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Animal and Biomes Basics Theme Unit

Vertebrate Classification: Phylum Chordata

Vertebrate Classification: Phylum Chordata
Reading Level
     edHelper's suggested reading level:   grades 6 to 8
     Flesch-Kincaid grade level:   8.03

Vocabulary
     challenging words:    further, digestion, connective, internal, invertebrate, characteristic, genus, respiration, plural, theirs, gravity, skull, divide, reproduce, circulation, connection

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Vertebrate Classification: Phylum Chordata
By Cindy Grigg 		  
1     Biologists have described more than one million different kinds of living things on Earth. In order to study them, scientists divide them into groups based on similar traits. One system of classification divides all living things into five different kingdoms. They are animals, plants, fungi, monera, and protista.
 
2     These five kingdoms are then divided into five smaller groups: phylum, class, order, family, genus, and species. The animal kingdom is divided into about thirty-five different phyla (plural of phylum), or major groups. The animal kingdom has more species than any other kingdom.
 
3     Although a jellyfish and a person may not look very much alike, they belong to the same kingdom. People and jellyfish are both classified as animals. Animals are many-celled organisms that must obtain their food by eating other organisms. In addition, most animals reproduce sexually and can move from place to place. Biologists look for these characteristics in deciding whether an organism is an animal.
 
4     One important characteristic used to classify animals is whether or not they have a backbone or spine. An animal that does not have a backbone is called an invertebrate. Jellyfish, worms, spiders, and insects are all invertebrates. Most animal species are invertebrates (about ninety-five percent of all animals).
 
5     Vertebrates are all animals that have a backbone. Vertebrates are in the phylum Chordata. Members of this phylum are called chordates. They all share some common characteristics. At some point in their lives, they have a notochord, a nerve cord, and slits in their throat area. The phylum name comes from the notochord, a flexible rod that supports the animal's back. Some chordates (lancelets) keep the notochord all their lives. Others have a notochord as larvae, but not as adults (tunicates). In vertebrates, part or all of the notochord is replaced by backbone. A few vertebrates have backbones made of cartilage (sharks). Cartilage is a connective tissue that is softer than bone, but flexible and strong. Most vertebrates have backbones made of hard bone.

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