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Frogs Jump, Toads Hop, Salamanders Crawl! (GMHDRNC)

TopicWildlife - Amphibians
Summary
Learn about the life cycle, habitats and behavior of frogs, toads and salamanders as well as the differences among these three amphibians.
Grade LevelK - 12
Recommended SettingIndoor or outdoor classroom
LocationGovernor Mike Huckabee Delta Rivers Nature Center, Pine Bluff
Contact

Education Program Coordinator, 870-534-0011

Duration45 minutes - 1 hour
Suggested Number of Participants10 - 30
Objectives
  • Learn the different characteristics of the amphibians.
  • See how they are different from other animals.
  • Understand the life cycle of amphibians.
Key Terms*

Amphibian

Frog

Metamorphosis

Neoteny

Paratoid

Salamander

Toad

Materials

Life cycle diagram

Live animals

Background

Amphibians are cold-blooded and lay their eggs in the water. Most amphibians have soft skin which easily absorbs water. This puts them in close contact with their surroundings and makes them susceptible to man-made toxins. This may explain why the number of amphibian species and the size of many amphibian populations have declined recently.

Procedure
  1. Discuss the features that classify an animal as an amphibian. Amphibians, along with birds, reptiles, mammals and fishes, are vertebrates–-creatures with a backbone and an internal skeleton. “Amphibian” means “double life” and refers to the fact that amphibians live part of their lives in water and part on land. All amphibians go through metamorphosis. Even species that lay eggs on land start life in a fluid-filled egg, breathing through gills. There are three kinds of amphibians in Arkansas: toads, frogs and salamanders. Emphasize that “frogs jump, toads hop and salamanders crawl!”
  2. Frogs have smooth, wet skin with long legs for jumping up to 20 times their body length, equal to a 100-foot jump for the average human. Tell participants about some physical adaptations of frogs.
    • Frogs eat almost any live prey they can swallow, including insects, snails, spiders, worms, and even small fish. Some frogs catch insects with a long, sticky tongue. It takes less than a second for a frog's tongue to roll out, adhere to prey and roll back into the frog's mouth. Not all frogs have tongues. Tongueless frogs use their fingers to catch prey and stuff it into their mouths. All prey are swallowed whole because frogs can't chew. If they have teeth, they are usually only on the upper jaw, used for holding prey and not for biting or chewing. Catching fast-moving insects requires good eyesight. Frogs' large eyes see a wide range of colors and also see well in dim light. But they also have a surprising auxiliary function: they help in swallowing. As a frog swallows its prey, the eyes sink through openings in the skull and help force the food down the throat.
    • Frogs must keep their skin moist because if oxygen can't pass easily through the skin, the frog suffocates. Frog skin secretes mucus that keeps it moist. Even so, their skin tends to dry out easily, which is why they usually stay near water.
    • Frogs make their calls with one or two pouches of skin called vocal sacs. Sound is produced when air rushes over the vocal chords on its way from the lungs into the vocal sacs. The vocal sacs work like echo chambers to amplify the sound.
  3. Generally toads have dry skin with warts and short legs for hopping. Point out the differences between frogs and toads. Toads' skin doesn't lose moisture as quickly, so they can live farther from water than most frogs. In a pinch, frogs and toads can rely on dew for moisture or burrow underground into moist soil. Toads also use poison, which is behind their eyes in a pair of poison glands called parotoid glands. When the toad is threatened, a milky, poisonous fluid oozes from the glands. The poison is stronger in some toads than others, but even in its mildest form it causes a burning sensation if it gets in the eyes.
  4. Salamanders belong to the order Caudata, from the Latin word “cauda” meaning “long tail.” Discuss the basic biology of salamanders.
    • There are nine families of salamanders, eight of them in North America. They are among the most abundant vertebrates in the southeast United States, inhabiting upland wooded forests to streams and swamps. Despite their abundance (more than 30 species in Arkansas alone), they are relatively inconspicuous, remaining out of sight most of the year.
    • Many salamanders, such as the spotted salamander, exhibit biphasic life cycles with metamorphosis separating the larval (tadpole) and adult stages. Other species, such as the slimy salamander, do not have a free-living larval stage and complete metamorphosis inside the egg. Still other species, such as the siren, have abandoned metamorphosis and remain in the larval stage while reproducing like "normal" adults. This is a classic example of an evolutionary phenomenon known as neoteny, the retention of larval or juvenile features in mature adults.
  5. Answer any questions.
Review
  • Can frogs chew their food?
  • What is unique about sirens within the amphibian family?
  • Why do toads use their poison?
Related Documents
Glossary

Amphibian – any cold-blooded, egg-laying vertebrate of the class Amphibia having gilled aquatic larvae and air-breathing, semiterrestrial adults; examples are frogs and toads, newts and salamanders and caecilians

 

Frog – any tailless, stout-bodied amphibian of the order Anura, including the smooth, moist-skinned frog species that live in a damp or semi-aquatic habitat and the warty, drier-skinned toad species that are mostly terrestrial as adults

 

Metamorphosis – a change in the form and often habits of an animal during normal development after the embryonic stage. Examples include a maggot changing into an adult fly and a caterpillar into a butterfly, and in amphibians, the changing of a tadpole into a frog.

 

Neoteny – juvenile characteristics retained in the adult organism, or sexual maturity in an organism still in its larval stage: also called pedogenesis

 

Paratoid – large wart-like glands on the side or back of a toad’s head

 

Salamander – any tailed amphibian of the order Caudata that has a soft, moist, scaleless skin, typically aquatic as a larva and semi-terrestrial as an adult: several species are endangered

 

Toad – any of various tailless amphibians that are close relatives of the frogs in the order Anura and that typically have dry, warty skin and are terrestrial or semi-terrestrial