Because the soil didn't have the same nutrients it has now due to lack of decomposition of other plants and animals.
Since the other answer got deleted, i'll just answer it for you.
a sinoatrial node is the main pacemaker that begins each heartbeat located in the junctions of superior vena cava and the right atrium. It signals from the node that spread through the atria and determines the heart rates.
Answer:
<em>The correct answer is C) The organs mature</em>
Explanation:
During the 3rd trimester, the baby continues with its development. Structures like the bones have completely formed but are soft. The baby is capable of opening and closing its eyes. During the 3rd trimester, the organs of the baby are fully mature and can carry out their own functions. By the end of the third- trimester, the baby turns in head- down position. Hence, the correct option is C.
Alleles are a variant of genes. Each human has two