Transcript Modern Amphibians

Modern Amphibians
• Part two
Modern Amphibians:
Order Caudata
• Includes salamanders
(may also be called
newts).
• Members may be fully
aquatic, fully
terrestrial, or
amphibious.
• Many reproduce in
water. Some
reproduce on land,
with no swimming
larval stage.
Modern Amphibians:
Order Caudata
• Larvae and adults
are carnivorous.
• Some have no
lungs, and respire
through their skin
only.
Modern Amphibians:
Order Gymnophiona
• Includes caecilians (legless amphibians
that resemble small snakes).
• Most are burrowing. They have small
eyes beneath skin or bone, and are often
blind.
Modern Amphibians:
Order Gymnophiona
• All are carnivorous.
• All are thought to have internal fertilization.
• Some lay eggs which the female guards,
others develop inside the female.
Phylogenetic Diagram of
Amphibians
Characteristics of Amphibians:
Skin
Amphibian skin serves two important functions:
• Respiration - The skin is permeable to gases
and water. Mucous glands secrete a lubricant
that keeps the skin moist in air.
• Protection - The skin protects amphibians from
infection and secretes a foul-tasting or
poisonous mucus that protects amphibians from
predators.
Characteristics of Amphibians:
Skeleton
A strong skeleton supports the body of amphibians against
the force of gravity.
• Vertebrae interlock to form a strong, rigid structure.
• Strong limbs assist with standing and walking.
• Pectoral and pelvic girdles transfer weight to the limbs.
• Skeletons of frogs are specialized for jumping and
landing.
Characteristics of Amphibians:
Skeleton
• Fused bones add strength
to the forelimbs and hind
limbs.
• Thick arm bones and
pectoral girdle absorb
shock of landing.
• Long hind legs allow frogs
to jump farther.
• Lengthened pelvic girdle
and fused vertebrae add
support.
Characteristics of Amphibians:
Circulatory System
The circulatory system is divided into
two loops.
• Pulmonary circulation - carries
deoxygenated blood from the heart to
the lungs and back to the heart.
• Systemic circulation - carries
oxygenated blood from the heart to the
body and back to the heart.
Amphibian Heart Structure
Amphibians use positive
pressure breathing
Amphibian Lung Structure
Characteristics of Amphibians:
Digestive System
• Includes the pharynx, esophagus,
stomach, liver, gallbladder, small intestine,
large intestine, and cloaca.
• The upper part of the small intestine is
called the duodenum.
• The coiled middle portion of the small
intestine is the ileum.
Characteristics of Amphibians:
Digestive System
• A membrane that holds the small intestine
in place is called the mesentery.
• Waste materials are stored in the cloaca
and exit the body through the vent.
Characteristics of Amphibians:
Digestive System
Accessory Glands
• The liver produces bile, which is stored in
the gallbladder and helps break down fat.
• The pancreas secretes enzymes that help
break down food into particles that can be
absorbed by the blood.
Internal
Structure
of a Frog
Characteristics of Amphibians:
Excretory System
• The kidneys are the primary excretory
organ, and filter nitrogenous wastes from
the blood.
• Wastes combined with water are known as
urine.
• Urine flows from the kidneys to the cloaca
and then to the urinary bladder, which
branches off the cloaca.
Characteristics of Amphibians:
Excretory System
• Nitrogenous wastes are converted from
ammonia to urea, which is highly
concentrated and helps conserve water.
Characteristics of Amphibians:
Nervous System
• The olfactory lobes are larger in amphibians than in fish.
• The cerebrum is responsible for behavior and learning.
• The optic lobes process information from the eyes.
• The cerebellum is responsible for muscular coordination.
• The medulla oblongata controls heart rate and
respiration rate.
Characteristics of Amphibians:
Nervous System
Sense Organs • Larvae have a lateral line, most adults do not.
• The eyes are covered by a nictitating membrane,
a transparent moveable membrane that protects
the eye.
Characteristics of Amphibians:
Nervous System
Sense Organs • Sound is detected by the inner ear.
• Sounds are transmitted to the inner ear by the
tympanic membrane, or eardrum, and the columella,
a small bone that extends between the tympanic
membrane and the inner ear.
Reproduction in Amphibians:
Courtship and Fertilization
• Males attract females with a mating call.
• Females only respond to males of the
same species.
Reproduction in Amphibians:
Courtship and Fertilization
• The male clings to the female in an
embrace called amplexus.
• Eggs and sperm are released into the
water.
• Fertilization is external.
Reproduction in Amphibians:
Courtship and Fertilization
• Male - includes two bean-shaped testes
located near the kidneys that produce
sperm during the breeding season.
Reproduction in Amphibians:
Courtship and Fertilization
• Female - includes a pair of large ovaries
containing thousands of tiny immature
eggs. During the breeding season the
eggs mature.
Reproduction in Amphibians:
Life Cycle
• When the eggs hatch, a tadpole is released.
• The tadpole grows and slowly changes from an aquatic larva
into an adult in a process called metamorphosis.
• Metamorphosis is controlled by a hormone called thyroxine.
Reproduction in Amphibians:
Life Cycle
• Some amphibians do not produce thyroxine
and remain in the larval stage their entire life.
• Some amphibians do not have a larval stage
and hatch from the egg as small versions of
the adult.
Life Cycle of Frog
Reproduction in Amphibians:
Parental Care
Parental care increases the likelihood that the
offspring will survive.
• Some species guard their eggs until they hatch.
• Some species sit on their eggs to prevent them
from drying out.
• The male Darwin’s frog carries the eggs in his vocal
sacs until the larvae finish metamorphosis.
• Female gastric brooding frogs swallow their eggs
and the larvae mature in the stomach.