Which statement best describes a keystone species? a. it has little genetic variation. b. it has an extremely high population. c. it remains unaffected by all environmental changes. d. it has a strong influence on the ecosystem. e. it’s the first species to populate a new ecosystem.

Which type of bacterial reproduction is depicted in the diagram?

Match the following terms describing electrical events with the correct phases of the cardiac cycle. the ventricular muscle cells depolarize at the start of this phase. during this phase, na+ entry through the funny channels causes the pacemaker potential of sa nodal cells to gradually become less negative until it reaches threshold. the ventricular muscle cells repolarize right before this phase. the cytosolic concentration of calcium in the contractile cells of the ventricle is highest during this phase. a. isovolumetric relaxation b. ventricular ejection c. isovolumetric contraction d. ventricular filling

An easy way to calculate the amount of energy available at each level is to what?