Reptiles

DiversityDiversity

◦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/cold-blooded)

Good for reptiles—don’t have to eat to maintain body temp

DiversityDiversity

◦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"

◦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 retention1. 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

General Characteristics

Kingdom AnimaliaPhylum ChordataClass Reptilia

◦They are represented by four surviving orders:1. Crocodilia2. Rhynchocephalia3. Squamata4. Testudines

Classification

◦Order Crocodilia Ex: crocodiles, caimans and alligators23 surviving speciesBody shape: elongated, robust, reinforced skull and massive jaw muscle structure

Teeth in socketsFour-chambered heartCan vocalizeOviparous (eggs are guarded heavily by mother)

Will lay 20-50 eggs at a time

Classification

Male Crocodile courtship

◦Rhynchocephalia Ex: tuataras from New Zealand

2 surviving speciesLizard-like body formSlow-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 speciesMost 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, tortoisesApproximately 300 speciesEnclosed 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

Classification