The Reptile Body

Characteristics of Reptiles

• Reptiles were the first vertebrates to live on land• Scales keep moisture inside – Reptiles eggs DO NOT dry out on land

• Live in a variety of different habitats – Tropical forests, des\serts, oceans, rivers, and lakes– Are NOT found in very cold regions because they are

cold-blooded

Characteristics of Reptiles

• All reptiles share the following characteristics– Bodies covered in scales – Clawed toes– Ectothermic (cold-blooded) metabolism– Lack feathers or any form of hair– An internal skeleton– A heart with a partially divided ventricle – Lungs– Reproduce Internally • Amniotic eggs

Reptile Movement and Response

• The following adaptations allow reptiles to live in dry environments – A strong skeleton– Claws– legs positioned under the body– highly developed vision

• Since Reptiles are cold-blooded this limits their habitat range

Endoskeleton• Reptiles have a strong skeleton made

of bone• Most reptiles have two pairs of limbs– Snakes and some lizards lack legs– Legs positioned under the body

allow reptiles to move faster and easier on land

• Reptiles have toes with claws– Use claws for climbing and digging – Enables reptiles to run quickly over

short distances

Sensory Systems: Vision• Vision is an important sense– Rely on sight to detect

predators and prey • Eyes of reptiles are very large

and have movable eyelids– Snakes and geckos lack

movable eyelids– Reptiles that are active at

night can see very well in the dark

Sensory Systems: Hearing

• Hearing is a very important sense organ to reptiles

• Sound waves first strikes the tympanum (ear drum) and are then transmitted to the inner ear – Snakes lack a tympanum – They detect ground

vibrations through the bones of their jaw

Sensory Systems: Jacobson’s Organ• Reptiles sticks their tongues

out to collect small particles from the air– The small particles come in

contact with the Jacobson’s Organ

– The Jacobson’s Organ is a specialized sense organ in the roof of the mouth of many reptiles, it is sensitive to odors

– Used to “taste” the environment

Sensory System

• Snakes are able to detect heat given off by warm-bloodied prey – Use heat sensitive pits

below each eye – The pits allow the snake to

detect the distance and direction of the prey

Body Temperature Control• Reptiles are ectothermic– They CANNOT heat their own body by using their

metabolism • A reptile’s body temperature is mostly

determined by the temperature of its environment – Reptiles may bask in the sun to warm up or seek

shade to cool down – At very low temperatures reptiles slow down and

may not be able to function

Respiration and Circulation

• The following adaptations allow reptiles to have more efficient respiration and circulation

– 1. Lungs with a large surface area

– 2. A heart that is almost completely divided into four chambers

Reptile Lungs

• Reptile lungs have many internal folds, which gives the lungs a large surface area for oxygen exchange – Strong muscles in the rib cage allow air to move in

and out of the lungs quickly, which increases lung efficiency

Reptile Heart

• The septum partly divides the ventricle into right and left halves – Enables a much better, but still incomplete,

separation of oxygen-rich and oxygen-poor blood– Oxygen is delivered to the body cells more

efficiently in reptiles than in amphibians

Reptile Reproduction• Reptile reproduction occurs through internal

fertilization– Many reptiles are oviparous: the young hatch from eggs

that are laid outside the mother’s body. – Some snakes are lizards are ovoviviparous: fertilized

eggs remain inside the female’s body for a long time and hatch inside the female• This protects the eggs from predators

– Most reptiles DO NOT care for their young• Alligators and crocodiles are an exception

Amniotic Eggs

• An amniotic egg contains both a water supply and food supply

• Amniotic eggs are key to a reptile’s success as a terrestrial animal – They are watertight

Amniotic Egg Structure• The shell and albumen protects

and cushions the embryo – Also a source of nutrients

• There are four membranes in the amniotic egg– 1. Amnion- cushions the embryo – 2. Yolk Sac- contains the embryo’s

main food supply, blood vessels attach here

– 3. Allantois- stores waste and is the embryo’s organ for gas exchange

– 4. Chorion- allows oxygen to enter the egg and carbon dioxide to leave the egg

Review Questions• 1. Identify seven characteristics of reptiles• 2. Describe how being ectothermic influences a

reptile’s lifestyle • 3. Explain how reptiles meet their need for

oxygen• 4. Summarize how the amniotic egg allows

reptiles to live on land • 5. Do you think a reptile that cares for its young

lays more or fewer eggs than a reptile that doesn’t care for its young? Explain