Suppose you were asked, "What is a sponge?" Have you considered what type of animal sponges are and where and how they live?
Interestingly enough, sponges are animals that live in water. Most live on the ocean floor and in shallow coastal waters, but many also live in ponds, lakes, and streams. They attach themselves to rocks, the ocean floor, or other animals. You can recognize them by their unusual shape and size. They look like shrubs or small trees or vases, ranging from about two and a half centimeters to over one meter wide. These odd-looking objects can be seen in an array of colors: red, yellow, green, blue, black, white, and purple.
Sponges are invertebrates that contain cells organized for specific jobs. The feeding cells capture food, the coloring cells give protection, and the skeleton-forming celis provide physical support.
Sponges have openings on their surfaces called pores. These pores have an outer layer that opens and closes. Because of the large quantities of pores on their surfaces, sponges are classified as Porifera [Puit-RIHF-uh-ruh], which means "pore bearing." The sponge feeds on organisms that it filters out of the water through its pores.
Which title best states the main idea of the passage?
• 1. Why Pores Are Called Porifera
• 2. How Sponges Feed Through Their Pores
• 3. Characteristics of a Sponge
• 4. What is a Pore?