Adaptations to Biomes
Lesson 3 of 7
Objective: Students will be able to describe some of the common adaptations that enable plants and animals to thrive and adapt to different environmental conditions.
This lesson is the first part of a two-part lesson that continues in "Climate and Biomes". Unlike many of the lecture style lessons in my class, these lessons present information from multiple text sources rather than just a particular chapter or chapters.
Rather than look at the individual characteristics of each biome (which students will do later in the unit by making their own collective presentation in the Biomes Cooperative Presentation lesson) this particular lesson looks at how organisms adapt to both the extreme environmental conditions of biomes (e.g., the daily precipitation in a rainforest versus the relative drought of a desert) and the seasonal variations within a biome (e.g., the wet and dry seasons of the chaparral).
Although it doesn't cover all of the concepts discussed in this presentation, students prepare for this lesson by completing a textbook assignment that covers the basic biomes of the world:
- Boreal Forest (Taiga)
- Temperate Deciduous Forest
- Temperate Grassland (Prairie)
- Temperate Rain Forest
- Tropical Dry Forest
- Tropical Grassland (Savannah)
- Tropical Rain Forest
This assignment asks students to read a basic overview of the major biomes of the world and choose two to summarize by collecting some very basic information from the text. Students write this data in the tables on the assignment worksheet.
The textbook chapter comes from Environmental Science: Your World, Your Turn by Jay Withgott, and lists basic information about each of the major biomes including average temperatures, precipitation, geographical distribution, and common plants and animals. The chapter also includes a world map showing the geographical distribution of all biomes which students use to make their own biome map in the Biome Coloring Map lesson.
If you do not have that particular textbook, I would recommend finding a similar chapter or chapters in your textbook and modifying the lesson accordingly.
Alternately, the powerpoint attached to the Direct Instruction section covers most of the same concepts and vocabulary as the chapter. However, a text reference with basic information on all the biomes is a good resource for multiple lessons in this unit. Most environmental science and biology textbooks do have a chapter or chapters that provide an overview of biomes, so I strongly recommend you at least identify appropriate text chapters for your students to use as a resource.
In my case, I assign the textbook reading on the meeting previous to this lesson so that students come to class with at least a basic understanding of the differences between biomes and how certain species have adapted to the differing conditions between biomes.
Connection to Standard:
In this lesson, students will prepare for class by reading and determining the central idea of a text, establish familiarity with relevant scientific vocabulary, and then draw evidence from the text to support arguments and opinions presented as part of their participation in a group discussion.
I begin this lesson with a quick warm up to get students thinking about the idea of how behavior can change depending on seasonal changes in the environment.
I first pose the following questions:
- "How does your behavior change in winter compared to summer?"
- "How does your body physically respond to the change from winter to summer?"
Students then discuss these questions in their small groups. After a few short minutes (during which I walk around "eavesdropping" on students' conversations), students share out response to the questions to the whole group in a short discussion.
Some of the things that my students mentioned were:
- "In summer I go to the beach, in winter I go snowboarding"
- "In summer I wear shorts and a tank top, in winter I wear pants and a jacket"
- "In summer I stay out late, in winter I'm home pretty early"
- "In summer I sweat, in winter I shiver and say 'brrrrr...'"
Keep in mind that most of my students have only lived in Southern California or warmer environments (e.g., Central America), so their perception of "seasonal change" might be quite different to your students, depending on your location.
After this quick warm up, I segue into the direct instruction by saying, "Like us, all organisms respond to their environments in different ways, depending on the conditions."
I then ask for a student volunteer to distribute the lesson's notesheet 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: I find it important to really do thorough checks for understanding on a few points in this presentation:
1. The concept of dormancy doesn't really have a direct correlation to human adaptations (considering that we evolved in an African climate without much seasonal variation), so it can seem somewhat foreign to students' own experience (sleep might be the best analogue, however imperfect). One way to make it clearer to the students is to have them contrast the different types of dormancy. Hibernation and estivation are both examples of animal dormancy, but occur in response to cold temperatures and dry conditions, respectively. Deciduous plants that annually shed their leaves also exhibit a type of dormancy which can also be a response to cold conditions or dry conditions. In this case, the same response protects against different dangers: freezing damage and water loss (freezing temperatures can destroy broad leaves and trees can lose too much water in dry conditions due to transpiration). This can set up a short discussion of the advantages of evergreen trees in certain biomes (e.g., many coniferous trees have leaves that are less susceptible to freezing damage).
2. Thermoregulation is also worth going into in more detail. Many students are confused by the common terms "warm blooded" and "cold blooded", mistakenly believing that some animals literally have warm and cold blood. Given this common misconception, it's important to discuss the difference between ectotherms, which rely on the environment to regulate their body temperature and endotherms, which regulate their own body temperature metabolically. I like to use this distinction to draw out some prior knowledge from the students about what kinds of animals fit into either category. Most students know, for example, that reptiles are ectothermic and mammals are endothermic. I then ask what that means for geographic distribution of these animals by asking, "are there reptiles at the North Pole?". Students know that there are not, so that's a good way of pointing out that one of the major advantages of being an endotherm is an expanded geographical range compared to most ectotherms. I then ask if students have ever heard that snakes and other reptiles can survive on very little food, and most students reply that they know this, with some offering specific information they already knew (e.g., some large snakes eat once a month or less). I then ask if we can survive on very little food, and most students acknowledge that we have to eat more or less constantly to avoid feeling very hungry. This points to a major disadvantage of being an endotherm: that metabolically regulating or temperature requires a near-constant supply of food. In this way, I hope students get a sense that adaptations usually involve some kind of trade-off and it's generally not possible to declare one type of adaptation "superior" to another, it really depends on the environmental conditions of a particular place.
Following the presentation, I ask students to take out their homework assignment and refer to the tables they completed about two biomes.
I then ask them to do a short activity in their groups (3 to 4 students). I ask them to review the different adaptations from the notesheet and write down examples if they had found them in their textbook reading. I ask students to not only take note of the specific organism that has a particular adaptation (e.g., polar bears are both endothermic and use hair and body fat as insulation against the cold, providing good examples of thermoregulation), but to also note which biome(s) the adaptation can be found in (e.g, thermoregulation occurs in different ways in almost every biome).
Since each student had chosen 2 biomes to summarize, hopefully the group as a whole has enough different biomes so that each student in the group can participate in their small discussion.
After students have discussed with their groups for about 10 minutes, I ask for all students attention to the board where I have written down the adaptations we had discussed in the presentation (essentially the vocab that fills in the blank spaces on the notesheet). I then go through each adaptation one by one and ask students for examples of those adaptations. When examples are given, I ask "and which biome is that organism from?", and write down the name of the biome under the adaptation.
In this way, we collectively make a picture of how these adaptations can appear in multiple biomes, hopefully reinforcing the idea that adaptation doesn't mean invention, but rather a modification of existing structures and/or behaviors to suit different environmental conditions.