Introduction
The natural world is my passion, and as a teacher, sharing it with my students is my gift to them. I spent summers backpacking for a week at a time with my family beginning at the early age of three months. I spent time swimming in lakes, reading books in the hammock, and gathering kindling for the evening's fire that would keep us warm. I learned to appreciate the red thimbleberries that grew in the dark forests. I remember learning about birds that also liked eating these berries, and how this helped the berry-bushes reproduce because the birds scattered seeds in the forest. I learned many valuable life lessons in the great outdoors, and I always felt a renewed appreciation for the basics of food, water, and shelter.
Many students are curious and respectful of nature. Some collect pill bugs and other small insects in plastic bottles to examine and share them with classmates; maybe these students will become future entomologists. But other students smash the life out of insects, and I will never forget the day that I euthanized a mealworm that had a small hole poked in it from a student's pencil. I want students to respect all life-forms, and to understand how they continually evolve in response to the environment. By grasping this idea, I believe that they will gain a better appreciation for the environment, all living creatures, and themselves.
Life science teaching for my second grade students has included raising mealworms and plants, and learning about adaptations as structures that have a purpose. While this is a good starting place for life sciences in the second grade it has always seemed simplistic to me. Adaptations indicate that an organism has changed in some way to better match its environment. If an organism has changed, what was there before the change arose? This unit is about answering two essential questions: How do organisms adapt? And why do organisms adapt? I will teach my students about evolution through observations, comparisons and games so that they better understand how adaptations cause organisms to differ from one another, and how this explains the biodiversity of life.
Objectives
In this unit, students will understand evolution by learning that 1) traits that improve a species match to their environment will be selected and passed onto their offspring, 2) traits that improve the fit to the environment are called adaptations, 3) adaptations arise from already existing material, and 4) all of life evolved.
To help clarify the often misunderstood topic of evolutionary biology, the background of this unit includes information about natural selection, a process which explains how and why adaptation occurs. I also explain what speciation is, and how it explains how different species arise. While speciation is not taught in my unit, I think it is important for teachers to understand and you may choose to foreshadow the idea for learners in your class who may be ready to grasp this concept. The fossil record is invaluable to the study of evolution and so I will also include this in my background information. Why Evolution is True by Jerry A. Coyne is an excellent book that is clearly written and includes diagrams and photographs of the fossil record.
While much of the emphasis in teaching focuses on getting the "right answers" this unit will value curiosity and questioning as essential for creating the next science literate generation. Stuart Firestein writes in his book Ignorance How it Drives Science, "Too much emphasis on the answers and too little attention to the questions have produced a warped view of science. And this is a pity, because it is the questions that make science such a fun game." Students will sketch, label, and write about what they notice and what they wonder. Asking questions is one of eight essential elements of the K-12 science and engineering curriculum from the new Framework for K-12 Science Education.
Students will compare and contrast the dragonfly from the order of Odonata with the house fly from the order of Diptera. I will guide the students in understanding how a physical adaptation arises from already existing material by focusing on two adaptations in these insects: the mouthparts and wings. Students will build a model of the dragonfly's mouthparts and the fly's proboscis. Building models is an essential practice for K-12 science and engineering curriculum in the new Framework for K-12 Science Education. All models are good for teaching some things but not others, and we will discuss how models help scientists think about the natural world. Students will participate in a game that shows how adaptations that are beneficial will increase in a population and thus learn about natural selection.
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