Valence is the number of electrons an atom must gain or lose in order to its outer energy level or have a stable octet in its outer shell.

complete
lose
gain

Dwarf galaxies are select one: a. relatively rare. b. not very bright c. mostly spiral shaped. d. none of these.

1. variations in a population of moths allow for some of its members to be able to adapt to environmental changes. the better adapted of the moths will be able to survive the change and thus prevail as the “fittest” of the species. (a) describe three mechanisms in which variation can occur within a species population. (b) explain which mechanism or mechanisms would be responsible for the survival of a population of peppered moths better than white moths in an environment affected by industrial soot. justify your answer.

How does the nervous system affect the excretory system?