The two strands of a DNA double helix are held together by:

A. ionic bonds.

B. hydrogen bonds.

C. nonpolar covalent bonds.

D. polar covalent bonds.

E. hydrophobic exclusions.

Just a few years ago, biologist and medical personnel were surprised to learn that fetal cells can escape and enter the mother's blood. How can these cells be used in fetal testing?

What is kudzu classified as?

Why do vertebrate embryos show similarities between organisms that do not appear in the adults?

Where does the heat that warms your body come from?

Is it possible to have a molecule that is also an element? If so, give an example.

Cartilage is part of the skeletal system. True False

Which is made up of organic molecules? copper electrical wires plastic storage containers table salt antacid

How does nitrogen leave a food chain? A. Primary consumers eat nitrogen-containing green plants. B. Producers absorb nitrogen-containing nutrients by their roots. C. Decomposers break down nitrogen-containing waste material from primary consumers. D.

Diffusion is important for living organisms because ...

What does dichotomous means when classifying objects or organisms?