I taught some gardening classes a few years back and this chart really helps you see what the different types of seeds are. Seeds are one of the main ways we keep eating.
Commercial growing does not allow for the diversity that might be needed for the future. We all know about the potato famine in mid 1800 Ireland. The reason for that horrible event was lack of diversity in the type of potatoes they grew. If you have three types of squash and you grow them and one can't take a cold spring you still have the other two types. Lets say a beetle likes on of the types of squash and you only get just a few eatable squash from that plant. BUT the last plant is hearty and makes it through. You will then have squash to eat and store seed from. My little example is no where near good enough to explain plant diversity to you but it's a start.
World wide there are plants that could make a difference in many lives. Many of these plants are no longer being grown with our large farm growing methods. Surprising but if you don't grow a seed every year or so it may not grow. So when an industry as farming goes to hybrid and only uses one kind of plant the other plants will soon disappear if someone doesn't grow the seeds and keep the plant going.
There are groups who collect and save seeds all over the world. Bless them all for their concern and care. There are seeds stored in carefully prepared conditions in hopes of saving this diversity. I heard one was in Iran and is lost. Typhoon Xangsane destroyed another important collection. Sad, many plants we won't have now. A new one in Norway has been set up and it is a dandy. If you want to know more about this you can check....
http://www.seedsavers.org/whatsnew.asp go to the bottom of the page for a nice article on Seed savers efforts for the Norway vault.
You will learn a lot about seeds from my chart above. Ask questions, I can answer them.http://www.croptrust.org/main/arctic.php?itemid=216