chapter 18: vertebrates
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Chapter 18: Vertebrates. Section 1 Chordates. Chordate Animals. 1. What is a chordate?. Animals with a backbone belong to a larger group of animals called chordates (KOR dayts). - PowerPoint PPT PresentationTRANSCRIPT
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Section 1Chordates
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• Animals with a backbone belong to a larger group of animals called chordates (KOR dayts).
• Three characteristics of all chordates are a notochord, a nerve cord, and pharyngeal pouches at some time during their development.
What is a chordate?
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• The notochord is a flexible rod that extends along the length of the developing organism.
• Pharyngeal pouches are slitlike openings between the body cavity and the outside of the body.
What is a chordate?
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• Scientists classify the 42,500 species of chordates into smaller groups. The animals within each group share similar characteristics, which may indicate that they have a common ancestor.
Vertebrates
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• Vertebrates have an internal system of bones called an endoskeleton. Endo- means “within.”
Vertebrates
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• The vertebrae, skull, and other bones of the endoskeleton support and protect internal organs.
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• Most vertebrate body temperatures change as the surrounding temperature changes.
Body Temperature
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• These animals are ectotherms (EK tuh thurmz), or cold-blooded animals.
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• Humans and many other vertebrates are endotherms (EN duh thrums), or warm-
blooded animals. Their body temperature doesn’t change with the surrounding temperature.
Body Temperature
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Body Temperature
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• Changes of more than a degree or two usually indicate an infection or overexposure to
extreme environmental temperatures.
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Fish
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• Fish have fleshy filaments called gills where carbon dioxide and oxygen are exchanged.
• Fish are ectotherms that can be found in almost all bodies of water, including
warm desert pools and the subfreezing Arctic Ocean.
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• Most fish have pairs of fanlike fins.
Fish
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• The top and the bottom fins stabilize the fish. Those on the sides steer and move the
fish. The tail fin propels the fish through the water.
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Fish
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• Most fish have scales. Scales are thin structures made of a bony material that overlap like shingles on a house to cover the skin.
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• Scientists classify fish into three groups—bony, jawless, and jawed cartilaginous (kar tuh LA juh nuhs).
Types of Fish
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• Bony fish have skeletons made of bone, while jawless fish and jawed cartilaginous fish have endoskeletons made of cartilage.
• Cartilage (KAR tuh lihj) is a tough, flexible tissue that is similar to bone but is not as hard or brittle.
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• About 95 percent of all fish have skeletons made of bone.
Bony Fish
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• The body structure of a typical bony fish is shown here.
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Bony Fish
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• An important adaptation in most bony fish is the swim bladder. This air sac helps control the depth at which the fish swims.
Bony Fish
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Bony Fish
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• As the swim bladder fills with gas, the fish rises in the water.
• Then the gas leaves the bladder, it deflates and the fish sinks lower in the water.
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• Most bony fish use external fertilization (fur tuh luh ZAY shun) to reproduce.
Bony Fish
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• Females release large numbers of eggs into the water.
• Then, a male swims over the eggs, releases the sperm into the water, and many eggs are fertilized.
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• Jawless fish have scaleless, long, tubelike bodies; an endoskeleton made of cartilage; and a round, muscular mouth without a jaw.
Jawless and Jawed Cartilaginous Fish
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• One type of jawless fish, the lamprey, attaches itself to a larger host fish using its strong mouth and toothlike structures.
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• Sharks, skates, and rays are jawed cartilaginous fish.
Jawless and Jawed Cartilaginous Fish
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• Jawed cartilaginous fish have rough, sandpaperlike scales and movable jaws.
• Many sharks have sharp teeth made from modified scales.
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11Section CheckSection Check
Question 1_______ is the internal system of bones in vertebrates.
AnswerThe answer is endoskeleton. The endoskeleton supports and protects the internal organs.
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11Section CheckSection Check
Question 2Which is the largest group of vertebrates?
A. catsB. dogsC. fishD. humans
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11Section CheckSection Check
AnswerThe answer is C. Fish are ectotherms and live in water.
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11Section CheckSection Check
Question 3This illustration shows a typical body structure of what classification of fish?
A. bonyB. cartilaginousC. jawlessD. scale less
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11Section CheckSection Check
AnswerThe answer is A. About 95 percent of all fish have skeletons made up of bone.