In order for multicellular organisms to develop properly and maintain homeostasis, the cells must be able to communicate with each other so that their responses are appropriate and coordinated. Chemical signals released by a cell carry information to cells nearby or far away about how to respond. One example of a chemical signal is a hormone called ghrelin, which was discovered in 1999. Previous research suggests that ghrelin may be involved in development of the pancreas, an organ essential for maintaining blood sugar levels and for aiding digestion of food in the small intestine. Organisms cannot live without a pancreas, therefore, understanding how this organ develops and functions is important for treating medical conditions that arise. To learn more, a team of researchers asked “Is ghrelin necessary for proper formation of the pancreas? If so, how?” They hypothesized that organisms lacking the hormone ghrelin would be missing the proper number and types of cells necessary for pancreatic function. To test this hypothesis, the researchers created mice that lacked ghrelin and compared them to normal mice that contained ghrelin. They removed the pancreas from four mice in each group at three different times (13.5 days, 15.5 days, and 18.5 days) during fetal development. (A total of 12 mice lacking ghrelin and 12 normal mice.) Each pancreas was treated so the researchers could count the number of different types of cells and the quantity of each type. Since the entire pancreas could not be seen at one time, the scientists counted cells using 10 slices out of 100 slices.

1) What are the dependent, independent, and controlled variables?

2) Identify the control group, the number of replicates and the sample size.