Fishes, Amphibians, and Reptiles What Is a Vertebrate? Fishes Amphibians Reptiles Vertebrate History...

Fishes, Amphibians, and Reptiles

What Is a Vertebrate?

Fishes

Amphibians

Reptiles

Vertebrate History in Rocks

Table of Contents

Fishes, Amphibians, and Reptiles - What Is a Vertebrate?

Ancient Jawless Fish

Look backward in time, into an ocean 530 million years ago. There you see a strange-looking creature—a jawless fish—that is about as long as your index finger.

Fishes, Amphibians, and Reptiles - What Is a Vertebrate?

Characteristics of Chordates

This lancelet shows the characteristics of a chordate: a notochord, a nerve cord down its back, and gill slits.


Building VocabularyA definition states the meaning of a word or phrase by telling about its most important feature or function. After you read the section, reread the paragraphs that contain definitions of Key Terms. Use the information you have learned to write a definition of each Key Term in your own words.

Key Terms: Examples:

- What Is a Vertebrate?

chordate All members of this phylum are called chordates.

notochord The phylum name Chordata comes from the notochord, a flexible rod that supports a chordate’s back.

vertebra You can see in Figure 2 that the backbone is formed by many similar bones called vertebrae.

Key Terms: Examples:ectotherm

endotherm

An ectotherm is an animal whose body does not produce much internal heat.

The beaver is an example of an endotherm—an animal whose body regulates its own temperature by controlling the internal heat it produces.


Links on Vertebrates

Click the SciLinks button for links on vertebrates.

- What Is a Vertebrate?


End of Section:What Is a

Vertebrate?

Fishes, Amphibians, and Reptiles - Fishes

Characteristics of Fishes

Most fishes obtain oxygen through gills.

Fishes, Amphibians, and Reptiles - Fishes

Bony Fishes

A bony fish has jaws, scales, a pocket on each side of the head that holds the gills, and a skeleton made of hard bones.


Before you read, preview Figure 12. Then write two questions that you have about the diagram in a graphic organizer like the one below. As you read, answer your questions.

Previewing Visuals

Structure of a Fish

Q. What is a swim bladder?

A. A swim bladder is an internal, gas-filled sac that helps stabilize the fish at different depths in the water.

Q. What is the function of the tail fin?

A. It helps provide the power for swimming.

- Fishes


End of Section:Fishes

Fishes, Amphibians, and Reptiles - Amphibians

What Is an Amphibian?During its metamorphosis from tadpole to adult, a frog’s body changes dramatically.

Fishes, Amphibians, and Reptiles - Amphibians

Living on Land

Many adult amphibians have lungs, a heart with three chambers, and a double-loop circulatory system.


SequencingMake a cycle diagram like the one below that shows the different stages of a frog’s metamorphosis during its life cycle. Write each step of the process in a separate circle.

Frog Metamorphosis

Adult frog

Fertilized egg

Tadpole hatches.

Hind legs develop.

Front legs develop.

Tail is absorbed.

- Amphibians


More on The Frog Life Cycle

Click the PHSchool.com button for an activity aboutthe frog life cycle.

- Amphibians


End of Section:Amphibians

Fishes, Amphibians, and Reptiles - Reptiles

Adaptations for Life on Land

The membranes and shell of an amniotic egg protect the developing embryo.


Characteristics of a Lizard

This lizard, a Jackson’s chameleon, has many adaptations that help

it survive in its

environment.


The Sex Ratio of Newly Hatched Alligators

The temperature of the developing eggs of the American alligator affects the sex ratio of the young. (Sex ratio is the number of females compared with the number of males.)

- Reptiles



29.4ºC

Reading Graphs:

At which temperature(s) did only females hatch?

- Reptiles



The warmer the incubation temperature, the greater the proportion of males.

Drawing Conclusions:

What effect does the temperature of developing eggs have on the sex of the baby alligators?

- Reptiles



According to the graph, out of the 50 alligators that were incubated at 31.7ºC, about 40 (or 80%) were males. So 80% of 100 eggs (80) could be expected to hatch as males.

Calculating:

If 100 eggs developed at 31.7ºC, about how many of the young would be male?

- Reptiles


Extinct Reptiles–The Dinosaurs

Dinosaurs were the earliest vertebrates that had legs positioned directly beneath their bodies.


Main Idea

Detail Detail Detail

Identifying Main IdeasAs you read the information under the heading “Adaptations for Life on Land,” write the main idea in a graphic organizer like the one below. Then write three supporting details that further explain the main idea.

Reptiles are adapted to conserve water.

Reptiles have a thick, scaly skin that prevents water loss.

Reptile eggs have a shell and membranes that keep them from drying out.

A reptile’s kidneys concentrate wastes before excreting them so that little water is lost.

- Reptiles


More on Reptiles

Click the PHSchool.com button for an activity about reptiles.

- Reptiles


End of Section:Reptiles

Fishes, Amphibians, and Reptiles - Vertebrate History in Rocks

Interpretation of Fossils

Fossils most often form in layers of sedimentary rock.

Fishes, Amphibians, and Reptiles - Vertebrate History in Rocks

Interpretation of Fossils

The pattern of vertebrate evolution is branching.


Asking QuestionsBefore you read, preview the red headings. In a graphic organizer like the one below, ask a what or how question for each heading. As you read, write answers to your questions.

How do fossils form? Fossils form from imprints or the remains of organisms.

How are fossils interpreted?

Scientists examine fossil structure and make comparisons to present-day organisms.

Questions Answers

- Vertebrate History in Rocks


Links on Fossils

Click the SciLinks button for links on fossils.

- Vertebrate History in Rocks


End of Section:Vertebrate

History in Rocks


Graphic Organizer

The larvae of amphibians are adapted for life in water, and adult amphibians are adapted for life on land.

Larvae have tails for swimming; adults have

legs for walking.

Detail Detail Detail

Main Idea

Larvae have gills; adults have lungs.

Larvae have one-loop circulatory systems and two-chambered hearts; adults have two-loop

circulatory systems and three-chambered

hearts.


End of Section:Graphic Organizer

Fishes, Amphibians, and Reptiles What Is a Vertebrate? Fishes Amphibians Reptiles Vertebrate History...

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