Let’s make a model of frog & turtle

Use this hands-on model to make comparisons about the body and skin of amphibians and reptiles! 

Materials 

• Construction paper & marker
• Sponge & water
• Sock (or other fabric scrap)
• Plastic bag 
• Image of frog and turtle (below)

Let’s get started 

Using the images to introduce frog and turtle, observe the two animals. Compare and contrast what you see! As appropriate and of interest to your herpetologist, introduce a few other examples of other amphibians (like toads, salamanders, and newts) and reptiles using video clips or images online. 

Explain that even though these animals have some similarities, they are actually very different. We’re going to use a fun model to learn more about what makes them different! We’re going to focus on their skin and bodies. 

Label the two halves of your construction paper frog and turtle. 

Amphibians 

Let’s make a model of frog’s body and skin first. Wet the sponge in a bowl of water or under the tap, then gently squeeze out excess water from the sponge. What do you notice? (the sponge is wet). This represents the inside of a frog’s body! Like some other animals, a frog’s body is made up of lots of water. Place the sponge in the sock or wrap it in fabric. Ask your scientist what we are representing with the sock or fabric (the outside/skin of the frog). 

Very gently press the model onto your construction paper! Ask what they noticed? Ask students what this model shows us about frogs’ skin (it’s wet and water can move through it!) Ask students what they think would happen if this model was out of the water for a long time (it would dry out).

Reptiles

Next, let’s make a model of a reptile’s body and skin. If needed, wet the sponge in a bowl of water or under the tap again and then gently squeeze the sponge. What do you notice? (the sponge is wet). This represents the inside of turtle’s body now! Place the sponge in a plastic bag. Ask your scientist what we are representing with the plastic bag now (the outside/skin of turtle). 

Very gently press the model onto the turtle side of your construction paper! Ask what they noticed? (the paper is not wet/not very wet).  Ask students what this model shows us about turtle’s’ skin. Ask students what they think would happen if this model was out of the water for a long time? 

Compare

Compare the two models. Consider: Which model would dry out first? What does this model show us about frog and turtle skin? 

Use the background information below and share additional ideas and connections with your junior herpetologist! 

Additional Information for Grown Ups 

Reptiles and amphibians are two of the classes in the Linnaean classification system. While they may seem similar in some ways, they actually differ in many important ways. Reptiles and amphibians are both ectotherms (cold-blooded). They depend on heat from the sun or environmental cooling to regulate their body temperatures. Herpetology is the study of reptiles and amphibians. 

Amphibians include frogs, toads, salamanders and newts. Amphibians live part of their life on land and part of their life in water.  Most amphibians go through metamorphosis. For example, frogs start their life cycles as tadpoles in the water before metamorphosing into frogs that live on land. Amphibian skin is permeable – it allows water and gasses to move freely.  Because of this, amphibians must live in wet environments either by living directly in the water or in wet environments such as leaf litter. Amphibians can also act as indicator species because, due to their permeable skin, they are quickly affected by pollution. Amphibian eggs don’t have a protective membrane and are laid in the water to prevent them from drying out. 

Reptiles include turtles, snakes, lizards, alligators, and crocodiles. Reptiles are vertebrates with backbones and have dry, scaly skin. Their scaly skin helps them conserve water because it prevents evaporation. By conserving water, reptiles are generally able to live in drier environments than amphibians. As reptiles grow, they will shed their scales and the scales are replaced. Turtle’s shell will grow with it during its whole life! Reptiles tend to lay hard-shelled/leathery eggs.