1. Explain the challenges and advantages of having internal gills over external gills for gas exchange?

2. Explain how increased stress levels can affect hormones which ultimately inhibit the immune system? Include all relevant glands and hormones in your discussion.

3. Describe, with the aid of your own diagrams, the process of how a human sperm is produced from a single 2N cell. Indicate the chromosomal content at all stages.

4. Describe how the three layers of the embryo are formed from a single layer of cells in the blastula.

5. Describe, in as much detail as possible, the path that a single blood cell will make when travelling from an artery in the stomach back tothat same artery by the shortest route possible. Include information about what is happening to that blood cell at the different locations (i.e., losing oxygen etc.). Use only information from the text.

6. Explain how a molecule of starch that you eat enters the blood stream.

7. In your own words, explain how vaccination works to protect someone against mumps?