chapter 20 reptiles

Chapter 20Chapter 20ReptilesReptiles

IntroductionIntroduction

• Class Reptilia• Order Testudines or Chelonia -----Turtles• Order Rhynchocephalia------------Tuataras• Order Squamata------------------snakes, lizards,

worm lizards• Order Crocodilia-------------------crocodiles,

alligators, caimans, gavials.

Evolutionary PerspectiveEvolutionary Perspective

• I. It is believed that the earliest members of the reptile family were the first to have amniotic eggs.

• A. Characteristics of amniotic eggs:• 1.Extraembronic membranes (protect the embryo

from desiccation).• 2. cushion the embryo• 3. promote gas transfer• 4. store waste materials• 5. leathery or hard shells• 6. albumen cushions the embryo and provides

moisture and nutrients• 7. yolk supplies food

Amniotic EggAmniotic Egg

Basic Characteristics of the Basic Characteristics of the Reptile GroupReptile Group

• 1. They have a skull with 1 surface for movement with the first neck vertebra

• 2. respiration by lungs• 3. kidneys• 4. internal fertilization• 5. amniotic eggs• 6. dry skin with keratinized epidermal scales*****note there are 17 orders of reptiles, most

extinct, 4 orders today.********

NO not a chickenNO not a chicken

Compare and ContrastCompare and Contrast

Order Testudines (Chelonia)Order Testudines (Chelonia)TurtlesTurtles

• Roughly 225 species of turtles• Characteristics• 1.bony shell• 2. limbs articulating internally to the ribs• 3. keratinized beak rather than teeth• 4. hinge that allows the shell to open and

close (head and legs to come in and out)• 5. 8 cervical vertebrae (which can curve into

S shape which allows turtles head to be drawn in)

Order Testudines (Chelonia)Order Testudines (Chelonia)TurtlesTurtles

• 6. long life spans• (reach sexual maturity at 7-8 years, and live

14 years or more, some on the Galapagos Islands may live in excess of 100 years)

• 7. oviparous (eggs are deposited outside the body)

• Females use hind limbs to excavate nests in the soil. They lay eggs there and cover with soil. Usually laid in clutches of 5-100 eggs.

Order RhynchocephaliaOrder RhynchocephaliaLizardlike ReptilesLizardlike Reptiles

• Characteristics• 1. two rows of teeth on the upper jaw, and a single

row on the lower jaw• ****gives them a bite that could decapitate a small

bird*****• 2. widely distributed in New Zealand• 3. often fall prey to human influences and domestic

animals• 4. oviparous (lay eggs outside the body)• 5. share underground burrows with seabirds• 6. venture out of their burrows at dusk and dawn to

feed on insects or occasionally small vertebrates.• See picture on page 316, Figure 20.7

Stopped here on feb 25Stopped here on feb 25

Order SquamataOrder Squamata

• Broken down into:• Suborder Sauria – THE LIZARDS• Suborder Serpentes- THE SNAKES• Suborder Amphisbaenia- WORM

LIZARDS

Suborder Sauria – THE Suborder Sauria – THE LIZARDSLIZARDS

• Characteristics• 1. 3,300 species• 2. two pairs of legs• 3. upper and lower jaws unite anteriorly• 4. length varies from 1 centimeter to 3 meters• 5. live on surface substrates• 6. hide or live under rocks or logs• 7. some burrow or stay in trees• 8. deposit eggs under rocks or debris or in burrows• 9. can be oviparous, ovoviviparous, viviparous• Examples: Geckos, Iguanas, Gila Monster – the only

venomous lizards known.

Suborder Serpentes- The Suborder Serpentes- The SnakesSnakes

• Characteristics:• 1. 2,300 species of snakes• 2. 300 species are venomous• 3. Worldwide about 30-40,000 people die from snake bites,

most of these are in Southeast Asia• 4. elongated• 5. lack limbs• 6. may have more than 200 vertebrae and pairs of ribs• 7. upper jaws are movable, loosely connected to lower jaw• 8. Narrowing of the body has resulted in: loss of left lung,

displacement of gallbladder, the right kidney, and often the gonads.

• 9. Most snakes are oviparous• 10. However the New World boas, garter snakes give birth to

live young.

