Topic: Decomposition Unit |
Grade Level: 4-5
National Science Education Standards Addressed:
- Science as inquiry (K-4) -- Content Standard A:
- Students will develop the abilities necessary to do basic scientific inquiry:
- Ask questions about objects, organisms, and events in the environment.
- Plan and conduct a simple investigation.
- Employ simple equipment and tools to gather data and extend the senses.
- Use data to construct a reasonable explanation.
- Communicate investigations and explanations.
- Students will understand basic ideas related to scientific inquiry:
- Scientific investigations involve asking and answering a question and comparing the answer with what scientists already know about the world.
- Scientists use different kinds of investigations depending on the questions they are trying to answer.
- Simple instruments provide more information than scientists can obtain using only their senses.
- Scientists develop explanations using observations and what is already known about the world; good explanations are based on evidence from investigations.
- Scientists make the results of their investigations public, describing it in a way that allows others to repeat the investigation.
- Scientists review and ask questions about the results of other scientists' work.
- Life Science (K-4) -- Content Standard C:
- Students will learn about the life cycles of organisms:
- Organisms have life cycles that include different stages. The details are different for different organisms.
- Students will learn that organisms cause changes in the environments where they live:
- All organisms cause changes in the environment where they live. Some are harmful to the organism, while others are beneficial. Humans change environments in ways that can be either beneficial or detrimental for themselves and other organisms.
- Science in Personal and Social Perspectives (K-4) -- Content Standard F:
- Students will develop an understanding of changes in environments:
- Environments are the space, conditions, and factors that affect an individual's and a population's ability to survive and their quality of life.
- Changes in environments can be natural or influenced by humans.
- Some environmental changes occur slowly, and others occur rapidly.
Concepts, Skills, Attitudes / Habits of Mind Emphasized:
Key Science Skills:
- Life Cycle Changes:
- Decomposers are a vital link in the natural cycle of life and death.
- Through decomposition, minerals and nutrients, once useful to their plant or animal hosts, are released and recycled.
- Every organism in a population has a niche in the ecosystem (producer, decomposer, consumer).
- Organisms may interact with one another in several different ways:
predator/prey, producer/consumer, parasite/host; one organism may scavenge or decompose another.
- Asking questions about objects, organisms, and events in the environment
- Planning and conducting simple investigations
- Communicating investigations and explanations
Key Science Attitudes / Habits of Mind:
- Respect for evidence and reasoning
- Interest in and respect for the natural world
Key Science Content:
- Decomposition is the natural breaking down of organic materials. It is the main way that nutrients are recycled into the soil.
- In the process of decomposition, complex molecules are reduced to simple molecules.
- The decomposition of organic matter begins with large organisms in the soil such as earthworms, beetles, and slugs. These organisms break down the
organic matter into smaller pieces that smaller organisms like fungi and bacteria can further decompose.
- As decomposers break down organic materials, they release the nutrients back to the soil to be used by the next generation of plants, and the cycle begins again. Over time, the organic materials will actually become part of the soil, enriching it in the process.
Embedded Assessment Techniques -- Tools to Assess Science Skills:
- Summary of Evidence. This is a narrative summary, written by the teacher and based on teacher observations and review of student work. It is used to evaluate students' questioning and observation skills as well as content understanding. Students' work will be collected from their individual science journals. Work reviewed will include sketches, investigation plans, data collections, observations, and questions. The teacher should look for expressions of attitudes and feelings, evidence of conceptual knowledge, indications that the student has achieved skills in using equipment, and indications that the student has carried out scientific processes.
- Scale/Rubric. Use to describe students' progress in communicating their ideas and explanations.
Materials and Resources Needed:
- science journals
- drawing, writing, and graph paper
- soil thermometers
- bug boxes
- plastic bags
- plant debris
- fruit peels
- grass clippings
- empty 2-liter bottles
- measuring cups
- other materials as requested by students
- Books (examples): GROWING ACTIVITIES FOR GROWING MINDS; BOTTLE BIOLOGY: AN IDEA BOOK FOR EXPLORING THE WORLD THROUGH PLASTIC BOTTLES AND OTHER RECYCLABLE MATERIALS; GROWING IDEAS JOURNAL; ECO-INQUIRY: A GUIDE TO ECOLOGICAL LEARNING EXPERIENCES FOR THE UPPER ELEMENTARY/MIDDLE GRADES; NATIONAL SCIENCE EDUCATION STANDARDS; ACTIVE ASSESSMENT FOR ACTIVE SCIENCE; PRIMARY SCIENCE: TAKING THE PLUNGE; IN SEARCH OF UNDERSTANDING: THE CASE FOR CONSTRUCTIVIST CLASSROOMS. Nonfiction library books related to ecology that include information on decomposers.
- People/Experts: naturalist from a state park; National Gardening Association staff member. You may of course substitute other experts.
- Web sites: Soil Organic Matter Decomposition and Nutrient Cycling
Lessons Prior to Unit:
(Lesson plan adapted from "Fungus Among Us," GROWING ACTIVITIES FOR GROWING MINDS, the National Gardening Association.)
- Week One: Work with students to gather samples of soil from schoolyard and dissect the soil -- looking for and listing ingredients. Help students to note the importance of recording location and conditions when samples are taken.
- Week Two: Work with students on sketching observations in nature and on using descriptive language. Discuss the importance of capturing detail in sketches and words. Relate this to work of naturalists.
