2. Interstitial fluid fills the space between the cells of the internal environment of vertebrates. This fluid exchanges nutrients and wastes with the blood contained in microscopic vessels called capillaries.

3. Homeostasis - The steady-state physiological condition of the body.

4. Negative feedback is a mechanism of homeostasis, whereby a change in a physiological variable that is being monitored triggers a response that counteracts the initial fluctuation. It prevents small changes from becoming too large. An example is a thermo

9. When pepsinogen, which is secreted by epithelial cells, is activated, it becomes the enzyme pepsin upon exposure to the acid in gastric juice. Pepsin initiates the breakdown of food proteins

7. Major phyla, such as Cnidaria and Platyhelminthes, use a gastro vascular cavity for digestion.

12. The small intestine absorbs most of the digestive materials, while the large intestine absorbs the remainder of the materials and reabsorbs most of the water.

5. Suspension feeders are mostly aquatic animals that sift small food particles from the water. Substrate-feeders, such as leaf miners, live in or on their food source, eating their way through the food. Fluid-feeders make their living by sucking nutrient-rich fluids from a living host. Bulk-feeders eat relatively large pieces of food by either killing their prey or tearing off pieces of meat or vegetation by using tentacles, claws, fangs, jaws, or teeth.

-Carbohydrates are monosaccharides or simple sugars that are the basic components of more complex polymers. Theses sugars can be eff

Some common words found in the essay are:
Study Guide, Cnidaria Platyhelminthes, gastric juice, , amino acids, efficiently absorbed, secreted epithelial cells, acids absorbed, hydrolytic enzymes, enzyme pepsin, secreted epithelial, salivary amylase, food vacuoles, intestine absorbs,
Approximate Word count = 708
Approximate Pages = 3 (250 words per page double spaced)