Reptiles

Characteristics of a Reptile Vertebrate

animals Lungs Scaly skin Amniotic egg

Characteristics of Reptiles – Adaptations to life on land

More efficient lungs and a better circulatory system for life away from water

Scaly skin provides protection against the elements and desiccation

The amniotic egg protects against desiccation

Reptile Lungs- Another Adaptation to Life on Land

A more efficient respiratory system

Reptiles use two efficient lungs (except snakes – they only have one long functional lung that fits their bodies, the other is vestigial)

Excretion Kidneys produce urine

in the form of uric acid Uric acid crystallizes

when concentrated, and is eliminated as a white paste (like birds)

Urine is either passed out directly through the cloaca, or stored in the urinary bladder where water is further reabsorbed

Scaly SkinScaly Skin An adaptation to life An adaptation to life

out of waterout of water WaterproofWaterproof Dry, leatheryDry, leathery Protective scalesProtective scales Must be moltedMust be molted

Watertight Skin

Reptile are covered by thick, dry, scaly skin that prevents water loss

Cells with a high keratin content Lipids and proteins in the skin make it watertight

conserving water and guarding against injury, infection and wear and tear

Amniotic Egg – Reptiles and Birds

Reptile eggs have a leathery shell

Has several membranes

Contains yolk rich in nutrients for embryo

Amniotic Egg Membranes Amnion – thin

membrane holds the fluid the embryo floats in

Yolk sac – holds the yolk (fatty food) for the developing embryo

Allantois – holds embryos nitrogenous wastes

Chorion – surrounds all the other membranes; protects embryo

The Amniotic Egg – adaptation to life on land

Amphibians are not able to move away from the water because their eggs would desiccate

Reptiles eggs prevent desiccation

Reptile Feeding

Ex. 1: Iguana Herbivores – tear

plants using teeth and jaws

Have long digestive systems

CarnivoresCarnivores

Snakes – have extendible jaws to swallow their prey whole.

Carnivores Some snakes

have a diet of eggs exclusively.

They swallow the egg whole, pierce the shell with a specialized section of the vertebrate, suck out the insides and regurgitates the shell

Carnivores

The king cobra eats other snakes

Breathing TubeBreathing Tube

Carnivores

Monitor lizard – kills prey with sharp teeth and powerful jaws

Carnivores Chameleons –

have long sticky tongue that they flip out to catch flying insects

..

Nervous SystemsNervous SystemsFrog Brain Alligator BrainFrog Brain Alligator Brain

Larger Larger cerebrum/ cerebrum/ cerebellum cerebellum than the than the amphibiansamphibians

Daytime Daytime reptiles have reptiles have good color good color vision: vision: turtles can turtles can see color see color better than better than humanshumans

Excellent Sense of Smell - Excellent Sense of Smell - SnakesSnakes Have pair of Have pair of

nostrilsnostrils Also have special Also have special

organs organs (vomeronasal (vomeronasal organs) on roof of organs) on roof of mouthmouth

Tongue picks up Tongue picks up chemicals and chemicals and brings them to the brings them to the vomeronasal vomeronasal organs to “taste” organs to “taste” the airthe air

Hearing Most lizards have

simple ears like an amphibian: external tympanum, single bone to transfer sound to inner ear . (we have an internal tympanum and 3 bones)

Snakes have no ears and are deaf – they “hear” the vibrations from the ground

Hearing - tortoises

Tortoises do not have a tympanum, but have a sound-conducting patch of skin on their head.

A “Red Ear Slider” turtle

Heat Sensors Pit vipers are able to detect heat, to obtain a temperature image of

their environment Normal view Infrared view Combined view

Pit vipers

Snakes - movementSnakes - movement

Snakes press their ventral scales against the ground

Muscles around the ribs expand and contract in waves causing the s-shaped movement

Movement

A snake has a backbone of 100 to 400 vertebrae, each of which has a pair of ribs attached.

- Providing the framework for thousands of muscles

The interaction of bones, muscles, and skin enables asnake to move in one of three basic ways:

1. Lateral undulation 2. rectilinear movement 3. side winding.

Gecko – suction cup toesGecko – suction cup toes

Geckos have special Geckos have special flaps of skin on its flaps of skin on its toes – creating very toes – creating very sticky appendagessticky appendages

Reptile ReproductionReptile Reproduction

Most have Most have internal internal fertilizationfertilization

Penis delivers Penis delivers sperm into sperm into cloaca of cloaca of femalefemale

Reptile ReproductionReptile Reproduction

Internal fertilizationInternal fertilization Male inserts penis Male inserts penis

into female’s cloacainto female’s cloaca Female’s body coats Female’s body coats

the embryos in the embryos in protective shell, with protective shell, with membranes and yolk membranes and yolk sacsac

Reptile Reptile ReproductionReproduction

Most reptiles are Most reptiles are oviparousoviparous

Some provide minimal Some provide minimal carecare

Modern Reptiles

Reptiles are classified into 16 orders, 12 that are extinct. - 4 surviving-6, 000 species Reptiles occur worldwide except in coldest regions - Human intervention-major impact 4 living orders of Class Reptilia: - 1. Rhynchocephalia, - 2. Chelonia, - 3. Crocodilia, - 4. Squamata

