Reptiles by jennyyingdi


  Bio II
Origin and Evolution
 300 million years ago
 One of the largest and most successful
  terrestrial vertebrates
History of Reptiles
 Comparative anatomy studies show
  development from amphibians
 Oldest known fossils are from the
  Carboniferous period—350 million years
 Small, four-legged, with teeth adapted to
  eating insects
 Abundance of insects at this point in
  history may be reason they flourished
The Age of Reptiles
                     Rapid diversification
                     Dominant land
                      vertebrate by the
                      Permian Period
                     Mesozoic Period was
                      the Age of the Reptiles
The Age of the Reptiles--Dinosaurs
   Some as large as           Fossils on all
    Brachiosaurus               continents including
       23m long                Antarctica
       12 m tall              Aquatic success
       77,000kg                   Ichthyosaurs
   Some were the size of          Plesiosaurs
    chickens                   Aerial success
   300 genera identified          Pterosaurs
    to date
Ichthyosaur, Plesiosaur, and Pterosaur
Extinction of Dinosaurs
   When: end of the                Hypothesis details
    Cretaceous period 65mya             Asteroid impact caused
   Hypothesis #1: Asteroid-             large dust clouds
    Impact Hypothesis                   Dust blocked out the sun
       Developed by Physicist           causing major climactic
        Luis Alvarez and his             shifts and extinction
        geologist son Walter        Evidence
        Alvarez                         Iridium in Cretaceous
       Presented in 1980                layer of Earth’s crust
                                        Iridium typically rare, but
                                         common in asteroids
                                        Impact crater on the
                                         Yucatan Peninsula—180km
Extinction of Dinosaurs continued
Extinction of the Dinosaurs continued
   Hypothesis #2: Volcano Eruption Hypothesis
       Caused by the breakup of Pangaea
       Massive volcanic activity spewed dust into the atmosphere
   Hypothesis Details
       Iridium locked deep within the Earth was brought to the
        surface by the eruptions
Why is it called the K-T Extinction?
                      K is from the Greek
                       word “kreta” meaning
                      Geologically, the
                       Cretaceous Period is
                       characterized by a
                       chalk layer in the
                       Earth’s crust
                      T is for Tertiary
                       Period, which follows
                       the Cretaceous
Success of Reptiles
   Representatives of modern day reptiles
    must have survived the K-T extinction
       Turtles and Tortoises
       Snakes and Lizards
       Tuataras
       Crocodilians
 Approximately 6000 species alive today
 Found on all continents except Antarctica
Reptile Phylogeny
The Amniotic Egg
 Reptiles are considered the first fully
  terrestrial vertebrates due to evolution of
  the amniotic egg
 Water is no longer needed to reproduce
 Self-contained aquatic environment—they
  brought the pond with them
The Amniotic Egg continued—
   Amnion                            Allantois
       Thin membrane                     Stores nitrogenous
       Encloses the fluid the             wastes of the embryo
        embryo floats in                  Rich blood supply
   Yolk sac                              Serves as a lung in gas
       Enclose the yolk
       Provides a fat-rich food      Chorion
        supply                            Surrounds all the other
                                          Protects the embryo
The Amniotic Egg continued—Other
Important Notes
 Albumin contains protein and water
  needed by the embryo, aka, the white
 Protective shell
 Shows common ancestry of reptiles, birds,
  and mammals
Water-tight skin
   Thick, dry, scaly skin
    to prevent desiccation
   Can not exchange
    gases through the
   Keratinized
   Lipids and proteins
    also present
   Aids in protection
    from infection and
Respiration and Excretion
   Respiration                     Excretion
       Internalized lungs              Uric acid
        maintains moisture and          Less toxic than urea
        allows efficient gas             and ammonia
        exchange                        Requires little dilution
                                        Water conservation
Characteristics of Reptiles—Circulation
 Higher blood pressure than amphibians
 Two loop system
       Pulmonary carries deoxygenated blood from
        heart to lungs and returns oxygenated blood
       Systemic carries oxygenated blood to body
        and return deoxygenated blood
Characteristics of Reptiles—Circulation
Characteristics of Reptiles—Circulation
   Lizards, Snakes, Tuataras,        Crocodilian Heart Structure
