To derive is defined as to come from, be created from or be developed out of something else. An example of derive is when you get the idea for a new fund raising event based on the event the previous year.
Rubidium: geological information. Rubidium is far too reactive to be found as the free metal in nature. It is relatively rare, although it is the 16th most abundant element in the earth's crust. Rubidium is present in some minerals found in North America, South Africa, Russia, and Canada. It is found in some potassium minerals (lepidolites, biotites, feldspar, carnallite), sometimes with caesium as well.
Helicosporidium is a genus of nonphotosynthetic parasitic green algae that is thought to contain a vestigial chloroplast. Genes from a chloroplast and nuclear genes indicating the presence of a chloroplast have been found in Helicosporidium even if nobody's seen the chloroplast itself.