Transcript Chapter 20 Reptiles

Chapter 20
Reptiles
Introduction
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Class Reptilia
Order Testudines or Chelonia -----Turtles
Order Rhynchocephalia------------Tuataras
Order Squamata------------------snakes, lizards,
worm lizards
• Order Crocodilia-------------------crocodiles,
alligators, caimans, gavials.
Evolutionary 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 Egg
Basic Characteristics of the Reptile
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 chicken
Compare and Contrast
Order Testudines (Chelonia)
Turtles
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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)
Turtles
• 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 Rhynchocephalia
Lizardlike 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 25
Order Squamata
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Broken down into:
Suborder Sauria – THE LIZARDS
Suborder Serpentes- THE SNAKES
Suborder Amphisbaenia- WORM
LIZARDS
Suborder Sauria – THE
LIZARDS
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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 Snakes
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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
Lizards
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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 Crocodilia
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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
Alligator
70-80 white, pointed
teeth of similar shape
Alligator
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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.
Crocodiles
Crocodiles
• 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.
Crocodiles
• 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 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.
Locomotion
• 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.
Locomotion
• 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.
Locomotion
• 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 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 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 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 Functions
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.
Nervous and Sensory Functions
of Reptiles
Nervous and Sensory Functions
of Reptiles
• 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.
Nervous and Sensory Functions
of Reptiles
• 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 Organs
Nervous and Sensory Functions
of Reptiles
• 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.
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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.
Reproduction
• 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.
Reproduction
• 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.
Reproduction
• 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
Reproduction
• 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.
Reproduction
• 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.
Reproduction
• 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.