    and Turtles Heart Structure           Two atria
       Two atria                         Two separate ventricles
       One ventricle                     Sinus venosus and conus
       Dividing membrane called           arteriosus as found in fish,
        the septum                         but smaller
                                          Sinus venosus can be
                                           absent in some species
                                          Sinus venosus function—
                                           collect blood from body
                                           and channel to right atria
                                          Conus arteriosus
                                           function—forms the base
                                           of three large arteries
                                           exiting the heart
Characteristics of Reptiles—Circulation

   Pulmonary artery constriction
       Redirects oxygenated blood back to body instead of to
       Bypassing lungs allows for greater thermoregulation
       Birds and mammals do not have this circulatory
Characteristics of Reptiles—Respiration
                       Large lungs divided
                        into several chambers
                       Alveoli for gas
                       Snakes typically only
                        use their right lung—
                        left is deflated or
                        completely absent
                       Fill lungs by
                        expanding rib cage
                        similar to us—creates
                        negative pressure
Characteristics of Reptiles—Nervous
                       Brain is similar in size
                        to an amphibian of
                        similar size
                       Greater complexity
                        than amphibian
                       Larger cerebrum—
                        control and integration
                        of behavior
                       Large optic lobes—
                        good vision
Characteristics of Reptiles—Nervous
System continued
   Tympanum and
   Snakes lack the
       Detect sound via
       Sounds transmit to the
        columella through the
Characteristics of Reptiles—Nervous
System continued
   Jacobson’s organ
       Specialized sense organ
        located in the roof of
        the mouth
       Sensitive to smell
       Forked tongue gathers
        odors and transmits to
       Not present in
        crocodiles and most
Characteristics of Reptiles—Nervous
System continued
                       Pit vipers
                           Heat sensitive organs or
                            pits on head
                           Pits are located below
                            each eye
                           Used to determine
                            direction and distance
                            to prey
Characteristics of Reptiles—
   Control of body                          Active ectotherms maintain
    temperature                               body temperature close to
   Two main types                            endotherms
       Ectothermy                           Basking behaviors to warm
            Environment warms body           body
            Reptiles, fish, amphibians      Advantages and limitations
            Slow metabolism                     Slow metabolism requires
       Endothermy                                little food
            Generate own heat                   Not capable of inhabiting
            Rapid metabolism                     cold environments
            Hair, feathers, and fat as          Speed only in short bursts
Characteristics of Reptiles—
Reproduction and Parental Care
   Copulatory organ                       Viviparous
    permitting internal                        Only a few species of
    fertilization                               lizard and snake use
   Oviparous                                   placental method
       Characteristic of most             Parental care
        reptiles                               Most offer no care
   Ovoviviparous                              Some lizards and snakes
       May lay shortly before                  guard eggs until hatching
        hatching or retain till birth          Crocodilians offer most
       Water and oxygen from                       Nest building and
        female, food from yolk
                                                    Carry newborns to water
                                                    Protection up to a year
Characteristics of Reptiles—Reproduction
and Parental Care continued
Modern Reptiles
Common Characteristics of Modern
 Amniotic egg
 Internal fertilization
 Dry, scaly skin—crocodilians possess
 Respiration through lungs
 Ectotherm metabolism
Order Chelonia
                    Approximately 250
                    Turtles—aquatic
                    Tortoises—terrestrial
                    Oldest fossils are
