Why are Decomposers Important?

33 teachers like this lesson
Print Lesson


SWBAT explain the importance of decomposers in an ecosystem.

Big Idea

In this lesson, students will learn about the role of decomposers through the use of teacher posters, video clips, and moldy visual aids. Then, students will summarize their learning by writing a paragraph on the importance of decomposers.

Lesson Overview

Inquiry Based Instructional Model

To intertwine scientific knowledge and practices and to empower students to learn through exploration, it is essential for scientific inquiry to be embedded in science education. While there are many types of inquiry-based models, one model that I've grown to appreciate and use is called the FERA Learning Cycle, developed by the National Science Resources Center (NSRC):

1. Focus

2. Explore

3. Reflect

4. Apply

A framework for implementation can be found here

I absolutely love how the Center for Inquiry Science at the Institute for Systems Biology explains that this is "not a locked-step method" but "rather a cyclical process," meaning that some lessons may start off at the focus phase while others may begin at the explore phase. 

Finally, an amazing article found at Edudemic.com, How Inquiry-Based Learning Works with STEMvery clearly outlines how inquiry based learning "paves the way for effective learning in science" and supports College and Career Readiness, particularly in the area of STEM career choices. 

Unit Explanation

In this unit, students will first develop an understanding of the biotic and abiotic factors within ecosystems, the characteristics and classification of living organisms, and how plants and animals obtain and use energy to fulfill their needs. 

Then, students will delve deeper into the NGSS standards by examining the interdependent relationships within an ecosystem by studying movement of matter between producers, consumers, and decomposers by creating models of food chains and food webs.  

At the end of this unit, students will study ways that individual communities can use science ideas to protect the Earth's resources and environment.  

Summary of Lesson

Today, I will open the lesson by discussing the roles of producers, consumers, and decomposers within an ecosystem. Students will then investigate the importance of decomposers by watching a video and taking notes on presented information. At the end of the lesson, students will reflect and apply their new understanding of decomposers by writing a summary.

Next Generation Science Standards  

This lesson will support the following NGSS Standard(s):

5-PS3-1.    Use models to describe that energy in animals’ food (used for body repair, growth, motion, and to maintain body warmth) was once energy from the sun.  

5-LS1-1.    Support an argument that plants get the materials they need for growth chiefly from air and water.  

5-LS2-1.    Develop a model to describe the movement of matter among plants, animals, decomposers, and the environment.  

Scientific & Engineering Practices

For this lesson, students are engaged in the following Science & Engineering Practice:

Science & Engineering Practice 8: Obtaining, Evaluating, and Communicating Information -

Students will combine information from videos, visual aids, and a teacher presentation to obtain ideas and describe how they are supported by evidence. Later on, the will communicate this information by writing and sharing summaries.

Crosscutting Concepts

To relate ideas across disciplinary content, during this lesson I focus on the following Crosscutting Concept

Crosscutting Concept 1: Patterns 

Students will classify information on decomposers and will identity relationships between producers, consumers, and decomposers.  

Disciplinary Core Ideas

In addition, this lesson also aligns with the following Disciplinary Core Ideas

PS3.D:  Energy in Chemical Processes and Everyday Life

The energy released [from] food was once energy from the sun that was captured by plants in the chemical process that forms plant matter (from air and water). (5-PS3-1)

LS1.C:  Organization for Matter and Energy Flow in Organisms

Food provides animals with the materials they need for body repair and growth and the energy they need to maintain body warmth and for motion. (secondary to 5-PS3-1)

Plants acquire their material for growth chiefly from air and water. (5-LS1-1)

LS2.A:  Interdependent Relationships in Ecosystems

The food of almost any kind of animal can be traced back to plants. Organisms are related in food webs in which some animals eat plants for food and other animals eat the animals that eat plants. Some organisms, such as fungi and bacteria, break down dead organisms (both plants or plants parts and animals) and therefore operate as “decomposers.” Decomposition eventually restores (recycles) some materials back to the soil. Organisms can survive only in environments in which their particular needs are met. A healthy ecosystem is one in which multiple species of different types are each able to meet their needs in a relatively stable web of life. Newly introduced species can damage the balance of an ecosystem. (5-LS2-1)

LS2.B:  Cycles of Matter and Energy Transfer in Ecosystems

Matter cycles between the air and soil and among plants, animals, and microbes as these organisms live and die. Organisms obtain gases, and water, from the environment, and release waste matter (gas, liquid, or solid) back into the environment. (5-LS2-1)

Choosing Science Teams

With science, it is often difficult to find a balance between providing students with as many hands-on experiences as possible, having plenty of science materials, and offering students a collaborative setting to solve problems. Any time groups have four or more students, the opportunities for individual students to speak and take part in the exploration process decreases. With groups of two, I often struggle to find enough science materials to go around. So this year, I chose to place students in teams of three! Picking science teams is always easy as I already have students placed in desk groups based upon behavior, abilities, and communication skills. Each desk group has about six kids, so I simply divide this larger group in half. 

Gathering Supplies & Assigning Roles

To encourage a smooth running classroom, I ask students to decide who is a 1, 2, or 3 in their groups of three students (without talking). In no time, each student has a number in the air. I'll then ask the "threes" to get certain supplies, "ones" to grab their computers, and "twos" to hand out papers (or whatever is needed for the lesson). This management strategy has proven to be effective when cleaning up and returning supplies as well!  


