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Introduction to

ANIMALS: VERTEBRATES

New Mexico Museum of Natural History & Science • Proyecto Futuro

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New Mexico Museum of Natural History & Science • Proyecto Futuro

Vertebrates • Background Information

BACKGROUND INFORMATION—VERTEBRATES
Vertebrates are a relatively small group of organisms under the phylum Chordata (see chart below). Chordates were the firstanimals to have a central support column and nerve cord running along their back. In vertebrates, this characteristic is called a backbone. The vertebrate backbone is part of a more extensive, internal skeleton. By comparison, invertebrates, such as insects, have an exoskeleton that helps to support their small size and weight. The weight of aquatic organisms is supported by the water. Larger animalsthat live on land need additional support, however. This support comes from the endoskeleton made of bones.

Classification of living chordates within the animal kingdom
Kingdom Animalia Phylum Cnideria (coral, anemones) Phylum Platyhelminthes (flatworms—includes planaria and tapeworms) Phylum Nematoda (roundworms—many are parasitic) Phylum Mollusca (snails, clams, squid) Phylum Annelida(segmented worms) Phylum Arthropoda (insects, spiders, crustaceans) Phylum Echinodermata (sea stars, starfish) Phylum Chordata Subphylum Vertebrata (vertebrates) Class Chondrichthyes (cartilaginous fish) Class Osteichthyes (bony fish) Class Amphibia (amphibians) Class Reptilia (reptiles) Class Aves (birds) Class Mammalia (mammals) About 500 million years ago, the ancestors of the subphylum Vertebratabegan to evolve into fish, amphibians, reptiles, birds, and mammals. Each developed different characteristics as they adapted to their differing environments, but they all share some characteristics in common.

New Mexico Museum of Natural History & Science • Proyecto Futuro

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Vertebrates • Background Information

Vertebrate characteristics:
• Vertebrates have a definite head,well-developed backbone of vertebrae, and welldeveloped brain. • Vertebrates have an internal support system called an endoskeleton. With an endoskeleton, an animal’s support system can grow as the animal grows rather than needing to be shed like an insect’s exoskeleton. • Muscles are attached and anchored to the strong, supportive backbone. The muscles and bones work together as levers to create preciseand efficient movements. • Rather than traveling through a dispersed net of nerves found in most invertebrates, nerve “messages” in vertebrates are quickly shuttled up and down the central “highway” of the spinal cord to a brain. • Vertebrates have complex circulatory systems. A vertebrate circulatory system includes a heart that pumps blood through blood vessels to all parts of the body. Theblood picks up oxygen from the respiratory organs (lungs or gills) and the oxygen is carried to all the cells of the body. The cells use the oxygen to make energy from food. Carbon dioxide is formed as a waste product, then released into the blood where it is carried back to the respiratory organs and expelled. The chemical process of using oxygen to convert food into energy is called respiration. •Vertebrates have complex digestive systems that include a mouth, stomach, and intestines. Each organ is specialized to efficiently break down food into nutrients that the cells need.

Major groups of vertebrates
Bony Fish Bony fish belong to the scientific class Osteichthyes (pronounced “os-tee-ick-thees”), the largest class of vertebrates. Their bodies are highly adapted for the underwaterenvironment they inhabit. Bony fish have gills that collect dissolved oxygen from the water. By opening and closing their mouths, water moves over the gills and the blood collects the oxygen from the gills. The blood is then pumped throughout the body by a two-chambered heart. (Humans have a four-chambered heart). Most bony fish need water to breathe,
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