There are about 5,000 species of sponges found throughout the world. Most sponges are found in oceans, although some groups are found in fresh waters such as lakes. They were the first group of animals that has specialized cells to do special jobs. However, the cells are not so advanced as to form tissues. Sponges live singly or in colonies.
Many sponges give off a toxic or poisonous substance. This is used to fight off enemies and poison them. However, some of the substances given off are used by humans as medicines. The skeleton of the sponge is used by man for sponges as well.
Some sponges appear green because algae clings to them. The algae provide oxygen for the sponge and the sponge provides carbon dioxide for the algae. When two living things live off of one another, it is called symbiosis
www.mcwdn.org
No comments:
Post a Comment