The appearance of fossils would the the answer.
Although there has been some scientific debate about what fossil strata should mark the beginning of this period, the "International Geological Congress" determined that the Cambrian period was approximately 543 million years ago of which the first appearance in the fossil record of worms that made horizontal burrows was discovered.
Running water both beach answers and valleys
Known as the cell’s “command center,” the nucleus is a large organelle that stores the cell’s DNA (deoxyribonucleic acid). The nucleus controls all of the cell’s activities, such as growth and metabolism, using the DNA’s genetic information. Within the nucleus is a smaller structure called the nucleolus, which houses the RNA (ribonucleic acid). RNA helps convey the DNA’s orders to the rest of the cell and serves as a template for protein synthesis.
Answer:
The bacterial flora in the intestines are essential to homeostasis in the body, they not only break down food so the nutrients can be absorbed, they produce vitamins like biotin and vitamin K and guard against harmful bacteria that enter the system. While your heart is a vital organ, the brain (and the nervous system that attaches to the brain) make up the most critical organ system in the human body. The digestive system ordinarily gets 20% to 25% of the oxygenated blood pumped out by the heart and the receptors in muscles provide the brain with information about body position and movement, the brain controls the contraction of skeletal muscle the nervous system regulates the speed at which food moves through the digestive tract.
