Principles of exchange and transport Flashcards
What do organisms need to exchange substances with their environment.
- Cells require oxygen (for aerobic respiration) and nutrients.
- They also need to excrete waste products like CO2 and urea.
- Most organisms need to maintain the same temperature.
Which has a larger SA:V ratio, a mouse or a hippo?
A mouse.
How do single-celled organisms exchange with the environment?
They use simple diffusion across the cell-surface membrane.
What is the relationship between SA:V and rate of heat loss?
If an organism has a large SA:V then heat is lost more easily.
In multicellular organisms, diffusion across the outer membrane is too slow, why is this?
- Some cells are deep within the body and there is a big distance between them and the environment.
- Large SA:V ratios as it is difficult to exchange enough substances to supply a large volume through a small surface area.
What is the relationship between metabolic demand and size of organisms?
Smaller organisms require a higher metabolic rate, in order to generate enough heat to stay warm.
Given that diffusion in multicellular organisms is too slow to exchange through diffusion only, how do multicellular organisms get the things they need?
Through specialised exchange organs.
Why is the diffusion rate of single-celled organisms quick?
Due to the small distances the substances have to travel.
What is the relationship between animal compactness and heat loss?
A compact animal will have a small surface area relative to volume and therefore will have minimal heat loss.
What is the relationship between animal size and SA:V ratio?
The smaller the animal, the higher the SA:V ratio.
The body temperature of an arctic fox is 37C, the average environmental temperature is 0C. Explain how the arctic fox deals with this:
It is compact so that heat loss is minimised:
- Small ears.
- Round head.
Most gas exchanges have two features which increase SA, what are these?
1) Large SA.
2) Thin.
