The cell membrane Encloses the contents of a cell

All of the above

Allows material to enter and leave the cells

Is selectively permeable

How does a gymnosperm prevent itself from pollinating the same tree

The distant ancestors of tigers may have had bodies without stripes. use the theory of natural selection to explain how tigers may have evolved to have stripes.

Suppose you are provided with an actively dividing culture of e. coli bacteria to which radioactive thymine has been added. what would happen if a cell replicates once in the presence of this radioactive base?