Option 1 is the correct answer
True, our ecosystem is not independent. Everything depends on everything else to survive. :)
Differentiation occurs numerous times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types.
Index fossils (also known as guide
fossils, indicator fossils or zone
fossils) are fossils used to define
and identify geologic periods (or
faunal stages).
