Scholarship..............
Because the soil didn't have the same nutrients it has now due to lack of decomposition of other plants and animals.
<span>Basically, the body needs to know what it is defending against. Your body can still (usually) fight off infection, even without an immunization, but it takes longer. Basically, your body creates cells with a receptor for a specific disease. When this cell finds the disease it is programmed for, it will send out signals to the "killer" cells to come and kill it. If your body doesn't have the "seeker" cells, it can't fight off the infection until it does. The opposite end are autoimmune diseases, where your immune system starts attacking itself.
brainlest answer</span>
In the meaning of wave x it would be solid
Answer:
Closed the first one
Explanation:
In amphibians, reptiles, birds, and mammals, blood flow is directed in two circuits: one through the lungs and back to the heart, which is called pulmonary circulation, and the other throughout the rest of the body and its organs including the brain (systemic circulation).
most mammals, have closed cardiovascular systems. The two main circulation pathways in invertebrates are the single and double circulation pathways.
