In the hemogenic endothelium model of hematopoiesis the source of the adult hematopoietic stem cells (hscs) are which of the following?
a. hemangioblasts in the yolk sac
b. hemogenic endothelial cells of the aorta
c. hemangioblasts of the blood cells
d. angioblasts in the mesoderm

step 1 ammonium can be absorbed by plants, but some is converted into nitrates which are better for plants to absorb. this is called nitrification. 2. step 2 the deer eats the plants and uses the nitrogen-containing proteins for cell growth. 3. step 3 bacteria in the soil conduct nitrogen fixation to convert nitrogen gas from the atmosphere into ammonium. 4. step 4 some of the nitrates are absorbed back into plants, but denitrification breaks down the nitrates into nitrogen gas released back into the atmosphere. 5. step 5 nitrogen is found in the urine, which gets broken down into ammonium through the process of ammonification. 6. step 6 plants absorb the ammonium and begin assimilation, the process to add the nitrogen to protein.

answerwestern plateau,     central lowlands,     great dividing range;