The cardiac electrical impulse normally begins spontaneously in the sa node because
a. of the superior location of the sa node in the right atrium.
b. the sa node is the only area of the heart capable of spontaneous depolarization.
c. of the rich sympathetic innervation of the sa node.
d. this area depolarizes more rapidly than any other portion of the conduction system.
e. of action potentials from the cardioregulatory cente

Which of the following statements is most likely correct about a rock belonging to the jurassic age and a rock belonging to the cambrian age? options: 1) they have identical fossils of organisms that have evolved over time. 2) both have animal fossils preserved in them due to weathering and erosion. 3) they contain different fossils because life on earth has changed through time. 4) the fossils in them were formed on the surface of earth due to exposure to sunlight.

Two students are working together on an experiment that measures the effect of different liquid fertilizers on the thickness of plants’ stems. which is most likely to result in the greatest amount of error in their scientific experiment? a. one student measures the plant stem widths by using calipers. the other student measures the widths of the same plant stems again by using a different pair of calipers. b. one student measures the plant stem widths by using calipers. the other student types the measurements as they are taken into a computer spreadsheet. c. one student weighs liquids for the experiment by using a calibrated scale. the other student weighs liquids for the experiment by using a different calibrated scale.

In meiosis ii during anaphase ii which structures separated homologous chromosomes or sister chromatids