1. The Reptile Body

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

14. 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

16. 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

17. 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

18. 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

19. 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