Paramecium feeds on bacteria and on many small organisms, with some types having chlorella that are responsible for creating some nutrients. Like other similar organisms, they have contractile vacuoles that contain water that release the water into the cell to combat osmotic changes in the environment. These organisms have an avoidance reaction, in which the cilia beat backward in order to avoid a barrier before restarting in a different direction to move out of the way of the barrier.
THE DIFFERENT ANIMAL PHYLA This section is a brief review of the different animal phyla. The Kingdom Animalia is large with organisms of many different unrelated animal organisms. Most of the phyla are included in this discussion: •
Nematoda—these are the roundworms, of which there are more than 80,000 species—15,000 of these are parasitic.
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Nematomorpha—this is a small group of parasitic nematodes that live partially inside the body cavity of arthropods. There are only about 350 species.
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Priapula—this is a very small phylum consisting of 18 species, the largest of which are carnivores.
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Kinorhyncha —this is a small phylum with just about 150 species, related to the nematodes.
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Loricifera—this is a newer phylum of microscopic organisms that have an exoskeleton called a lorica and a part called an introvert that extends and retracts the mouth.
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Onychophora—this is a small phylum that consists of the velvet worms. They are loosely connected to arthropods.
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Arthropoda—this is the largest animal phylum with about 3.7 million species of arthropods. They are defined as having chitin exoskeletons and include the arachnids (spiders), scorpions, centipedes, millipedes, insects, and crustaceans. The insects are the largest classification with 30 separate orders.
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