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Biology. 31-1 Reptiles. What Is a Reptile?. What are the characteristics of reptiles?. What Is a Reptile?. What Is a Reptile? A reptile is a vertebrate that has dry, scaly skin, lungs, and terrestrial eggs with several membranes.

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biology
Biology

Copyright Pearson Prentice Hall

31 1 reptiles
31-1 Reptiles

Copyright Pearson Prentice Hall

what is a reptile
What Is a Reptile?

What are the characteristics of reptiles?

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what is a reptile4
What Is a Reptile?

What Is a Reptile?

A reptile is a vertebrate that has dry, scaly skin, lungs, and terrestrial eggs with several membranes.

These characteristics enable reptiles to live their entire lives out of water.

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what is a reptile5
What Is a Reptile?

Reptilian skin is dry and covered with thick, protective scales.

This prevents the loss of body water in dry environments.

The scaly layer of skin doesn’t grow, so it must be shed periodically as the reptile increases in size.

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evolution of reptiles
Evolution of Reptiles

Evolution of Reptiles

Reptiles were the first vertebrates that were not dependent on water for reproduction.

The first reptile fossil dates back to the Carboniferous Period.

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evolution of reptiles7
Evolution of Reptiles

Dinosaurs

During the late Triassic and Jurassic periods, a great adaptive radiation of reptiles took place.

The Mesozoic Era is often called the Age of Reptiles.

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evolution of reptiles8
Evolution of Reptiles

Triassic Reptiles

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evolution of reptiles9
Evolution of Reptiles

Dinosaur structure and behavior varied:

  • Ranged in size from small to enormous.
  • Ran on two legs or on four legs.
  • Ate leafy plants or other animals.
  • Some lived in small family groups.
  • Some may have had feathers.

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evolution of reptiles10
Evolution of Reptiles

All of dinosaurs belonged to one of two major groups:

  • Ornithischia, or “bird-hipped” dinosaurs
  • Saurischia, or “lizard-hipped” dinosaurs

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evolution of reptiles11
Evolution of Reptiles

At the end of the Cretaceous, a mass extinction occurred that killed the dinosaurs as well as other plant and animal groups.

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form and function in reptiles
Form and Function in Reptiles

Form and Function in Reptiles

How are reptiles adapted to life on land?

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Form and Function in Reptiles

Tough, scaly skin and the ability to control body temperature are two adaptations to terrestrial life.

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Form and Function in Reptiles

Adaptations that have contributed to the success of reptiles on land are:

  • well-developed lungs
  • a double-loop circulatory system
  • a water-conserving excretory system
  • strong limbs
  • internal fertilization
  • shelled, terrestrial eggs

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Form and Function in Reptiles

Body Temperature Control 

Reptiles are ectotherms.

Ectotherms are animals that rely on behavior to control body temperature.

To warm up, they bask in the sun or stay under water at night.

To cool down, they move to the shade or take shelter in underground burrows.

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Form and Function in Reptiles

Feeding 

Reptiles eat a wide range of foods.

  • Iguanas eat plants.
  • Snakes eat small animals, bird eggs, or other snakes.
  • Crocodiles and alligators eat fish and land animals.
  • Chameleons eat insects.

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Form and Function in Reptiles

Respiration 

Reptile lungs are spongy, allowing for a larger area of gas-exchange.

Many reptiles have muscles around the ribs that expand and collapse the chest cavity.

Most reptiles have two lungs, but certain species of snakes have just one lung.

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Form and Function in Reptiles

Circulation 

Reptiles have a double-loop circulatory system:

  • One loop brings blood to and from the lungs.
  • One loop brings blood to and from the rest of the body.

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form and function in reptiles19
Form and Function in Reptiles

Liver

Heart

Kidney

Cloaca

Lung

Digestive tract

Bladder

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Form and Function in Reptiles

Reptile hearts have two atria and either one or two ventricles.

  • Most reptiles have one ventricle with a partial septum that separates oxygen-rich and oxygen-poor blood.
  • Crocodiles and alligators have two atria and two ventricles.

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form and function in reptiles21
Form and Function in Reptiles

To body

From lungs

Right atrium

To lungs

Left atrium

From body

Incomplete division

Ventricle

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Form and Function in Reptiles

Excretion 

Urine is produced in the kidneys.

  • In some reptiles, urine flows in tubes directly into a cloaca.
  • In others, a bladder stores urine before it is expelled.

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Form and Function in Reptiles

Other reptiles convert ammonia into uric acid.

  • In the cloaca, urine is reduced to crystals of uric acid that form a pasty white solid.
  • By eliminating solid wastes, a reptile can conserve water.

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Form and Function in Reptiles

Response 

Reptilian brains are similar to amphibians.

