Chapter 22 the parade of vertebrates
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Chapter 22- The Parade of Vertebrates. Kingdom Animalia Phylum Chordata Subphylum Vertebrata Fishes (jawless and jawed) Amphibians Reptiles Birds Mammals. The Vertebrate Family Tree. Fishes Dominate the Sea. Fishes constitute about half of all vertebrates

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Chapter 22 the parade of vertebrates l.jpg
Chapter 22- The Parade of Vertebrates

  • Kingdom Animalia

    • Phylum Chordata

      • Subphylum Vertebrata

        • Fishes (jawless and jawed)

        • Amphibians

        • Reptiles

        • Birds

        • Mammals

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Fishes Dominate the Sea

  • Fishes constitute about half of all vertebrates

    • They are are the most diverse and successful group of vertebrates

      • They provided the evolutionary base for invasion of land by amphibians

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Characteristics of Fishes

  • Fishes vary in size, shape, color and appearance

  • However, they all share these four characteristics

    • 1. Gills

      • Used to extract dissolved oxygen gas from water

    • 2. Vertebral column

      • An internal skeleton with a spine surrounding the dorsal nerve cord

    • 3. Single-loop blood circulation

      • Blood flow: Heart  Gills  Body  Heart again

    • 4. Nutritional deficiencies

      • Inability to synthesize the aromatic amino acids

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The Evolution of Jaws

  • Jaws addressed two challenges faced by predators

    • 1. How to grab and hold prey

    • 2. How to pursue prey

  • Jaws evolved from arch supports (about 410 mya)

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The Evolution of Jaws

  • The earliest jawed fishes had small bodies covered with protective spines

    • They had internal skeletons made of cartilage

  • Later, large jawed fishes called placodermsevolved

    • These had massive heads with heavy bony plates

  • Spiny fishes and placoderms are extinct now

    • All jawed fishes today are either sharks or bony fishes

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  • The Class Chondrichthyes adopted a light skeleton made up of strong, flexible cartilage

  • Skates and rays are flattened sharks that are bottom-dwellers

Blue shark

  • Have the most advanced fish reproduction system

  • Shark eggs are fertilized internally

    • About 40% lay fertilized eggs

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Fig. 22.12

Bony Fishes

  • The Class Osteichthyes adopted a heavy internal skeleton made of bone

  • Serves as base for attachment of strong muscles

  • Regulation of buoyant density occurs via a swim bladder

  • By adjusting the amount of gas in it, fish rise up or down

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Bony Fishes

  • The most successful of all vertebrates

    • Of the ~ 30,800 species of living fishes, ~30,000 are bony fishes

Korean angelfish

  • Lateral line system

    • Detects changes in water pressure

  • Operculum

    • Covers gills

      • Its flexing pumps water over the gills

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Red-eyed tree frog

Amphibians Invade the Land

  • Amphibians are direct descendants of fishes

  • They are the first vertebrate to walk on land

  • They include

    • Frogs

    • Toads

    • Salamanders

    • Caecilians

  • About 4,850 species of

    amphibians exist today

    • Class Amphibia

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Fig. 22.15 Evolution of legs

Characteristics of Amphibians

  • 1. Legs

    • Found in frogs and salamanders, but not in Caecilians

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Characteristics of Amphibians

  • 2. Lungs

    • Provide a more efficient means of respiration than gills

  • 3. Cutaneous respiration

    • Respiration directly across the skin supplements the use of lungs

  • 4. Pulmonary veins

    • Two large veins that return aerated blood to the heart for repumping

  • 5. Partially divided heart

    • Separates the blood circulation into two separate paths

      • Pulmonary and systemic

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Reptiles Conquer the Land

  • Reptiles replaced amphibians as the dominant terrestrial vertebrates

  • Among the most important reptile characteristics are:

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  • Chorion:Allows O2 entry

  • Amnion: Fluid-filled cavity

  • Yolk sac: Provides food

  • Allantois: Excretes waste

  • 2. Dry skin

    • Covers body and prevents water loss

  • 3. Thoracic breathing

    • Increases lung capacity

  • Plus, leg arrangement to better support body weight

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Birds Master the Air

  • Birds evolved from small bipedal dinosaurs about 150 mya

  • Birds still retain many reptilian characteristics

  • 1. They lay amniotic eggs

  • 2. They have reptilian scales on feet and lower legs

  • So what distinguishes birds from living reptiles?

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  • 1. Feathers

    • Derived from reptilian scales

    • Lightweight and easily replaced when damaged

  • 2. Flight skeleton

    • Bones are thin and hollow

    • Have a keeled breastbone (the wishbone)

    • Have a fused collarbone

  • Birds, like mammals, are endothermic

    • However, they maintain body temperatures much higher than most mammals

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Fig. 22.20

History of Birds

  • The oldest bird fossil is that ofArchaeopteryx

  • Had teeth and solid bones

  • By the early Cretaceous period, a diverse array of birds had evolved

  • About 8,600 species of birds exist today

    • Class Aves

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Mammals Adapt to Colder Times

  • Mammals (class Mammalia) evolved with dinosaurs about 220 mya

  • They share three characteristics with mammals today

    • 1. Mammary glands

      • Females have mammary glands which produce milk

    • 2. Hair

      • Keratin-made filaments that provide insulation

    • 3. Middle ear

      • Three middle ear bones that amplify vibration

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History of Mammals

  • Over 4,500 species of mammals exist today

    • Almost one-quarter are bats!

  • There are only 233 known species of primates

  • Humans evolved less than 2 mya

    • There have been at least three species

      • Only Homo sapiens is alive today!

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Other Characteristics of Modern Mammals

  • Endothermy

    • Allows colonization of severe environments

    • Depends on

      • 1. More efficient blood circulation

        • Provided by the four-chambered heart

      • 2. More efficient breathing

        • Provided by the diaphragm

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Other Characteristics of Modern Mammals

  • Placenta

  • Characteristic of most mammals

  • Brings the bloodstream of mother and fetus into close contact

  • The two don’t mix

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Other Characteristics of Modern Mammals

  • Teeth

  • Reptiles have homodont dentition

    • Teeth are all the same

  • Mammals have heterodont dentition

    • Teeth are of different types specialized for different feeding types

  • An animal’s diet may be determined by examination of its teeth

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Other Characteristics of Modern Mammals



Incisors dominate

Incisors serve as specialized weapons


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Other Characteristics of Modern Mammals

  • Hooves and horns

    • Hooves are specialized keratin pads on the toes of horses, cows and other running mammals

    • Horns of cattle, sheep, and antelope are composed of a core of bone surrounded by keratin

      • The horn is not shed

    • Deer antlers are made up of bone, not keratin

      • Male deer grow and shed a set each year

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Today’s Mammals

  • Monotremes: Egg laying mammals

  • The only living examples

    • Duck-billed platypus

    • Two species of echidna (spiny anteater)


  • Have reptilians and mammalian features

  • Females lack well-developed nipples

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Today’s Mammals

  • Marsupials: Pouched mammals

  • Fertilized egg is surrounded by chorion and amniotic membranes, but no shell

  • The embryo is nourished by an abundant yolk

  • After embryo is born, it crawls into the marsupial pouch

    • It latches onto a nipple and continues its development

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Today’s Mammals

  • Placental mammals

  • Produce a true placenta

    • Nourishes the embryo throughout its entire development

    • The placenta forms from both fetal and maternal tissue


  • Most species living today are in this group