Why must arctic fish produce 'anti-freeze chemicals' to survive in icy waters?

What are the formed elements (cell or parts of cell) in blood and what are their functions ?

Use the phylogenetic tree to the right to determine which statement below is true. organisms a and f are not related. organism e is more closely related to organism b than organism f. organisms c and d are more closely related than organisms a and b. phylogenetic trees

Some substances but not other can cross the (blank) membrane of a cell