Well, I'm assuming you're talking about these terms...
Species, Genus, Family, Order, Class, Phylum, Kingdom, Domain
A good way to remember this is;
Does King Philip Come Over For Great Spaghetti
(However, this is in order from most specific to least specific)
Answer:
Pioneer species/organisms help modify the environment because they are the first organism to live on that "terrain" or environment and they open up the chance to make more organism, also when they die and decompose they make more soil so that more organisms can grow.
Explanation:
Index fossils (also known as guide
fossils, indicator fossils or zone
fossils) are fossils used to define
and identify geologic periods (or
faunal stages).
Answer:
Your question was a bit vague... but Crenarchaeota, Euryarchaeota, Korarchaeota, Thaumarchaeota and Nanoarchaeota are the four types of Archaea.
Hope this helps!