Suborder Amphisbaenia- Worm Suborder Amphisbaenia- Worm LizardsLizards

• Characteristics:• 1. 135 species• 2. specialized burrowers of soil in Africa• 3. most are legless• 4. skulls are wedge or shovel shaped• 5. single median tooth in the upper jaw• 6. skin has ring like folds• 7. feed on worms and small insects• 8. oviparous

Order CrocodiliaOrder Crocodilia

• Characteristics:• 1. 21 species• 2. triangular eye openings for the eye openings• 3. laterally compressed teeth• 4. elongated snout• 5. nostrils are at the tip of the snout• 6. muscular, elongated tail that is laterally compressed tail for

swimming• 7. food is swallowed whole• 8. the stomach is like a gizard, they swallow rocks and other

objects to be used in breaking apart food and digestion• 9. oviparous, lay eggs outside body and build nests

AlligatorAlligator70-80 white, pointed teeth of similar shape

AlligatorAlligator

• Length in wild• 8-9" at birth • typical old male 15', female about 10' • largest recorded in Florida -- 17'5" • Weight in wild• varies among alligators and is not related to length • largest males can weigh up to 1,000 pounds • Body• adults black • young have vertical yellow bands until about 3-4 years old

(see photo below in "Young") • Famous for the death roll. Grab the prey go down into the

water and spin until the prey drowns.

CrocodilesCrocodiles


• Size greatly varies between species, from the dwarf crocodile to the saltwater crocodile. Species of Palaeosuchus and Osteolaemus grow to an adult size of just 1 metre (3.3 ft) to 1.5 metres (4.9 ft). Larger species can reach over 4.85 metres (15.9 ft) long and weigh well over 1,200 kilograms (2,600 lb). Crocodilians show pronounced sexual dimorphism with males growing much larger and more rapidly than females.


• Ambush Hunters: Crocodiles are ambush hunters, waiting for fish or land animals to come close, then rushing out to attack. As cold-blooded predators, they can survive long periods without food, and rarely need to actively go hunting. Known for having lock jaw. Escape rarely happens.

• World's Largest Reptile: The largest species of crocodile, also Earth's largest reptile, is the Saltwater Crocodile, found in northern Australia and throughout South-east Asia.

Crocodile productsCrocodile products

• Crocodile leather wallets from Bangkok Crocodile Farm• Crocodile leather can be made into goods such as wallets,

briefcases, purses, handbags, belts, hats, and shoes.• Crocodile meat is consumed in some countries, such as

Australia, Ethiopia, Thailand, South Africa and also Cuba (in pickled form); it can also be found in specialty restaurants in some parts of the United States. The meat is white and its nutritional composition compares favourably with that of other meats. It tends to have a slightly higher cholesterol level than other meats. Crocodile meat has a delicate flavour; some describe it as a cross between chicken and crab. Cuts of meat include backstrap and tail fillet.

LocomotionLocomotion

• Unlike amphibians the reptile family can not breath through their skin. Their skin serves no respiratory function.

• Characteristics of Reptile Skin:• Dry• Thick• Keratinized (hardened scales)• Snakes use their scales to provide contact with

substrates (trees, grass, dirt) and create movement.


• The periodic shedding of skin is called ecdysis. And happens periodically. It usually starts at the head and then moves down the body. Some shed complete skins and others flake off in pieces.

• When a snake is going through this it is called opec cycle. And the snake will have a blue hue to it.

• The epidermis is the outer layer and it has no blood vessels and very few chromatophors or color pigments.


• Most Reptiles walk on legs, others slither on the ground. • Reptiles have a lot of mobility in their neck region. The

atlas and axis are the upper cervical vertebra in the neck. • The ribs are closely associated with the leg or belly

movements. Muscle concentration is high here. • In order to escape predators some lizards can go through

autotomy, loose their tail to get away and grow a new one. • Prehistoric reptiles walked on their back two legs and this

is called being bipedal.• Most reptiles today walk on all four legs. Knee and elbow

joints rotate posteriorly in most.

Nutrition and DigestionNutrition and Digestion

• Most Reptiles are Carnivores (eat meat)• One exception are turtles who will eat just about anything.• Some reptiles have a sticky tongue to help catch prey,

and the length of the tongue can be longer than the body of the reptile.

• Jaws of reptiles are loosely attached and often can be unhinged to allow them to eat large prey. The upper jaw is called the maxillary and the lower the mandible. Fangs are usually associated with the maxillary bone.

• Inside the mouth of the snake they have a glottis which is a respiratory opening that allows them to breath while eating.

Nutrition and DigestionNutrition and Digestion

• Some fangs are always in a straight or vertical position. Others can be folded up and then unfolded when needed.

• Venom glands used to kill prey are actually modified sweat glands. That venom is moved through the fang into the prey.

• Most of these cocktails contain neurotoxins (attacking the prey’s nervous system) or Hemotoxins (which break up blood cells and cause the victim to suffocate to death from the lack of oxygen to the body cells.

