Reptiles

Objectives: Objective 1: Describe the characteristics of Modern Amphibians Objective 2: Describe characteristics of the following orders: (Apoda, Urodela, Anura) Objective 3: Explain the origins and evolutionary process of modern amphibians Objective 4: Describe the characteristics of modern Reptiles Objective 5: Describe characteristics of the following orders: (Squamata, Sphenodonta, Crocodilia, Testudines) Objective 6: Explain the characteristics of respiration, feeding, and reproductive strategies for reptiles Objective 7: Identify the amphibians and reptiles in Idaho and the families they are associated with Objective 8: Student Presentation of Amphibians and Reptiles.

# of Species of Reptiles Species Numbers by Higher Taxa: Amphisbaenia (amphisbaenians) 165 Sauria (lizards) 4765 Serpentes (snakes) 2978 Testudines (turtles) 307 Crocodylia (crocodiles) 23 Rhynchocephalia (tuataras) 2 Reptiles total 8240

Characteristics of a Reptile Vertebrate animals Lungs Scaly skin Amniotic egg 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 were developed for life away from water Scaly skin provided protection against the elements and desiccation The amniotic egg protected 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 one that fits their bodies)

Reptile Lungs Respiration is no longer through the skin, but only through internally protected and moistened lungs. They have a much greater surface area for the exchange of gases. They are inflated and deflated by the expansion & contraction of the rib cage.

Scaly Skin An adaptation to life out of water Waterproof Dry, leathery Protective scales Must be molted

Amniotic Egg – Reptiles and Birds Compared to the development of seeds in plant evolution Reptile eggs have leather shell Has several membranes Contains yolk rich in nutrients for embryo Mammals have comparable modified membranes

The Amniotic Egg – adaptation to life on land Amphibians were not able to move away from the water because their eggs would desiccate Reptiles eggs prevent desiccation

Reptile Legs Short tetrapods for walking Positioning of the legs more directly under the animal. This position provided more support than the splayed arrangement of the Amphibian legs.

Paired Limbs The paired limbs usually have five toes and are variously adapted for: Swimming Running Climbing (Absent altogether in the snakes)

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

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

Mass Extinction – 65mya Scientists not sure why the dinosaurs disappeared Possibly the world was hit by a meteor Only relatively small reptiles were left behind

Reptile Feeding Ex. 1: Iguana Herbivores – tear plants using teeth and jaws Have long digestive systems

Carnivores Snakes – have extendible jaws to swallow their prey hole.

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 spit out the shell!

Carnivores The king cobra eats other snakes

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 .

Reptilian Respiratory System Reptilian lungs are better developed than amphibians Muscular ribs help them expand the chest cavity as we do to draw in the air Nostrils allow them to bring in air while their mouth is closed Snakes only have one long, lung that fits in their bodies. Snakes also have a tube that projects out of the mouth when the snake is swallowing so that it can breathe and swallow at the same time

Breathing Tube

Internal Transport Double-loop system Most reptiles have a 3 ½ chambered heart (ventricle has a partial septum) Crocodiles and Alligators have a 4 chambered heart like ours.

Reptiles need a more efficient system for delivering oxygen since they have dry skin.

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

Nervous Systems Frog Brain Alligator Brain Larger cerebrum/ cerebellum than the amphibians Daytime reptiles have good color vision: turtles can see color better than humans

Excellent Sense of Smell - Snakes Have pair of nostrils Also have special organs (vomeronasal organs) on roof of mouth Tongue picks up chemicals and brings them to the vomeronasal organs to “taste” the 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

Jacobson’s Organ

Pit vipers

Movement Muscle and skeletal systems are more advanced than amphibians

Snakes - movement Snakes press their ventral scales against the ground Muscles around the ribs expand and contract in waves causing the s-shaped movement

Gecko – suction cup toes Geckos have special flaps of skin on its toes – creating very sticky appendages

Reptile Reproduction Most have internal fertilization Penis delivers sperm into cloaca of female

Reptile Reproduction Internal fertilization Male inserts penis into female’s cloaca Female’s body coats the embryos in protective shell, with membranes and yolk sac

Reptile Reproduction Most reptiles are oviparous Some provide minimal care

Amniotic Egg

Amniotic Egg Structures & Functions Chorion provides a special hard covering that is permeable to respiratory gases (O2 and CO2) while being impermeable to water vapor. Allantois is a storage reservoir for metabolic waste products such as nitrogenous compounds. Amnion is a fluid filled sac that acts as a cushion for the embryo and also prevents desiccation. Yolk sac contains food for the embryo, thus eliminating the need for a larval stage.

The temperature inside the nest of several crocodilian species decides the sex of the young. ~50-80 eggs If the nest temperature is 30ºC, females will hatch from all the eggs If the temperature is above 34ºC, all will be males. If the temperature is in between, there will be young of both sexes.

Orders to know: Objective 5 Order Squamata: Snakes, Lizards, and amphisbaenians. Skin of horny epidermal scales or plates, which is shed; quadrate movable; skull kinetic (except amphisbaeinians); vertebrae usually concave in front; paired copulatory organs. There are three suborders Lacertilia (lizards), Amphisbaenia (worm lizards), and Serpentes (snakes). Order Sphenodonta: Tuataras. Primitive diapsid skull; vertebrae biconcave; quadrate immovable; parietal eye present; two extant species in Spenodon. Order Crocodilia: Crocodiles and Alligators. Skull elongate and massive; nares terminal; secondary palate present; four-chambered heart; vertebrate usually concave in front; forelimbs usually of five digits; hind limbs of four digits; quadrate immovable; advanced social behavior; 23 species. Crocodiles and alligators can be distinguished on the basis of head morphology. Crocodiles have a relatively narrow snout and when their mouths are closed, the fourth lower jaw tooth is visible. Alligators generally have a broader snout and their fourth lower jaw tooth is hidden by fitting into a notch in the upper jaw. Order Testudines: Turtles; Body in a bony case of dorsal carapace and ventral plastron; jaws with keratinized beaks instead of teeth; vertebrae and ribs fused to overlying carapace; tongue not extensible; neck usually retractable; approximately 300 species.

Tuataras Resembles small version of reptiles from the dinosaur age Only found on small islands off N. Zealand Has pineal gland on top of skull detects light – actually determines changes in length of day

Lizards – chameleons

Lizards – Gila Monsters - venomous

Hatchling Komodo Dragon

Monitor Lizards – may be like dinosaurs were. Largest is the Komodo dragon

Family Amphisbaenidae (Worm Lizards) Size: The total body length ranges from 10 cm to about 70 cm. Distribution: Mostly Africa & South America with a few species in Europe and North America. Habitat: Soil. Reproduction: usually oviparous, but some are live-bearing

Ectothermy – “heat from outside” Usually have relatively low resting metabolic rates Therfore, they do not generate much body heat Body temp. is actually higher than the surroundings These animals remain active for short periods of time, then have rests in between activity

Endothermy – “heat from inside” These animals have relatively high metabolic rates They use this heat to keep their bodies warm Usually have a lower internal temp. than the surroundings Endotherms can remain active for longer periods of time These animals have greater energy needs – need to eat more food than ectoderms

Snake Anatomy

Turtle Anatomy

Turtle Shell Anatomy

Turtle Shell Anatomy

Fusion of ribs, vertebrae, & carapace