The Energy-Requiring Steps of Glycolysis. In the first half of glycolysis, energy in the form of two ATP molecules is required to transform glucose into two three-carbon molecules.
The three main worm phyla are flatworms, roundworms, and segmented worms. Roundworms have a digestive tube that has two openings. Segmented worms have a closed circulatory system in which blood is enclosed in blood vessels. These are important steps in the evolutionary development of animals.
