30-3 Amphibians - classroom.libertychristian.comclassroom.libertychristian.com/.../17909/12Ch.30-2-amphibians.pdf · 30-3 Amphibians Slide ... Form and Function in Amphibians The

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30-3 Amphibians

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What Is an Amphibian?

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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Amphibians

Amphibian Characteristics

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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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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Frog Anatomy

Resources/Movies/vafrogan.mov

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Adult amphibians are almost entirely carnivorous.

Many salamanders and frogs have long, sticky

tongues specialized to capture insects.

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In a frog’s digestive

system, food slides down

the esophagus into the

stomach. Stomach

Esophagus Mouth

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The breakdown of food

begins in the stomach

and continues in the

small intestine. Stomach Small intestine

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The liver, pancreas, and

gallbladder secrete

substances that aid in

digestion.

Gallbladder Liver

Pancreas

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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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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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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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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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Amphibian

Circulation and

Excretion Heart

Lung

Kidney

Ureter

Cloaca

Urinary

bladder

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The amphibian heart has three separate chambers:

•left atrium

•right atrium

•ventricle

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Amphibian

Heart

Right

atrium

Left

atrium

Ventricle

From

Body

To body,

lungs and

skin

To body,

lungs and

skin

From

Lungs

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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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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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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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Frog Metamorphosis

Adult

Frog

Young

Frog

Fertilized

eggs

Tadpoles

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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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The fertilized eggs hatch into tadpoles a few days

to several weeks later.

Fertilized eggs

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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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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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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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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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Frog’s Sense Organs

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Groups of Amphibians


The three groups of amphibians are:

• salamanders

• frogs and toads

• caecilians

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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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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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Frogs are generally more closely tied to water than

toads.

Toads often live in moist woods and even in deserts.

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Caecilians

Caecilians are legless animals that live in water or

burrow in moist soil or sediment.

Caecilians feed on small invertebrates such as

termites and resemble large worms.

Many have fishlike scales embedded in their skin.

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30-3 Amphibians - classroom.libertychristian.comclassroom.libertychristian.com/.../17909/12Ch.30-2-amphibians.pdf · 30-3 Amphibians Slide ... Form and Function in Amphibians The