The Teaching Cycle:
- Laying the groundwork (how to inspire interest and find out what students already know)
Objective: Students to observe and begin to understand the process of decomposition.
- Week Three/First Week of Decomposition Unit:
- Students observe that teacher has gathered decomposing materials in plastic bags. Students predict and record changes in the contents of the plastic bags (over one-week period).
- Class Discussion: How did the changes compare with predictions? Where have you noticed this kind of change before? What do you think might be causing this change? Where have you seen examples of once-living things changing and decomposing in the environment? If leaves, twigs, old plant stems, and other natural materials are constantly dying and falling to the ground, why do you think we're not buried under them?
Explain to students that the same type of changes occurring in the bags constantly occur outdoors. Once-living materials are broken down by millions of microscopic bacteria, fungi, and other decomposers.
- Prepare for field exploration by discussing some do's and don'ts of field work.
- Week Four:
- Prior to boarding the bus, prepare for field exploration. Ask: "What could we see that would tell us if decomposition is occurring? Where do you think will be the best spots to look for decomposition? When picking up samples, why might it be important not to touch the item with your bare hand? What do you think will be important information to record in your journals?"
- Using the list generated the previous week, review with students how scientists behave while doing research. (It might include: handling equipment with care, using time wisely in our outdoor classroom, not damaging plants, staying inside boundaries, not putting anything in our mouths, not throwing things or chasing animals, working quietly so as not to scare off wildlife, and not touching dead animals.)
- Students undertake field exploration to look for examples of decomposition in the environment and for signs of decomposers. (This trip could also take place after the students have set up their explorations and are waiting for results before making connections.)
- Back in the classroom: journal entries on the topic "The best part about doing field work is . . . "
- Review students' previous explorations of soil, focusing on the parts of soil and the importance of living and once-living matter in soils. Ask students: "Based on what you saw in the plastic bags and on the field exploration, how do you think microorganisms might help create more soil? How could we explore this?"
- Exploration (how questions for exploration will be chosen, investigations managed, and students grouped)
Objective: Students to understand that soil hastens decomposition of living matter, which, in turn, becomes part of the soil.
- Week Five:
- Ask: "How could we set up an investigation to examine whether soil helps once-living things decompose?"
- Students work in small groups to design investigations. You could use the Research Proposal form from ECO-INQUIRY, pages 230 and 231, as a guide. (See ECO-INQUIRY: A GUIDE TO ECOLOGICAL LEARNING EXPERIENCES FOR THE UPPER ELEMENTARY/MIDDLE GRADES, by Kathleen Hogan, Kendall/Hunt Publishing Company, 1994.)
- Students meet with teacher to discuss small-group plans.
- Whole-class discussion of plans for observation and care. Develop recording sheets. (Data collection could include measurable changes in weight, height, and temperature, and observable changes in smell and appearance.)
- Make "decomposition columns" from 2-liter bottles and materials provided -- lettuce, twigs, leaves, fruit peels, etc. (A decomposition column is like a miniature compost pile or forest floor. Through the sides of the bottle, students can observe different substances decompose.) Set up investigations.
- Students make sketches in their science journals and add recording sheets for data collection.
- Week Six, Seven, Eight, and Nine:
- Students regularly record observations of their decomposition columns. Hand lenses, scales, rulers, and soil thermometers to be made available to students during this time.
- Week Ten:
- Discuss findings: "How did the materials in each of the decomposition columns change? Why do you think there might have been differences between the models? Did some materials decompose more quickly than others? Which? Did some materials show no signs of decomposition? Which?"
Possible activities while observing decomposition columns over time:
- Examine the role of the earthworm as a decomposer. Build and maintain earthworm bins.
- Text-set go-round: students browse non-fiction books related to the investigation and chart their findings, as well as coming up with new questions.
- Students research some naturalists and scientists, looking at their record-keeping strategies and research techniques.
Making connections (how to help students make sense of investigations, communicate findings, and critically reflect on their investigation and the science process):
- Week Eleven:
- Possible discussion questions: "Why do you think the materials might break down quickly in soil? Based on your observations and experiences, what do you think happens to once-living things that decompose in the soil? How do you think these once-living materials might help support new life? What kind of materials do you think decomposers cannot break down? What do you think eventually happens to those materials?"
- Share the following information with students: as decomposers break down these organic materials, they are releasing the nutrients back to the soil to be used by the next generation of plants, and the cycle begins again. Over time, the organic materials will actually become part of the soil, enriching it in the process.
Branching out (how to help students share their new knowledge and encourage them to take action on what they've learned):
- Begin new investigations: investigate what conditions, such as moisture, temperature, and soil type, seem to promote the most rapid decomposition. Individuals and small groups can test conditions. See BOTTLE BIOLOGY: AN IDEA BOOK FOR EXPLORING THE WORLD THROUGH PLASTIC BOTTLES AND OTHER RECYCLABLE MATERIALS, by Mrill Ingram (Kendall/Hunt Publishing Company, 1994), for ideas. Give students time to set up experiments and create new data-collection sheets.
- Find out what your city or town does with materials that take a long time to decompose, and how we can reduce the amount of these materials in the environment and recycle what is already around. Visit a local landfill or invite a guest speaker to the school.
- Set up model waste systems that will help biodegradable plastic bags decompose.
- Develop a school composting program to create rich compost for a garden.