Section 3-Exchange Flashcards
Do smaller or larger organisms have a large surface area to volume ration?
Smaller organisms
Why can the body surface act as an exchange surface in small organisms?
- Distances are short (less than 0.5mm)
- Surface area to volume ratio is large
Why can large organisms not rely upon their body surface for exchange?
- Distances are too great
- Relative surface area to volume is insufficient
What are the features of a specialised exchange surface?
- Large surface area
- Thin barrier to reduce diffusion distance
- Large concentration gradient
- Selectively permeable surface
What are the features of a specialised exchange surface?
- Large surface area
- Thin barrier to reduce diffusion distance
- Large concentration gradient
- Selectively permeable surface
What would the surface area to volume ratio of a cube that has side 10mm long be?
0.6
What are 3 factors that affect the rate of diffusion of substances into cells?
Surface area
Thickness of membrane
Permeability of membrane
Concentration gradient
Temperature
What is the heat exchange like in small organisms?
Heat is lost more easily - the relative surface area is large
Smaller organisms need high metabolic rate to generate enough heat
What is the heat exchange like in compact shaped organisms?
- Heat loss is minimised
* Small surface area relative to their volume
What is the exchange system called in insects?
The tracheal system
Where does air enter in insects?
-Through spiracles
Can be opened and closed- helps to reduce water loss.
What is the gas exchange structure in insects?
- Spiracle
- Trachea
- Tracheoles
- Muscle
How does an organisms surface area to volume ratio relate to their metabolic rate?
The smaller the surface area to volume ratio, the higher the metabolic rate.
How might a large organism adapt to compensate for its small surface area to volume ratio?
- Changes that increase surface area (e.g. folding)
- Body parts become larger (e.g. elephant’s ears)
- Elongating shape
- Developing a specialised gas exchange surface
Why can’t insects use their bodies as an exchange surface?
They have a waterproof chitin exoskeleton and a small surface area to volume ratio in order to conserve water.
What is the process by which carbon dioxide is removed from a single-celled organism?
Diffusion over the body surface
Why is there a conflict in terrestrial insects between gas exchange and conserving water?
Gas exchange requires thin permeable surface.
Conserving water requires thick waterproof surfaces.
Why does the tracheal system limit the size of insects?
It relies on diffusion to bring oxygen to respiring tissues.
If insects were large, would take too long for oxygen to reach tissues
Name and describe the 3 main features of an insect’s gas transport system.
Spiracles: holes in body surface, can open and close. For gas and water exchange.
Trachea: large tubes extending through all body tissues, supported by rings to prevent collapse.
Tracheoles: smaller branches dividing off the trachea.
What is the process of gas exchange in insects?
- Gases move in and out of trachea through spiracles
- Diffusion gradient allows oxygen to diffuse into body tissue while waste CO2 diffuses out
- Contraction of muscles in trachea allows mass movement of air in and out
Why can’t fish use their bodies as an exchange surface?
Have a waterproof, impermeable outer membrane and a small surface to volume ratio.
What are the gills made up of and what are they covered with?
Gill filaments
Covered with folds called lamellae
How are the lamellae specialised?
Short diffusion distance between water & blood (5um)
Increased surface area at right angles to gill filaments
Counter-current exchange system