An ecologist conducts a greenhouse experiment to study the effect of water concentration added to soil on the productivity of sunflower seedlings. what is the independent variable in this experiment?

The circles, or orbits, for electrons are called energy levels. each level can hold only a certain number of electrons. add electrons to each level until you can't add any more. how many electrons can each level hold?

Identify the composition of oceanic and continental crystal rocks.in a model of earth’s interior,where would these rocks appear?

Anurse is caring for a 42-year-old client who is scheduled for an amniocentesis during the fifteenth week of gestation because of concerns regarding down syndrome. what other fetal problem does an examination of the amniotic fluid reveal at this time?