Reptiles
Diversity
 Diversity
◦ Found on every continent but Antarctica
◦ Mainly found in tropics and subtropics
◦ Produce some heat
 Do not generate enough to maintain
constant body temp (still ectothermal/coldblooded)
 Good for reptiles—don’t have to eat to
maintain body temp
Diversity
 Diversity
◦ Reptiles included amniotes – those
animals who produce a shelled, amniotic
egg
 Do NOT INCLUDE birds and mammals
◦ Examples include:
 Crocodiles, alligators, lizards, snakes, and
turtles, Komodo dragon
◦ Grouped together as the class Reptilia
 Latin repere means "to creep"
General Characteristics
◦ Reptiles are tetrapods
 Vertebrates with four legs
◦ Contain tough keratinized skin
 Provides protection against injury
 Scales or bony plates (well-developed dermal layer)
 Contain chromatophores
◦ Excretory system
 Two small kidneys.
 Uric acid is the main waste product.
General Characteristics
◦ Contain powerful jaws
 Desgined for applying crushing or gripping
force
 Used to kill/capture prey
 FYI: Fish/Amphibian jaws designed for quick
closure (with little pressure/force)
 Reptile muscles (in jaw) are larger, longer
and arranged to apply a strong grip
General Characteristics
◦ Circulatory system
 Most reptiles have closed circulation
 Contain a three-chamber heart
 Consisting of two atria and one ventricle.
 There is little mixing of oxygenated and
deoxygenated blood in the three-chamber
heart.
General Characteristics
◦ Organs for water retention
1. Metanephric kidneys:
 excretes uric acid or urea which allows them to
occupy terrestrial habitats
2. Salt glands:
 Located near nose/eyes
 Secretes a salty fluid
◦ All reptiles have better body support
and more efficiently designed limbs
for travelling on land
General Characteristics
 Circulatory
system
◦ Exceptions to these characteristics:
 Crocodilians have a complicated four-chamber
heart
 This heart is capable of becoming a functionally
three-chamber heart (during dives)
 Some snake and lizard species (e.g., monitor
lizards and pythons) have three-chamber
hearts that become functional four-chamber
hearts (during contraction)
General Characteristics
 Respiratory
system
◦ All reptiles breathe using lungs.
 VERY well developed lungs
 Only a few use skin to breathe (sea snakes)
◦ Most reptiles do NOT have a muscular
diaphragm (like mammals)
 Crocodilians have a muscular diaphragm
◦ Turtles & Tortoises.
 Aquatic turtles have developed more permeable skin,
and even have gills in their anal region
General Characteristics

Nervous system
◦
◦
◦
◦
◦
◦
Advanced nervous system compared to amphibians.
12 pairs of cranial nerves.
Hearing is underdeveloped
All other senses are highly developed
Small brain (but, cerebrum is large)
Contain Jacobson’s organ
 Specialized organ for smell (odors carried to this organ via
the tongue)
General Characteristics

Reproduction system
◦ Most reptiles reproduce sexually.
◦ Asexual reproduction has been identified in in six
families of lizards and one snake.
◦ No larval stages.
◦ Internal fertilization (copulatory organs)
 Sperm – testes, Egg - ovaries
General Characteristics

Reproduction system, cont.
◦ Contain amniotic egg
 Permits rapid development of large young in
relatively dry environments
 Provides nourishment for growing embryo
 Provides protection (shell) from environment
 Allows for sufficient gas exchange
 Reduces water loss
Classification
 Kingdom Animalia
 Phylum
Chordata
 Class Reptilia
◦ They are represented by four surviving
orders:
1.
2.
3.
4.
Crocodilia
Rhynchocephalia
Squamata
Testudines
Classification
◦ Order Crocodilia
Male
Crocodile
courtship
 Ex: crocodiles, caimans and alligators
 23 surviving species
 Body shape: elongated, robust, reinforced skull
and massive jaw muscle structure
 Teeth in sockets
 Four-chambered heart
 Can vocalize
 Oviparous (eggs are guarded heavily by
mother)
 Will lay 20-50 eggs at a time
Classification
◦ Rhynchocephalia
 Ex: tuataras from New
Zealand
 2 surviving species
 Lizard-like body form
 Slow-growing animals that
live in burrows
 VERY good eyesight (have
cornea, lens and retina)
Classification
◦ Squamata
 Ex: lizards, snakes, (specific ex: gila
monster, python, monitor lizard)
 Approximately 7,600 species
 Most diverse group of reptiles
 Kinetic skull (mobile/moveable)
 May contain fangs (with poison)
 May contain heat-sensing organs (pit
organs – in pit vipers)
Classification
◦ Testudines
 Ex: turtles, tortoises
 Approximately 300 species
 Enclosed in shells consisting of carapace
and plastron (breastplate)
 No teeth, but contain keratinized plates
inside mouth for gripping food
 Oviparous
 Nest temperatures determine sex of offspring
 Low temp = males, high temp = females