A gazelle has learned that lions represent danger. On seeing a lion, the gazelle's heart rate increases and the gazelle runs from the lion. What levels of organization are required for this response to occur?

Which of the following statements is not true? • a. covalent compounds have low melting and boiling points. • ob. covalent bonds between atoms of a compound are relatively weak compared to bonds between molecules. • c. covalent bonds occur between nonmetals. • d. covalent compounds are often gases or liquids.

Determine the wavelength of the light absorbed when an electron in a hydrogen atom makes a transition from an orbital in the n=3 level to an orbital in the n=7 level.

Which fact represents evidence for the big bang theory?