Choose the two (2) compounds that are called purines:

Which chromosomal effect is demonstrated in the following illustration?  Deletion.jpg

The steps, or rungs, of the DNA ladder-like structure consist of complementary chemicals that are:

List one principle of sustainability.

Any set of components that interacts in a regular way describes a ___________________.      

Herbivores are primary consumers.

The _____________ method is used by ecologists and biologists to learn more about the natural world.

Secondary succession occurs when an area has a soil layer already established.

The following is one of the components of the earths life support system:

__________________ are types of cells that are enclosed by a membrane but have no distinct membrane bound nucleus.