Biomes and Climate
Lesson 4 of 7
Objective: Students will be able to describe the climatic effects of changing latitude, altitude, and seasons and explain why these climatic changes occur.
This lesson is the second part of a two-part lesson that began with "Adaptation to Biomes". Whereas that lesson included a textbook reading and information that covered the "what" of biomes (i.e., an examination of their biotic and abiotic characteristics), this lesson covers the "why" of biomes (i.e., why do different regions of the globe have such vastly different environmental conditions and why do many regions have seasonal variation between conditions at different times of the year?).
Unlike many of my lecture based lessons, this particular lesson does not have a preceding textbook assignment. Rather, students prepare for this lesson by completing the "Biome coloring map" and the "Los Angeles Climatograph" lessons.
The powerpoint itself provides most of the information out of necessity rather than choice, the textbook my class uses doesn't have a chapter or chapters that really cover the concepts presented in this lesson succinctly. Therefore, it's important to do frequent checks for understanding during the presentation, which I'll discuss in more detail in the direct instruction section.
The lesson culminates with students watching the documentary, "Planet Earth: From Pole to Pole", and writing five short paragraphs to communicate their understanding of the topics discussed in this and the preceding lesson.
Connection to Standard:
I begin the lesson by asking students to get out their maps from the "Biomes Coloring Map" lesson and ask students what climatic zone we are in (answer: north temperate zone, better answer: the subtropics of the north temperate zone"). Obviously, depending on your location, your students may offer different information.
I then ask students to discuss in their small groups how our climate is different than Juneau, Alaska or Cancun, Mexico. After just a minute or two of discussion, students share out to the whole group in a short discussion.
Some of the response my students offered were,
- "It's going to be super cold in Alaska"
- "Cancun is nice all the time, that's why people go there for vacation"
I then ask students to discuss in small groups how and why our climate in Los Angeles is different than Big Bear (a mountain resort community approximately 2 hours from LA). Again, depending on your location, this might not be as salient a point for your students if there aren't many students with personal experience with the effects of higher elevations on climate. In that case you may wish to ask about Mt. Kilimanjaro, explaining that it is in Africa but often has snow at its peak in winter. Any example will do, as long as students consider that altitude is an important characteristic of a region's climate.
Getting back to Big Bear versus Los Angeles, some of the response my students offered were,
- "It's cold in Big Bear"
- "There's snow in Big Bear"
- "It's 'fresh' in the summer up there but super hot here"
- "There are more christmas trees in big bear and more palm trees here"
- "wait a minute, why is it colder there? Aren't they closer to the sun?"
After students have shared their responses, I segue into the direct instruction: "As we'll see, the climate of a place is determined by its latitude and its altitude, and a few more factors that we'll discuss". I then have a student volunteer distribute the notesheet for the lesson and we begin the presentation.
Following the quick warm up, I begin the powerpoint presentation for this lesson.
As I've mentioned in previous lessons, offering students a note sheet provides a readymade study guide for later and allows students to focus on their thoughts and the concepts being discussed as opposed to focusing all of their attention on copying down copies amounts of notes.
Wondering WHY I use lectures as a pedagogical strategy? Watch this video.
Wondering HOW I use the Powerpoint to differentiate instruction? Watch this video.
Wondering why I choose to have a reading assignment AND a lecture on the same content? Read this rationale.
Wondering how you might use this lesson's resources if you don't plan on presenting a lecture? Read this reflection.
During the presentation, I make sure to continually solicit student involvement by asking for them to provide personal experiences that might relate to the content and encouraging them to ask questions when they arise.
Please Note: This lesson does not have a direct text reference chapter, so much of the information is being presented to students for the first time. This requires more frequent checks for understanding than during most presentations. I do this by posing questions and asking students to discuss with their groups for a minute or so while I check in with at least one group to ensure they can offer an answer I'm looking for. I then ask for students to share out their answers, knowing that I can rely on at least one group to provide a "correct" response if groups are reluctant to participate.
I find it important to really do thorough checks for understanding on a few points in this presentation by asking the following questions during the presentation:
- "What's the difference between climate and weather?" A: Weather describes the day to day variations in conditions such as temperature, precipitation, wind, humidity, etc. Climate describes the prevailing conditions of a region over a longer period (e.g., the chaparral biome is characterized by warm, dry summers and cool, wet winters).
- "What does latitude measure and how does it affect climate?" A: latitude measures a location's distance from the Equator. As latitude increases, temperature tends to decrease.
- "Why do seasons change?" A: seasons change because the Earth is tilted on its axis, meaning at different times of the year, one or the other hemisphere is tilted in the direction of the sun and receives more direct sunlight and therefore experiences warmer temperatures. This is especially important to clarify as many graphics seem to indicate that the distance of the Earth from the sun changes throughout the year. This misconception can quickly be dispelled if you point out that if this were the case, we would experience two summers and two winters per year.
- "How does altitude affect temperature? Why does this happen?" A: Like latitude, as altitude increases, temperature decreases. This happens because air at higher elevations is less dense and lower air pressure corresponds with lower temperatures.
- "How can mountains affect precipitation?" A: Mountains can form a "rain shadow" where clouds on the windward side of a mountain release their precipitation as they ascend to cooler air, leaving the leeward side of the mountain comparatively very dry.
- "What is convection and how does it affect climates?" A: Convection is a property of fluids where cool, dense fluids sink and warm, less dense fluids rise. Convection currents in the air cause wind and weather patterns to differ (e.g., warm air at the tropics constantly rises and releases its moisture back down as precipitation). Convection currents in the water can create currents where cooler water from the poles sinks under warmer water from the tropics. This can creates streams that affect regional climates (e.g., Western Europe experiences warmer temperatures than other regions at similar latitudes because of the warm waters of the Gulf Stream).
Film: From Pole to Pole
We end this lesson by viewing the excellent documentary "From Pole to Pole" from the BBC's Planet Earth series.
Following the powerpoint presentation, I distribute the viewing guide and quickly review the instructions. After checking to make sure that students understand they will be taking notes from the film about specific cases of organisms adapting to different environmental conditions in order to prepare for a short writing assignment, I begin the film.
After the first 5 minutes (the section dealing with polar bears) I ask students to connect to the both this lesson and the adaptations to biomes and biome coloring map lessons by asking the following questions:
- "Where were the bears?" in their den (an example of a burrowing adaptation)
- "Why were they there?" they were hibernating
- "Why did they need to hibernate?" the polar regions have incredibly cold, long winters
- "Why does the sun not set?" because they are above the arctic circle
I then explain to students that as they view the rest of the documentary, they should be taking notes similar to the way we just broke down the first scene.
The notes that they take will then be used to complete their writing assignment detailed in the viewing guide. Since the film takes up the remainder of class time, the expectation is that students will just be taking notes from the film in class, and will complete their writing assignment as homework. Prior to releasing students at the end of class, I also let them know that these written questions will be very similar to the short essay questions on their unit test, so it would behoove them to put as much effort into the writing now as it will have a significant payoff later.
When the time comes on the next class meeting to turn in this written assignment, I have the students have short discussions of their writing with their groups, and then I ask for students to share out examples of specific adaptations to environmental conditions in different biomes discussed in the film.