Body TemperatureBody Temperature

• Reptiles are cold blooded.• Reptiles and amphibians are very similar in this

area.• Reptiles have a higher blood pressure because

blood must be pumped at high speeds to reach all parts of the body.

• Reptiles use their environment to help regulate their temperature.

• The lack of breathing is called apnea. Turtles can not breath when they go into their shells.

Nervous and Sensory Nervous and Sensory Functions of ReptilesFunctions of Reptiles

• The reptiles cerebral hemisphere (a large portion of the brain) is larger than that of the amphibian. The increased size is believed to be associated with the sense of smell capabilities of the reptile.

• Also the optic lobes (found in between the cerebrum and the cerebellum) and cerebellum (found behind the cerebrum) are enlarged. This helps with vision and greater coordination of muscle functions.


• Vision is the dominant sense in most reptiles.• Some reptiles have an additional eye in the roof

of the forebrain. Page 403. This is called a median (parietal) eye. It is covered with skin and is not known to be able to form any images. It does help with the detection of light and dark periods.

• Ears-• Detect vibrations• Lack a middle ear cavity, auditory tube, tympanic

membrane.


• The jaw works with (articulates) with the stapes in the ear and receives Substrate vibrations (vibrations from physical objects, ground, etc).

• Snakes can also detect air vibrations.Taste• Jacobson’s organs (vomeronasal)- are pouhces that

open through the palate of the reptile. Turtles do not have these. Baby crocodiles have this but adults do not. Snakes and lizards have these and they work with their forked tongues to sample chemicals in the air.

Jacobson’s OrgansJacobson’s Organs


• Pit organs• Rattlesnakes and other vipers have these

heat sensitive organs. They are located on each side fo the face between the eye and nostril.

• They are used to detect temperature. Mostly they are used to detect warm blooded prey at night.

• Anatomy of a snake. • 1 esophagus, • 2 trachea, • 3 tracheal lungs, • 4 rudimentary left lung, • 5 right lung, • 6 heart, • 7 liver, • 8 stomach, • 9 air sac, • 10 gallbladder, • 11 pancreas, • 12 spleen, • 13 intestine, • 14 testicles, • 15 kidneys.

ReproductionReproduction

• Structures- • Gonads are the male reproductive

structures that are ducts designed to conduct sperm to the cloaca.

• Seminal receptacle- is a storage area in the female that allows the female to store sperm until they are used. This area will nourish the sperm. In some sperm is stored for 4-6 years before being used.


• Copulation- is the scientific word for mating.• Fertilization- is when a sperm and egg unite to

form a zygote• Courtship- any behavior that attracts a mate.

They use body language, sound, color, sight, smell.

• Tactile stimulation- the use of tail waving to attract or acquire a mate.

• Sex pheromones- smells used to tell if the opposite sex is ready to mate.


• Vocalizations- sounds used during mating season to attract a mate, or warn off predators.

• Nest- any area built by the reptile for the purpose of rearing young. Most reptile nests are on the ground and made of dirt and sticks.

• Parhenogenesis- is a form of asexual reproduction found in females, where growth and development of embryos occurs without fertilization by a male


• Snake: 2 - 3 months, live birth and eggs, internal fertilization

• Alligator-Offspring• Alligator females will typically build a nest near water where

she will deposit 30-50 eggs. She will bury the nest with vegetation and mud which raise 2-3 feet above ground level. She will guard the nest through the 60-day gestation period and aid the hatchlings with breaking out of the nest. Hatchlings will form social groups called "pods" and remain with the mother for up to a year after birth.


• Crocodiles-• This species digs hole nests up to 50cm deep in

sandy banks, several metres from the water. These may be in close proximity to other nests. Timing of nesting behaviour varies with geographic location - it takes place during the dry season in the north, but at the start of the rainy season further south, usually from November through to the end of December. Females reach sexual maturity around 2.6 m, males at around 3.1 m. Females lay around 40 to 60 eggs in the nest, although this number is quite variable between different populations. Females remain near the nest at all times.


• Incubation time averages 80 to 90 days (ranges from 70 to 100 days), after which females open the nest and carry the juveniles to the water. Both males and females have been reported to assist hatching by gently cracking open eggs between their tongue and upper palate. Hatchlings remain close to the juveniles for up to two years after hatching, often forming a creche with other females. As with many crocodilians, older juveniles tend to stay away from older, more territorial animals.

chapter 20 reptiles

Documents

oviparous eggs

deposit eggs

oviparous lay eggs

upper jaws

lower jaws

lizardssuborder serpentes

orders of reptiles

amniotic eggs6