Exchange: The Movement Of Gases Flashcards
What is the definition of the term ‘surface area’?
The total area of the organism that is exposed to the external environment.
As the surface area and volume of an organism increases, the surface area to volume ratio decreases. This is because volume increases much more rapidly than surface area as size increases.
What is the surface area of like in small organisms?
Small organisms, i.e amoeba, have a very large surface area in comparison to their volume. This means there is a large SA for exchange of substances, but also there is a smaller distance from the outside of the organism to the middle of it. As a result, organisms can simply exchange substances across their surface.
What is the definition of the term ‘volume’?
The total internal volume of the organism (total amount of space inside the organism)
What is the surface area like in large organisms?
The larger the organism is the smaller its SA:V ratio, the larger the distance from the middle to the outside. Larger organisms will typically have a higher metabolic rate too, which demands efficient transport of waste out of cells and reactants into the cell. As a result, they have adaptations that help make the exchange across surfaces more efficient.
What is a ‘metabolic rate’?
The amount of energy expended by that organism in a time period e.g daily
What is ‘metabolic demand’?
How much oxygen and nutrients an organism needs to take on daily to respire enough to maintain the metabolic rate.
As a general rule, the greater the mass of an organism, the higher that organisms metabolic rate. This is because organisms with high metabolic rates require more efficient delivery of oxygen to cells.
What is the metabolic rate like in smaller organisms?
They have a lower metabolic rate due to a greater SA:V ratio. However, this also means they lose heat more easily and need greater amounts of energy to maintain a constant internal temperature: so, per unit of body mass, small organisms actually have a higher metabolic rate than larger organisms.
