Answer:
D
Explanation:
The neuroendocrine system is made up of the cell in the body that ‘sit’ between the nervous system and the endocrine system. These cells are like the pituitary gland, islets cells of the pancreas, thyroids, and etcetera. They receive nerve impulses from nerves connected to them. The impulse then triggers them to release respective hormones into the blood.
<span>The nitrogen cycle could not exist without first nitrogen. The cycle is about this specific element which goes to show that if this element is not present then, there will not be any nitrogen cycle. Also, an important factor for the cycle is the presence of the bacteria and other microorganism which are needed for the fixation. </span>
<h2>540 million years ago
</h2>
Paleozoic.
Era immediately follows Precambrian It lasted about 4.5 billion years.
When did abundant fossil evidence first appear in the geologic record.
540 million years ago.