                     more than 200 million
                     years old
                    Very little evolutionary
                     change due to
                     excellent design of
Order Chelonia—Shell characteristics
   Shell inhibits              Plastron is the bottom
    expansion of rib cage       Movable plastron on
    and breathing—               box turtles
    abdominal, pectoral,        Vertebrae are typically
    and shoulder muscles         fused to carapace
    control inhalation and
    exhalation                  Pelvic and pectoral
                                 girdles are inside of
   Made of fused bony           ribs—limits mobility
   Carapace is the top
Order Chelonia--Characteristics
   Beak instead of teeth
   Habitats reflect shell
    and limb design
       Aquatic—streamlined,
        disk-shaped shell and
        webbed feet
       Terrestrial—domed shell
        for retraction and
        sturdy, scaled limbs
       Marine—flippers as
Order Chelonia--Reproduction
                    Dig holes with hind
                     limbs and lay eggs
                    No care for young
                    Marine turtle
                     may travel 2000km to
                     their birth beach
Order Crocodilia
   Most closely related to
   21 species
   Large, heavy-bodied,
    aquatic reptiles
   Thecodonts—teeth are
    set in sockets
   Crocodiles, alligators,
    caiman, and gavial
Order Crocodilia
   Crocodiles are subtropical      All are carnivorous ambush
    and tropical dwellers            hunters
   Alligators are found in         Can see while underwater
    China and the Southern          Can breathe when slightly
    U.S.                             submerged due to nostrils
   Caimans are found in             high on rostrum
    Central and South America       Valve at the back of throat
    and have been introduced         prevents water from
    to Florida                       entering the lungs while
   Gavial are native to             eating underwater
    Northern India
Order Squamata
 5500 species of lizard and snake
 Upper jaw is loosely attached to skull—
  kinetic skull
 Most structurally diverse
Order Squamata--Lizards
   3000 species
   Every continent
    except Antarctica
   Prey on insects and
    small animals
   Larger species, Desert
    Iguana and
    Chuckwalla, feed on
   Komodo dragon feeds
    on goats and deer
Order Squamata—Lizards continued
                   Two Venomous lizards
                       Gila Monster
                       Beaded Lizard
Order Squamata—Lizards continued
   Agility, speed, and
    camouflage to avoid
   Autotomy—ability to
    detach tail
   Most are less than
    30cm in length
   Largest are the
       Family Varanidae
       Forked tongues
Order Squamata—Snakes
                  2500 species
                  Lack legs—possibly
                   evolved due to
                   movement through
                   thick grasses where
                   legs were a
Order Squamata—Snakes continued
 Unique anatomy allows movement
 100 to 400 vertebrae
 Ribs attached to each vertebra
 Thousands of muscles attached to
 Muscles manipulate skin and skeleton
  allowing movement
 Belly scales or scutes proved traction
Order Squamata—Snakes continued
Order Squamata—Snakes continued
   Prey capture and                     Injection of venom
    consumption                               Three methods
                                                 Fangs in back—
   Two methods                                   boomslangs and twig
       Constriction
                                                 Fixed front fangs—
            Wrap bodies around                   elapids—cobras,
             prey and increase coil               craits, and coral
             tension until                        snakes
             suffocation                         Movable front fangs—
            Boas, pythons,                       vipers—rattlesnakes,
             anacondas, king                      copperheads, water
             snakes, gopher snakes,               moccasins
             rat snakes
Order Squamata—Snakes continued
   Venom types
       Neurotoxic—affects optic nerve and diaphragm
       Hemotoxic—breaks down red blood corpuscles
        and causes hemorrhaging
       Combination
Order Squamata—Snakes continued
Order Squamata—Snakes continued
Order Squamata—Snakes continued
Order Squamata—Snakes continued
Order Squamata—Snakes continued
 Teeth not designed for chewing
 Swallow prey whole
 Upper and Lower jaws move
  independently to allow large prey items
 Mouth can open about 130 degrees
 Extremely flexible lower jaw
Order Rhynchocephalia
   Ancient form of reptile
   Two living species—the tuataras of genus
   Only found on the two small islands of New
   Tuatara means “spiny crest”
   Grow to about 2 feet in length
   Burrowers during the day
   Feed on insects, worms, and small animals at
   Introduced species have caused their numbers to

To top