Kean University Continuing Education

Implementing the Science Standards K-4


Frog Life Cycle

Introduction

There are five classes of vertebrate animals. These include fish, amphibians, reptiles, birds and mammals. The frog is an example of the amphibian class. Amphibians spend part of their life cycle in water and part on land.

The life cycle of a frog begins with a fertilized egg. The fertilized egg develops into a tadpole. The fertilized egg and tadpole stages are found in the water in the spring. The tadpole develops into an immature frog.

As the immature frog develops it is transformed via the process of metamorphosis into an adult frog. The tail is absorbed and the external gills are replaced by lungs. The adult frog lives on land and in the water and breathes air. The adult frog uses its skin for about 50% of its gas exchange, meaning that it breathes through its skin. Therefore, a frog will not stay out of water long enough for its skin to dry out. As it is said, "A dry frog is a dead frog."

Materials

Procedure

Students identify and write about the stages of the frog life cycle in their Science Journals. They make notes about the following information.

Results

1. Students draw an illustrated life cycle in their Science Journals. This shows each of the stage in its proper sequence. They label each of the stages with proper words.

2. Students describe the stages of the life cycle by writing a paragraph for each one. The paragraph should state their findings for each stage including

3. Students prepare reports on the frog life cycle. These reports can be submitted for grading or presented in a variety of ways.

Discussion

1. Students research the average length of time it takes for the frog life cycle from the beginning to the death of the adult frog.

2. Students use the life-span information for the frog to determine the percentage of the life cycle the frog spends in each stage. This is made into a table which they write in their Science Journals.

Stage of Life Cycle Percentage of Time
Egg ____________
Tadpole ____________
Immature frog ____________
Mature frog ____________

Note that in doing this activity, the same unit must be used. The percentage numbers will only be valid when both numerator and denominator are the same units. Students should try it several times using days, weeks or months as units of time.

3. Students research the ecological role that each stage of the life cycle of the frog plays. This is also related to diet. Students research what the diet is for each of the stages of the frog. Students compare frog data with those of other amphibians such as toads and salamanders.

4. Students can make a food chain or several food chains containing stages of frog development. These food chains will show the position of the frog in the food chain at various stages of development. They draw the food chains in their Science Journals.

5. Students consider what happens during the course of the frog life cycle if something goes wrong. They investigate what events would cause the life cycle not to be completed. Examples:

Students relate the answers to these questions to the way the frog lives and reproduces. For example, the frog produces large numbers of eggs so that the chances of survival of the species are greater.

6. Students consider the adult frog or the stages of the frog life cycle. They investigate what would be the outcome if there were a severe drought during the year or for several years. Also, what would be the effect on frogs in years when there is abundant rainfall.

7. Students investigate the effects of environmental pollution on frogs. They record their findings in their Science Journals.