This lesson asks students to make a map of global biome distribution and then interpret that map to answer reflective questions. Necessary supplies for this lesson will be colored pencils, rulers, and some reference map of global biome distribution, whether from a textbook or an online source.
Since this lesson precedes the lesson on biomes and climate which largely focuses on the concept of climactic zones, an essential part of this map-making activity includes delineating the 5 climatic zones of Earth based on key lines of latitude such as the Tropic of Cancer, the Artic Circle, the Equator, etc.
Please note that the map students make as the final product of this lesson will be used in the succeeding climatograph lesson as well.
Connection to Standards:
In this lesson, students will follow a complex, multi-step procedure and then analyze the results of that procedure to develop a coherent understanding of a topic. Students will also observe patterns to infer causal mechanisms to better explain natural phenomena.
I begin this lesson with a quick review of the concept of a biome. Although the word "biome" may not be immediately familiar to all students, they are probably all familiar with the concept, so I help them by saying something like, "you know... a desert is a biome, a rainforest is a biome". Hopefully students can arrive at either their own explanation of what a biome is or, if necessary, provide the textbook definition that says that a biomes are ecoysystems with similar biotic and abiotic characteristics.
I quickly review the vocabulary inherent in this definition:
After that quick review of vocabulary, I ask students to look at a page in their textbook where there is a map of the biomes of the world. If you do not have such a picture in your textbook, I suggest providing a link to a web image of biome distribution such as this map. Another option would be to ask students to use computers or their mobile devices to find their own map online.
Once students are looking at a map, I ask, "Are the different biomes found only in one place?", A: No, they occur in different areas and on different continents.
Some students may point out, however, that there is a pattern of distribution. For example, they may notice that tundra only occurs on the far northern areas of the continents in the Northern Hemisphere.
I then ask students what kinds of ways the non-living characteristics of two different places could be similar. Answers will vary and can include things like "the land", "the weather", "how much water there is", "if there are buildings", etc. As students offer their ideas, I write them on the board. We do this until we stumble upon the idea that different areas can have similar climates, defined as having similar patterns of temperature and precipitation.
I then explain that we will be making a map of the world, separating it into 5 climatic zones, and then mapping the distribution of the major biomes of the world.
Once the intro is over, I ask for a volunteer to pass out the map and instructions. I print them double-sided, but if you print them on separate sheets you may want to have two students hand out the two sheets to save time. I then ask each group to send one member to pick up rulers and colored pencils for their group.
Once all groups have their maps, instructions, and supplies, we look at the map and I ask if the horizontal lines are lines of latitude or longitude. If students are split, I remind them of the So Cal mnemonic, "latitude is flat, dude". I may also start singing the Jimmy Buffett song, "Changes in Latitudes, Changes in Attitudes", if I'm feeling especially corny at the time.
Once we have established that the horizontal lines are lines of latitude, not longitude, I ask students, "What is the sigificance of the line marked 0 degrees?", A: the Equator. I then ask, "What is the weather like at the Equator?", A: very hot!
I then point them all the way to the top, and ask them, "Does anyone know what's at 90 degrees of North latitude?", A: the North Pole.
The answer to this can be tricky, because the flat map makes it seem as if this line goes across the top of the entire world. If students don't get the answer fairly quickly, I give them the hint, "Santa Claus lives there". That should do it. I then ask, "What's the weather like at the North Pole?", A: It's very cold!
I then explain the same pattern holds true for the Southern Hemisphere: temperatures decrease as latitude increases. I then explain that we will be using this fact to divide the map into 5 climatic zones.
I then reference the instructions and ask the students what line they need to draw first, they reply the Tropic of Cancer at 23.5 degrees North. I ask them if 23.5 degrees is a line on the map already and they reply no, that there are only lines at 0, 30, 60, and 90 degrees. I let them know that part of what makes this map tricky, is that they'll have to make their own estimation of where 23.5 degrees will fall on their map.
I then ask them to look at the next section and ask them which line they'll draw after the tropics, to which they reply 66.5 degrees North, the Arctic circle. I explain that, in the Northern hemisphere, areas North of this line are called the polar regions and are the coldest on Earth. I explain that between the Arctic Circle and the Tropic of Cancer, we find the Temperate Zones, where the climate varies a lot depending on the season. I finally explain that these lines are mirrored in the Southern Hemisphere, and that between the Tropic of Cancer and the Tropic of Capricorn, the Tropical regions are the hottest on Earth.
I then explain that students will have to carefully place these key lines of latitude on their maps and then carefully label the 5 climatic zones. I let them know that once they have their lines set, they can begin using their textbook or an online map of biome distribution to color in the locations of the different biomes around the Earth. I make sure to mention that they need to keep the characteristics of the 5 climate zones (i.e., are they close or far from the equator) in mind as they complete their maps, as any patterns of distribution they notice will help them complete the map analysis and reflection at the end of the lesson.
After students have finished making their maps, they should begin working on the follow up questions found on the instructions worksheet. These questions ask students to look for patterns of distribution and describe which biomes are found mostly or exclusively in the polar regions, temperate zones, or tropics.
During this time, I walk around to help students that are having trouble piecing together the patterns of biome distribution on the maps before them. Usually this just means saying something like, "Point to a section of rainforest, ok, what climatic zone is that located in? Do you see it anywhere outside of that climatic zone? Ok, then you've noticed a pattern of distribution, write that down." etc.
The final question asks students to describe any other patterns they may notice. Answers will vary, but a common observation is that deserts occur around 30 degrees of latitude in both hemispheres (this is explored in detail in the biomes and climate lesson). This example shows that this particular student was able to notice several patterns in the geographic distribution of the biomes. I encourage students to work on these questions cooperatively with their group members, but I keep moving around the room to make sure no one is just copying another student's observations.
In the last 10 minutes or so, I like to have a short discussion of the reflection questions. Usually I ask for one volunteer to answer a question, then solicit any addenda that other students may want to offer before moving on to the next question. For the final question about patterns and trends in the map, I try and get more students involved and I write as many of their observed patterns on the board as possible For example,
It's possible to make this discussion longer or shorter if you wish by asking follow up questions that ask students to make predictions about why these patterns exist. These follow-up questions could be a good lead in to the next lesson on biomes and climate so whether you hold this discussion at the end of this lesson or the beginning of the next is up to you.
For my part, I intended to have this short discussion of the reflection questions at the end of class, but I had a few groups that were taking a long time coloring their maps in meticulous detail, so I assigned the completion of the map and reflection questions as homework for any students that hadn't finished and saved the discussion until the start of the next class.