We all have different needs. If you were asked what they were you might talkabout the need to buy a motor bike, to have enough money to go out on Friday night or to buy some new clothes. Water affects all of our lives in many different ways but it is probably something which is not instantly associated with your needs because it is taken for granted. Think how many times a day you use a tap, not just for washing your hands but also for making a cup of tea or coffee, for cooking, washing clothes, cleaning, running heating systems, washing-up and, of course, for flushing the toilet. Imagine what it would be like if water was not readily available. Perhaps the best way is to think of a seed and the ingredient necessary for it to germinate and grow - water. Like that seed we depend upon water but not only in its capacity as a necessity to support our existence but also for developing our standard of living. For example, in a modern home water must come into the house. We may have access to it both upstairs and downstairs. Water may be used in the heating system, the shower in the bathroom and for the washing machine. The demand for water has risen steadily over the last ten years, with the greater use of domestic appliances such as dishwashers and the installation of garden watering systems all adding to this demand.

1. What are poriferans?

2. How do sponges live?

3. What is the typical shape of poriferans?

4. How does water move inside sponges? What is the function of the pores in these animals?

5. How do sponges try to protect themselves againstenvironmental dangers? Is this method efficient or rudimentary?

6. What are the main cells that compose poriferans?

7. What is characteristic of poriferan digestion?

8. How are animals divided according to their type of digestive process?

9. How are gases exchanged in sponges?

10. Do sponges have nervous, circulatory and excretory system?