gaseous Exchange Flashcards
How does SA to Volume ratio affect transport molecules?
The lower the SA:Volume ratio, the further the distance molecules must travel to reach all parts of the organism. Diffusion alone is not sufficient in organisms with small SA:Volume ratios.
Why do larger organisms require mass transport and specialised gas exchange surfaces?
Small SA:Volume ratio.
Diffusion insufficient to provide all cells with the required oxygen and to remove all CO2.
Large organisms more active than smaller organisms.
4 features of an efficient gas exchange surfaces
- moist
- Large SA
- Short diffusion pathway
- conc gradient
Describe the gas exchange mechanism in the Amoeba
- unicellular organisms & large SA:Volume ratio
-Thin cell membrane provides short diffusion distance - Simple diffusion across the cell surface membrane is sufficient to meet the demands of respiratory processes
Describe the gas exchange mechanism in flatworms
- multicellular organisms with a relatively small SA:Volume ratio 9 in comparison to the amoeba)
- However, flat structure provides a large surface area and reduces the diffusion distance
- Simple diffusion is sufficient to meet the demands of respiratory processes
Describe the gas exchange mechanism in earthworms
-Cylindrical, multicellular organisms with a relatively small SA:Volume ratio (in comparison to the flatworm)
- Slow moving and low metabolic rates therefore, require little oxygen
- rely on external surface for gas exchange
- circulatory system transports oxygen to the tissues and removes carbon dioxide, maintaining a steep diffusion gradient.
Define ventilation
The movement of fresh air into a space and stale air out of a space to maintain a steep concentration gradient oxygen and carbon dioxide.
Name the organ of gaseous exchange in fish
gills
what are gill filaments
- main site of gaseous exchange in fish, over which water flows.
- they overlap to gain resistance to water flow - slows down water flow to maximise gaseous exchange.
- found in large stacks, known as gill plates, and have gill lamellae which provide a large SA and good blood supply for exchange.
Explain the process of ventilation in bony fish
- Buccal cavity volume increases and pressure decreases to enable water to flow in.
- contraction of the buccal cavity forces water across the gills
- pressure in the gill cavity rises, opening the operculum water leaves.
How is a steep diffusion gradient maintained across the entire gas exchange surface in bony fish.
due to counter current flow
define counter current flow
blood and water flow in opposite directions across the gill plate. maintaing a conc gradient
How does counter current flow maintain a steep diffusion gradient? what is the advantage of this?
- water is always next to blood of a lower oxygen conc - oxygen diffuses into blood from water.
- keeps rate of diffusion constant and enables 80% of available oxygen to be absorbed.
what flow is in a cartilaginous fish
parallel flow
define parallel flow
water and blood flow in the same direction
name and describe the main features of an insects gas transport system
- Spiracles - small, external openings along the thorax and abdomen through which air enters, and air and water leave the gas exchange system
- Tracheae - large tubes extending through all body tissues, supported by rings of chitin to prevent collapse
- Tracheoles - smaller branches dividing off the tracheae
what is the main site of gas exchange in insects
tracheoles
Describe the adaptations of the insect tracheal system to a terrestrial environment.
*Spiracles can be opened or closed to regulate diffusion
* Bodily contractions speed up the movement of air through the spiracles
* Highly branched tracheoles provide a large surface area
* Impermeable cuticle reduces water loss by evaporation
