Okay so firstly we should look at why we have mass transport. Luckily for us I already covered it here: 3.3.1
Basically what i'm saying is that many cells in multicellular organisms are too far from exchange surfaces to exchange materials by diffusion/active transport alone. To solve this problem, cells of multicellular organisms bathe in tissue fluid (tissue fluid is the environment around the cells). When absorbed, materials are distributed throughout the tissue fluid so cells can absorb them. Example materials include nutrients (e.g fatty acids, amino acids, glucose, minerals, vitamins), gases (respirator gases, oxygen and carbon dioxide), heat, and urea (and other excretory products). Diffusion is enough to transport materials over short distances but the efficient supply of materials over a large(r) distance requires a mass transport system.
This is because with increasing size the surface area to volume ratio decreases (read this). Eventually the surface area to volume ratio decreases so much that diffusion/active transport alone can no longer support the organism. A transport system is required to take materials to/from the specialised exchange surfaces. Materials must be transported between exchange surfaces/external environment/internal environment/cells etc etc. As organisms get bigger the issues and organs they have have become more developed and specialised and also more dependant on each other making a transport system essential.
Transport systems should have certain features to be 'good'. These include:
Ta dah.
Basically what i'm saying is that many cells in multicellular organisms are too far from exchange surfaces to exchange materials by diffusion/active transport alone. To solve this problem, cells of multicellular organisms bathe in tissue fluid (tissue fluid is the environment around the cells). When absorbed, materials are distributed throughout the tissue fluid so cells can absorb them. Example materials include nutrients (e.g fatty acids, amino acids, glucose, minerals, vitamins), gases (respirator gases, oxygen and carbon dioxide), heat, and urea (and other excretory products). Diffusion is enough to transport materials over short distances but the efficient supply of materials over a large(r) distance requires a mass transport system.
This is because with increasing size the surface area to volume ratio decreases (read this). Eventually the surface area to volume ratio decreases so much that diffusion/active transport alone can no longer support the organism. A transport system is required to take materials to/from the specialised exchange surfaces. Materials must be transported between exchange surfaces/external environment/internal environment/cells etc etc. As organisms get bigger the issues and organs they have have become more developed and specialised and also more dependant on each other making a transport system essential.
Transport systems should have certain features to be 'good'. These include:
- A suitable medium to carry materials (e.g we have blood) - usually liquid based as most substances can dissolve in water and can be moved around easily. We also have air for gas exchange
- Form of mass transport in which the medium is moved around (e.g ventilation/movement of blood)
- Closed system of vessels containing the transport medium to transport the transport medium to all of the organism
- A mechanism for moving the transport medium - a pressure gradient (e.g our heart creates a pressure gradient that moves the blood around, contraction of muscles in the tracheae moves air in an insect, evaporation of water (plants).
Ta dah.
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