Slide 1 of 47 Copyright Pearson Prentice Hall Biology
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Slide 2 of 47 Copyright Pearson Prentice Hall 30-3
Amphibians
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Slide 3 of 47 Copyright Pearson Prentice Hall What Is an
Amphibian? What is an amphibian?
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30-3 Amphibians Slide 4 of 47 Copyright Pearson Prentice Hall
What Is an Amphibian? An amphibian is a vertebrate that, with some
exceptions: lives in water as a larva and on land as an adult
breathes with lungs as an adult has moist skin that contains mucous
glands lacks scales and claws
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30-3 Amphibians Slide 5 of 47 Copyright Pearson Prentice Hall
Evolution of Amphibians How are amphibians adapted for life on
land?
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Evolution of Amphibians The first amphibians appeared in the late
Devonian Period, about 360 million years ago. The transition from
water to land required that the terrestrial vertebrates had to:
breathe air, protect themselves and their eggs from drying out, and
support themselves against the pull of gravity.
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30-3 Amphibians Slide 7 of 47 Copyright Pearson Prentice Hall
Evolution of Amphibians Early amphibians evolved several
adaptations that helped them live at least part of their lives out
of water. Bones in the limbs and limb girdles of amphibians became
stronger, permitting more efficient movement.
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Evolution of Amphibians Lungs and breathing tubes enabled
amphibians to breathe air. The sternum formed a bony shield to
support and protect internal organs, especially the lungs.
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Evolution of Amphibians Amphibian Adaptations Pelvic Girdle Lungs
Leg Bones: The legs of a land vertebrate must be strong enough to
hold its weight. Skin: The skin and the lining of the mouth cavity
of many adult amphibians are thin and richly supplied with blood
vessels. Watery mucus is secreted by glands in the skin.
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Evolution of Amphibians In many adult amphibians, the internal
surfaces of the lungs are richly supplied with blood vessels and
folds that increase surface area. Lungs
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Form and Function in Amphibians The class Amphibia is relatively
small and diverse.
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Form and Function in Amphibians Feeding Tadpoles are typically
filter feeders or herbivores that graze on algae. Their intestines
help break down hard-to-digest plant material and are usually
filled with food. The feeding apparatus and digestive tract of
adults are meat-eating structures.
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Form and Function in Amphibians Frog Anatomy
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Form and Function in Amphibians Adult amphibians are almost
entirely carnivorous. Many salamanders and frogs have long, sticky
tongues specialized to capture insects.
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30-3 Amphibians Slide 15 of 47 Copyright Pearson Prentice Hall
Form and Function in Amphibians In a frogs digestive system, food
slides down the esophagus into the stomach. Stomach Esophagus
Mouth
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Form and Function in Amphibians The breakdown of food begins in the
stomach and continues in the small intestine. Stomach Small
intestine
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Form and Function in Amphibians The liver, pancreas, and
gallbladder secrete substances that aid in digestion. Gallbladder
Liver Pancreas
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Form and Function in Amphibians At the end of the large intestine
is a muscular cavity called the cloaca, through which digestive
wastes, urine, and eggs or sperm leave the body. Cloaca Large
intestine (colon)
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Form and Function in Amphibians Respiration In most larval
amphibians, gas exchange occurs through the skin and the gills.
Adult amphibians typically respire using lungs, but some gas
exchange occurs through the skin and the lining of the mouth.
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Form and Function in Amphibians Circulation In frogs and other
adult amphibians, the circulatory system forms a double loop. The
first loop carries oxygen-poor blood from the heart to the lungs
and skin, and takes oxygen-rich blood from the lungs and skin back
to the heart.
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Form and Function in Amphibians The second loop transports
oxygen-rich blood from the heart to the rest of the body, and
carries oxygen- poor blood from the body back to the heart.
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Form and Function in Amphibians Amphibian Circulation and Excretion
Heart Lung Kidney Ureter Cloaca Urinary bladder
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Form and Function in Amphibians The amphibian heart has three
separate chambers: left atrium right atrium ventricle
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Form and Function in Amphibians Amphibian Heart Right atrium Left
atrium Ventricle From Body To body, lungs and skin From Lungs
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Form and Function in Amphibians Excretion Amphibians have kidneys
that filter wastes from the blood. Urine travels through tubes
called ureters into the cloaca. Urine is then passed directly to
the outside, or temporarily stored in a small urinary bladder just
above the cloaca.