Rhynochocephalia

Only living species- Sphenodon punctatus- the tuatara

-  Inhibit islands of coast of New Zealand

- Resembles a large lizard about 60 cm long

- Has an inconspicuous third eye on top of its head- parietal eye- functions as a thermostat- protects from overheating

- Active at low temperatures and feed at night on insects, worms and small animals

Chelonia Order consists of about 265

species of turtles and tortoises - Tortoise are terrestrial Chelonia

(Galapagos tortoises) - Turtles- chelonians that live in

water - Body covered by a shell made

of hard plates- 2 parts- a carapace and plastron

- Shape is modified for variety of ecological demands

- retract heads, swimming - Forelimbs of a marine turtle

have evolved into flippers and freshwater turtles have webbed toes

- Migratory behavior of sea and river turtles

-return to land to lay eggs

Crocodilia Order composed of 20 species

of large lizard-shaped reptiles- crocodiles, alligators, caimans and gavials 

- Descendants of archosaurs Crocodilians live in or near

water in tropical/ subtropical regions of the world

- Crocodiles- nocturnal animals; Africa, Asia and Americas

-  Alligators - China and southern U.S.

- Caimans- Central America- some in Florida

- Gavials- eat fish; long and slender snout- live only in Burma and India

Carnivorous- hunt by stealth- features adapted for this behavior

  - Eyes on head, nostrils on top of snout

-see and breathe while in water

- Valve to prevent water from entering air passage

- Parental care- both parents care for young by carrying in jaws until development

Squamata

Order consists of 5,640 species of lizards and snakes

- Loosely jointed upper jaw and paired reproductive organs in males

- Structurally diverse Lizards- presence of limbs - Common lizards- iguanas,

chameleons, skinks and geckos  -  Live everywhere except

Antarctic - Special adaptations- agility and

camouflage - 2 species are venomous- Gila

monster (SW U.S.) and beaded lizard (western Mexico)

- Most prey on insects or small animals

- Blend with background - chameleons- remain

inconspicuous and fend off enemies

- Horned lizards- spiked armor, when disturbed they inflate themselves, gape, hiss and squirt blood from eyes

- Skinks and geckos- lose their tails and regenerate- autotomy- escape from predators

- Most lizards are small- .3m in length; iguanas- 1m in length

- Largest lizards- monitors- Komodo dragon (Indonesia) 3m

- Consume prey whole and use tail as defense weapon

Order Sphenodontida (Rhynchocephalia) - tuatara

• 2 spp. - max. length c.600mm.• most primitive living reptile, unchanged for 200my,

relatives extinct 60 mya.• primitive features: pineal eye structure, foramen

(openings) in skull, teeth fused to jawbone, no ear opening.

• temperature-dependent sex determination in incubating eggs.

• caudal autotomy - lose tail voluntarily; fracture planes within vertebra; tail regrowth.

• formerly widespread, now restricted to c.30 offshore islands.

NZ reptile fauna

Sphenadon punctatus

Order Squamata - lizards & snakes

Lizards: • at least 80 lizards species and subspecies of lizard known in New Zealand (still being discovered and described).

• caudal autotomy.• lizards represented by geckos and skinks in

New Zealand

Robb 1980

Robb 1980

Geckos

- flattened body with short legs- granular scales, transparent scale over eye- eyelid non-moveable, cleaned by the tongue- able to climb vertical surfaces - specially adapted

gripping bristles (lamellae) underneath toes- can make noises - chattering sound when disturbed

or threatened- most southern geckos in the world, largest species

(kawekaweau, extinct)- NZ species retain eggs in body to give birth to live

young (ovoviviparity

2 NZ genera- Hoplodactylus – 9 spp. (1 extinct), brown, limited colour

change, nocturnal- Naultinus – 7 spp., green, diurnal

Skinks

- elongated body, rounded in cross-section, long tapering tail.

- very agile.- flat, shiny, overlapping scales.- moveable eyelids (blink).- most ovoviviparous.

2 NZ genera- Cyclodina – 6 spp. (1 extinct), diurnal.- Oligosoma (Leiolopisma) – 21 spp. (1 extinct),

nocturnal or crepuscular.- [1 introduced sp. – rainbow skink, northern Nth Is.]

Other reptiles?

- turtles- snakes- crocodiles

Evolution of Reptiles

TRANSITION FOSSILS show that there was a slow and steady evolution from amphibians to reptiles.

Age of the Large ReptilesAge of the Large Reptiles

Approximately Approximately 195 million years 195 million years ago, the mammal-ago, the mammal-like reptiles that like reptiles that populated the populated the world disappeared world disappeared and were replaced and were replaced by the dinosaursby the dinosaurs

Mass Extinction – 65myaMass Extinction – 65mya

Scientists not sure Scientists not sure why the dinosaurs why the dinosaurs disappeared disappeared

Possibly the world Possibly the world was hit by a meteor was hit by a meteor

Only relatively Only relatively small reptiles were small reptiles were left behindleft behind

Major radiation into all ways of life; terrestrial, aquatic, aerial.

Ichthyosaurs: fully aquatic, but air breathing. A reptile equivalent to whales or porpoises. Mostly fish eating.

Pterosaurs = hang glider wings.

Archosaurs = major dinosaur groups

Plus crocodiles, and bird ancestry.

A very diverse and complex group. - die out at Cretaceous boundary = meteor?