The Different Animal Phyla

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.

• Nematomorpha—this is a small group of parasitic nematodes that live partially inside the body cavity of arthropods. There are only about 350 species.

• Priapula—this is a very small phylum consisting of 18 species, the largest of which are carnivores.

• Kinorhyncha —this is a small phylum with just about 150 species, related to the nematodes.

• 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.

• Onychophora—this is a small phylum that consists of the velvet worms. They are loosely connected to arthropods.

• 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.

• Tardigrada—a minor phylum of microscopic animals that live in damp or aquatic habitats. Each has a head, four segments, each having two legs.

• Sipuncula—this is a minor phylum with just about 150 species of tube-like marine animals that have tentacles.

• Mollusca—this is a large phylum of mostly aquatic animals. They have a mantle and a muscular foot with a radial teeth band and a shell. There are 50,000 to 150,000 species in this phylum.

• Annelida—these are the terrestrial segmented worms with at least 15,000 different species.

• Ectoprocta—this is an aquatic phylum that consists of 5000 different species.

• Phoronida—this is a very small phylum with just 12 species that build tubes made of chitin.

• Nemertea—these are aquatic unsegmented ribbon worms, living mostly in aquatic regions.

• Platyhelminthes—these are the flatworms, also a large phylum. It includes the tapeworms and parasitic flukes.

• Rotifera—these are the rotifers that live in fresh and seawater.

• Brachiopoda—these are the lamp-shells that have only 350 living species. They are bivalves that have different interiors than the typical bivalves seen in

Mollusca.

• Entoprocta—this is a small phylum of sessile marine animals.

• Gastrotricha—these represent just 700 species of aquatic animals.

• Cnidaria—this is a large phylum of sea anemones, corals, jellyfish, and hydroids.

• Ctenophora—these are the comb jellies of which there are just 80 living species.

• Xenacoelomorpha—this is a new phylum consisting of minor deuterostomes.

• Echinodermata—this is a large phylum including organisms with radial symmetry, such as the sea urchins, starfi sh, sand dollars, and sea cucumbers.

• Hemichordata—these involve the acorn worms and other marine organisms.

• Chordata—this is the phylum that contains the vertebrates. This is considered by some to be a superphylum, containing the tunicates, the lancelates, and the “Craniata” or Vertebrata, the vertebrates. Under the subphylum Vertebrata, there are these classes:

• Agnatha—the jawless fishes

• Chondrichthyes—the cartilaginous fishes

• Osteichthyes—the bony fishes

• Amphibia—the amphibians

• Reptilia—the reptiles

• Aves—the birds

• Mammalia—the mammals