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Form and Function in Amphibians Reproduction In most species of
amphibians, the female lays eggs in water, then the male fertilizes
them externally. In a few species, including most salamanders, eggs
are fertilized internally. After fertilization, frog eggs are
encased in a sticky, transparent jelly.
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30-3 Amphibians Slide 27 of 47 Copyright Pearson Prentice Hall
Form and Function in Amphibians The jelly attaches the egg mass to
underwater plants and makes the eggs difficult for predators to
grasp. The yolks of the eggs nourish the embryos. Most amphibians
abandon their eggs after they lay them. A few amphibians take care
of both eggs and young.
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30-3 Amphibians Slide 28 of 47 Copyright Pearson Prentice Hall
Form and Function in Amphibians Frog Metamorphosis Adult Frog Young
Frog Fertilized eggs Tadpoles
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Form and Function in Amphibians Adults are typically ready to breed
in about one to two years. Frog eggs are laid in water and undergo
external fertilization.
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Form and Function in Amphibians The fertilized eggs hatch into
tadpoles a few days to several weeks later. Fertilized eggs
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Form and Function in Amphibians Tadpoles gradually grow limbs, lose
their tails and gills, and become meat-eaters as they develop into
terrestrial adults. Young frog Tadpole
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Form and Function in Amphibians Movement Amphibian larvae move by
wiggling their bodies and using a flattened tail for propulsion.
Adult salamanders walk or run. Frogs and toads, have well-developed
hind limbs that enable them to jump long distances.
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Form and Function in Amphibians Response Amphibians have
well-developed nervous and sensory systems. An amphibian's eyes are
protected from damage and kept moist by a transparent nictitating
membrane. This membrane is located inside the regular eyelid and
can be closed over the eye.
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Form and Function in Amphibians Amphibians hear through tympanic
membranes, or eardrums, located on each side of the head. Many
amphibian larvae and adults have lateral line systems that detect
water movement.
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Form and Function in Amphibians Frogs Sense Organs
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Groups of Amphibians What are the main groups of living
amphibians?
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Groups of Amphibians The three groups of amphibians alive today
are: salamanders frogs and toads caecilians
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Groups of Amphibians Salamanders Salamanders and newts have long
bodies and tails. Most have four legs. Both adults and larvae are
carnivores. Adults usually live in moist woods, where they tunnel
under rocks and rotting logs.
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30-3 Amphibians Slide 39 of 47 Copyright Pearson Prentice Hall
Groups of Amphibians Frogs and Toads Frogs and toads have the
ability to jump. Frogs tend to have long legs and make lengthy
jumps. Toads have relatively short legs and are limited to short
hops.
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Groups of Amphibians Frogs are generally more closely tied to water
than toads. Toads often live in moist woods and even in
deserts.
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Groups of Amphibians Caecilians Caecilians are legless animals that
live in water or burrow in moist soil or sediment. Caecilians feed
on small invertebrates such as termites. Many have fishlike scales
embedded in their skin.
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Pearson Prentice Hall 30-3
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Slide 43 of 47 Copyright Pearson Prentice Hall 30-3 The word
amphibian refers to the ability to a.live in hot climates. b.live
in wet places. c.live both in water and on land. d.live in cold and
hot climates.
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Slide 44 of 47 Copyright Pearson Prentice Hall 30-3 Fossil
evidence indicates the first land amphibians appeared during the
a.Jurassic Period. b.Devonian Period. c.Cambrian Era. d.Cretaceous
Era.
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Slide 45 of 47 Copyright Pearson Prentice Hall 30-3 In a larval
amphibian, gas exchange occurs through a.the skin only. b.both the
skin and the gills. c.the gills only. d.a lung.
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Slide 46 of 47 Copyright Pearson Prentice Hall 30-3 The
tympanic membrane in a frog enables it to a.hear. b.see. c.smell.
d.taste.
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Slide 47 of 47 Copyright Pearson Prentice Hall 30-3 Which of
the following is a group of amphibians living on the Earth today?
a.crocodiles b.snakes c.salamanders d.lizards