I start out with this question:
If frogs and toads need water, why do they want to live in the desert?
I ask them to think and write for a few minutes, silently, and then discuss their ideas with a peer. I monitor but don't intercede. As a teacher, what I am looking for is a growing awareness that animals most often are not making choices, but are trying to survive in the environment in which they find themselves. Then I call on a few of them to share their thoughts, which I do both to develop scientific understanding and as part of my constant integration of developing their ability to write and speak in strong, clear, concise sentences.
Here are two students giving their answers. The first child speaks English as a second language but he pays attention to new vocabulary and his ability to speak in completely, clear sentences has really developed.
Here is another bilingual student. He has a tremendous number of ideas and faces the common third grade challenge of getting all those ideas down on paper or typed into a doc. You can see that he has a very circular pattern of discourse.
Next, I tell students that we are going to look at two different locations, one arid (Arizona) and one that is more temperate and receives a fair amount of rain (North Carolina). We will hypothesize about the type and quantity of amphibians in each location and then look at actual data. Before we do that, though, we will review the definition of an amphibian! Prior to going through the PowerPoint, I ask them to write down one thing they know about amphibians on their study guide.
Then I go through this Introduction to Amphibians presentation. After that, I ask them to estimate the number of species of different amphibians that live in Arizona (a very arid to semi-arid state) and North Carolina (a wetter, more temperate state).
Then I use the answer key to give them the actual numbers. Next, to maintain their interest in this understudied animal group, I created this short video with pictures of many of the diverse species of frogs we have in the United States.
I ask students to discuss what their thoughts are about whether or not frogs need a permanent water source. The way my students respond is going to be different from the ways in which students from wetter regions of the country respond. I ask them these questions and walk around to monitor their discussions. I place them in groups.
Why does North Carolina have more amphibians if it's a smaller state?
Do you think frogs use permanent water more in North Carolina than they do in Tucson? Explain.
What response to the environment do you think frogs in Arizona may share with frogs in North Carolina?
Why do you even need to know this about frogs?
Then I provide them with these two data sheets about Arizona Frogs Habitats and North Carolina Frogs Habitats. I ask them to tally up the number of species that use each kind of environment: permanent water, temporary water, and human made watery environments. I also ask them to star frog species that prefer temporary water.
The question I post on the board during this section of the lesson is: Why do so many frogs prefer temporary water sources? (Lack of predators).
Another question for them to think about is the definition of temporary. In the Sonoran Desert of Arizona, even the deepest of rain pools can dry out in a week, whereas in North Carolina, especially in the _________, temporary pools of water may last for months.
The concluding activity in this lesson is to make a double bar graph showing how many species from each state use each of the general water environments (permanent, temporary, or human made). Putting the data into such a visible format provides them with great support for discussing what they discovered and also gives them a mathematical and scientific springboard (as well as the language support provided by visual aids) to extend this thinking further and possibly apply it to other animals and environments.
I ask students to write down at least one thing they've learned today about how frogs survive in different environments and what their requirements for water are. I, for one, assumed that more frogs in wet climates relied on permanent water but upon reflection, the preference for temporary water makes sense as far as survival is concerned!
If you have students who are interested in how amphibians are grouped, this (phylogenetic) amphibian tree from Amphibiaweb is fantastic.
Here is a list of all the amphibian species in the world, as of November 30, 2014. I'm always looking for ways to help students see large numbers in real world context, and what better way than for them to understand how many different frogs and salamanders there are in the world!
For students who like checklists, here is a cheklist of amphibians and reptiles of North Carolina created by the North Carolina Museum of Natural History.