The answer is; The three main organs that serve as the site for the regulation of blood calcium levels are the bones, the intestines, and the pancreas.
The pancreas is not involved in calcium regulation in the body. Other than bone and small intestines, the other organs significant in this homeostasis of calcium in the blood are the kidneys, thyroid gland, and the brain. When the calcium level is too low, PTH is produced by the parathyroid gland and causes bone resorption, increased uptake of calcium in small intestines and increased re-absorption of the ions in the kidneys. When the calcium level is too high, calcitonin is produced by the thyroid gland and reduces bone resorption/ increases bone calcium absorption., and reduces reabsorption in the kidneys.
Answer:
I and III only
Explanation:
Crop rotation is a farm practice that involves cultivating different species of crops on the same land at different seasons. In other words, the different crops are rotated. Crop rotation is done for various reasons including; improvement of soil fertility, pest and disease control etc.
In this case, a crop rotation of various grains and legumes would be an appropriate solution for the following problems:
- The nutrients in the soil on a farm are being depleted: Legumes are known to be rich in nitrogen and hence add nitrogen to the soil due to the nitrogen-fixing microbes in their roots. Hence, rotating between grains and legumes can help return the depleted nutrients (by grains) to the soil.
- A particular kind of pest is infesting the soil on a farm: Most pests are usually crop-specific, hence, planting only one type of crop can make that soil be infested with a particular kind of pest. However, rotating between crops such as grains and legumes can make a particular pests become scarce or less populated.