Distinguish the form and nature of chromosomes between dividing and non dividing cells

The form and nature of chromosomes varies during the life cycle of the cell and they differ between dividing and non dividing cells. 
Non-dividing cells are in the Interphase when the most of the chromatin (complex of DNA and proteins that forms chromosomes) is decondensed and throughout the nucleus. In that form it is called Euchromatin.
In dividing cells it is called Heterochromatin when the most of the chromatin is condensed and chromosomes are noticeable.

The open ocean begins at the low-tide mark and extends to the end of the continental shelf

above statement is not a true statement about the open ocean because the open ocean has low levels of nutrients. most of the photosynthetic activity on earth occurs in the open ocean within the photic zone. organisms in the deep ocean are exposed to frigid temperatures and total darkness but it does not begin at the low-tide mark.