep moist, restricted to damp environment of soil
- low oxygen requirement- slow moving
- haemoglobin in blood, o2 round body, carries o2 away from surface- maintains gradient
Features of multicellular organisms:
- higher metabolic rate( more o2 needed)
- tissues and organism become more interdependent ( increase in size+ specialisation of cells)
- Ventilation mechanism- maintain steep concentration gradient
- respiratory must be thin. Inside your organism so the are protected
Problems for terrestrial organisms with gas exchange
- water evaporates from body surfaces- dehydration
- water molecules pass through gas exchange surfaces easily so are always moist- lose a lot of water
How are amphibians adapted for gas exchange?
Skin is moist and permeable
Well developed capillary network just below surface
Gas exchange through skin and lungs when animal is active
How are reptiles adapted for gas exchange?
Lungs have a complex internal structure, increasing SA for gas exchange
How are birds adapted for gas exchange?
Lungs process large amounts of oxygen- flight requires a lot of energy
Don’t have a diaphragm
Ribs and flight muscles ventilate lungs
How are folks adapted for gas exchange?
- one way current of water
- many folds- large SA
- large SA- maintained by density of water flowing through
Where are the gills in cartilaginous fish?
- gills in gill pouches
- 5 spaces in each side
- open at gill slits
Why is the gas exchange system less efficient in cartilaginous fish?
- water is not forced over gills- must keep swimming for ventilation
- parallel flow
Definition of parallel flow
Blood and water flow in the same direction at the gill lamellae, maintaining the concentration gradient for oxygen to diffuse into the blood only up to the point where concentrations are equal
- bloods oxygen conc is limited to 50%
- does not occur across whole gill lamellae
Describe the structure of bony fish
- internal skeleton made of bone
- gills are covered with operculum
How does ventilation maintain flow in bony fish?
- water is forced over gill filaments by pressure differences
Water potential in mouth is higher than in opercular cavity
How do bony fish take in water?
1 mouth opens
2 operculum closes
3 floor of the mouth is lowered
4 volume inside mouth cavity increases
5 pressure inside mouth cavity decreases
6 water flows in- external pressure higher than pressure inside mouth
How is water forced out over the gills in bony fish?
1 mouth closes 2 operculum opens 3 floor of mouth is raised 4 volume inside mouth cavity decreases 5 pressure inside mouth cavity increases 6 water flows out over the gills- pressure in mouth cavity higher than in opercular cavity and outside
Describe the gills in bony fish
- 4 pairs of gills
- each supported by gill arch made of bone
- Gill filaments- thin projections along each gill arch
What are gill lamellae?
Gas exchange surfaces on the gill filaments
Held apart by water flowing between them- provide a large SA for gas exchange
Out of water they stick together and collapse- less area is exposed and not enough gas exchange takes place
What is counter current flow?
Blood and water flow in opposite directions at the gill lamellae, maintaining the concentration gradient and therefore oxygen diffusion into the blood, along their entire length
