Diffusion

[killian07]

For EACH of the three taxa groups shown below, describe one system that relies on diffusion for some
aspect of its function (for a total of three different systems). Be sure to a) define how the process of
diffusion works, b) describe the system in each group of organisms that relies on diffusion, and
specifically how diffusion is utilized, c) describe what molecules are involved in the diffusion, and
finally d) describe what the implications would be for all three example groups if diffusion were
impaired (but not completely blocked) in that system.
Groups: angiosperms, fish, humans.

[killian07]

Basically I am thinking that for humans I can say that the diffusion of gases occurs at the capillaries of the lungs and in the tissues of the body. Gases are exchanged. Oxygen enters the the tissues and carbon dioxide enters the lungs to be expelled. The movement of CO2 AND O2 across moiste respiratory surfaces takes place entirely by diffusion. A gas always diffuses from an area of high partial pressure to an area of lower partial pressure. Am I on the right track or does that seem too vague?

For fish I would say that they pumo water throught their mouth and over the gill arches using coordinated movements of the jaw and operculum (gill covers) for the ventilation. Each gill arch has two rows of gill filaments composed of flattened plates called lamallae. Blood flowing through the capillaries within the lamallae picks up O2 from the water by diffusion. There is a counter current flow of water and blood that maintains a partial pressure gradient down which 02 diffuses from water into the blood.

For Angiosperms....This one was tough for me...I think that I should be talking about Angiosperms dependency on their ability to balance water uptake and loss. The net loss or uptake of a water molecule occurs by osmosis, the diffusion of water across a membrane. This is passive transport requiring no energy. Gradients of water potential drive the osmotic movement of water from cell to cell within root and leaf tissue.

Does that all sound correct? If you have anything to add I would appreciate all of the help:)

[JackBean]

describe one system that relies on diffusion for some
aspect of its function (for a total of three different systems)

I think you described one system for human and fish (although with different media)