Their cerebrum and cerebellum are more developed than other parts of the brain.

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Form and Function in Reptiles

Reptiles that are active in the day have complex eyes and see color well.

Many snakes also have an extremely good sense of smell.

Most reptiles have sensory organs in the mouth that detect chemicals when reptiles flick their tongues.

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Form and Function in Reptiles

Reptiles have simple ears with an external eardrum and a single bone that conducts sound to the inner ear.

Snakes can also pick up vibrations in the ground through bones in their skulls.

Some snakes can detect the body heat of their prey.

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Form and Function in Reptiles

Movement 

Reptiles with legs have large strong limbs.

Some have legs that are rotated further under the body, enabling them to carry more body weight.

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Form and Function in Reptiles

The legs and feet of many aquatic turtles have developed into flippers.

Reptiles’ backbones help accomplish much of their movement.

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Form and Function in Reptiles

Reproduction 

Most reptiles are oviparous, laying eggs that develop outside the mother’s body.

All reptiles reproduce by internal fertilization, in which the male deposits sperm inside the female’s cloaca.

After fertilization, the female’s reproductive system covers the embryo with several membranes and a leathery shell.

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Form and Function in Reptiles

The shell and membranes protect the embryo and prevent the egg from drying out.

This type of egg, an amniotic egg, is one of the most important adaptations to life on land.

An amniotic egg has four membranes—the amnion, the yolk sac, the chorion, and the allantois.

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Form and Function in Reptiles

The amnion is a fluid-filled sac that surrounds and cushions the developing embryo.

Amnion

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Form and Function in Reptiles

The chorion regulates the transport of oxygen and carbon dioxide between the surface of the egg and the embryo.

Chorion

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Form and Function in Reptiles

The yolk sac contains the yolk that serves as a nutrient-rich food supply for the embryo.

Yolk sac

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Form and Function in Reptiles

The allantois stores the waste produced by the embryo.

Allantois

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groups of reptiles
Groups of Reptiles

What are the four living orders of reptiles?

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groups of reptiles36
Groups of Reptiles

Groups of Reptiles

The four surviving groups of reptiles are:

  • lizards and snakes
  • crocodilians
  • turtles and tortoises
  • tuataras

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Groups of Reptiles

Lizards

Most lizards have four legs and clawed toes.

Most lizards have external ears and movable eyelids.

Some lizards have evolved into highly specialized forms.

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Groups of Reptiles

Snakes

Snakes have no legs.

Snakes have immovable eyelids and no external ear openings.

Snakes are efficient predators.

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Groups of Reptiles

Crocodilians

Crocodilians have long, broad snouts and a squat appearance.

They prey on animals such as fishes, deer, and even humans.

Females guard their eggs from predators and watch over their young after the eggs hatch.

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Evolution of Reptiles

Crocodilians live only where it is warm year-round.

Alligators and caimans live only in fresh water and are found almost exclusively in North and South America.

Crocodiles live in either fresh or salt water and are native to Africa, India, and Southeast Asia.

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Groups of Reptiles

Turtles and Tortoises

Turtles live in water.

Tortoises live on land.

A terrapin is a turtle that lives in water that is somewhat salty.

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Groups of Reptiles

Turtles and tortoises have a two-part shell built into the skeleton:

  • a dorsal part, or carapace
  • a ventral part, or plastron

The head, legs, and tail emerge from holes where the carapace and plastron join.

Tortoises and most turtles pull into their shells for protection.

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Groups of Reptiles

Tuataras

Tuataras are found only on a few islands off New Zealand.

They lack external ears and retain primitive scales.

They have a “third eye,” which is part of a complex organ located on top of the brain.

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ecology of reptiles
Ecology of Reptiles

Ecology of Reptiles

Many reptiles are in danger because of habitat destruction.

Humans hunt reptiles for food, for pets, and for their skins.

Laws protect some species, but more conservation efforts are needed to counteract their dwindling numbers.

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Most reptiles reproduce with

  • external fertilization and external development.
  • internal fertilization and internal development.
  • internal fertilization and external development in water.
  • internal fertilization and external development in shelled eggs.

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The yolk sac of a reptile egg functions as a

  • membrane that exchanges oxygen and carbon dioxide for the embryo.
  • membrane that stores wastes produced by the embryo.
  • source of nutrient-rich food for the developing embryo.
  • shock-absorbing fluid-filled sac protecting the embryo.

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Reptiles are

a. ectotherms.

b. endotherms.

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Reptiles with the most well-developed hearts include

  • turtles and alligators.
  • crocodiles and turtles.
  • crocodiles and alligators.
  • alligators and lizards.

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The two parts of a turtle or tortoise's shell are the

  • terrapin and plastron.
  • carapace and plastron.
  • carapace and terrapin.

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