10 minutes

Lesson Introduction & Goal 

I introduce today's learning goal: I can explain the importance of decomposers in an ecosystem. 


I want to inspire interest in today's lesson and capitalize on student curiosity, so I begin by holding up a Moldy Apple. As I walk around the classroom with the moldy apple, I ask: Has anyone ever seen mold growing on food in your refrigerator? I then point out some mold in one of the team's ecocolumns: Mold in an Ecocolumn! Students are immediately interested and grossed out the same time! One student tells us about a time he almost ate mold!

Next, I showed students the following video. Again, students were so interested in the "gross" process of decomposition.

Roles in Ecosystem Poster

To help students organize the relationships between producers, consumers, and decomposers, I construct the following poster alongside of students, with student input: Roles in Ecosystems Poster. Prior to today's lesson, I drew the Producer (grass), Consumer (rabbit), and Decomposers (fungi and bacteria) on the poster to save time by simply projecting and sketching clipart from the internet.

During this poster-making time, students participate by sharing their thinking and by taking notes in their journals: Student Notes.

Teacher Note: When anchor charts, such as the Roles in Ecosystems Poster above, are created with students present, the students are able to contribute ideas and are much more likely to take ownership of the poster. Consequently, during later lessons, more students will proudly refer to this poster to recall key information or words. 

Also, I use posters often as it provides students with both a language and visual reference. One of the best ways to support my ELL learners is to provide a language rich environment using graphic organizers and color-categorizing. 


I begin by explaining how producers get their energy. Although my students have learned about producers, plants capturing the sun's energy, and photosynthesis, this poster presents a great opportunity to review these concepts once more. I find that revisiting major concepts often helps students develop a deeper understanding. 


Next, we move on to consumers. We discuss the fact that the sun's energy is passed on when the rabbit eats the grass. We then talk about the fact that consumers have to eat other animals or plants for energy (and survival).


Finally, we discuss how the sun's energy is passed on from the rabbit and the grass to the decomposers when the rabbit and grass dies. The decomposers (fungi and bacteria) help break down dead organisms and return (recycle) nutrients back to the soil for new plants. 

The light bulbs went ON and I heard students say, "Oh! Now I get!" and "That's makes so much sense!" 


To promote student thinking about this cycle of energy, I simply ask students to share their observations. I write the first letter of each student's name and their observation along the side of the poster: Student Observations. Students also take these notes in their journals: Student Notes on Observations.

I love listening to the students make important connections, such as, "If there's something wrong with the producers, everything can go wrong in the food chain." 

To wrap of student thinking, I wrote at the top (under the title): So... "All organisms in the food chain need what to survive? The sun's energy! 


30 minutes


At this point, I wanted to provide students with the opportunity to explore the importance of decomposers further by watching the following video. To focus on the most relevant information, I played the video until 7:00 minutes, continued at 8:30 minutes, and stopped at 13:30 minutes. I invite students to take notes in their journals during this time as well (Student Notes on Decomposers).

Decomposers Poster

Throughout the video, I press pause and discuss major concepts with students. I also model how to organize ideas by creating an idea web on another poster: Decomposers Poster. We first discuss the meaning and roles of decomposers. 

I feel it is really important to discuss how scavengers also play an important role in the decomposition process. The video perfectly highlights how large scavengers, small scavengers, and decomposers work together to break organic matter down. We will return to this poster tomorrow to review the decomposition process and to identify specify type of bacteria and fungi. 

Paragraph Summary

Following the video and notes, I want to provide students with an opportunity to summarize their learning, so I pass out the following graphic organizer. I have to say that this is one of the best graphic organizers that I've come across that supports paragraph structure and the development of an evidence-based argument. I ask all students to begin with the same topic sentence: Decomposers are a very important part of an ecosystem. I also provide students a conclusion sentence prompt: As you can see... 

Monitoring Student Understanding

Once students begin working, I conference with every group. My goal is to support students by asking guiding questions (listed below). I also want to encourage students to engage in Science & Engineering Practice 7: Engaging in Argument from Evidence

  1. What patterns have you noticed? 
  2. Why do you suppose ____? 
  3. What have you found so far? 
  4. Has your thinking changed? 
  5. What evidence do you have? 
  6. How did you decide _____?
  7. What conclusion can you draw about ____?
  8. Do your details support the main idea? 

Student Conferences

During this conference, Supporting the Main Idea, I encourage students to think about how their details support the main idea. In the process of teaching science concepts, I'm also able to support ELA standards, such as, CCSS.ELA-Literacy.W.5.2.B: Develop the topic with facts, definitions, concrete details, quotations, or other information and examples related to the topic.

Here, Making Connections with Student Lives, I try to make these abstract science concepts more meaningful by asking students about their own personal experiences. I think this also helps students link new information with prior knowledge. 

Student Work

Here are a few examples of student work during this time. Almost all students were successful at this activity! 

Reflect & Apply

20 minutes

Sharing Findings

Now that students have built meaning and understanding by observing, exploring, and summarizing their thinking, it is important to provide students with the opportunity to share their findings. For this reason, I invite students to read their team's paragraphs aloud. As students share, I engage the other students by asking, "Do you agree?" "Does that detail support the main idea?" 


Looking Back

Today was my first experience using this graphic organizer to help students summarize their learning. I loved the main idea, supporting detail, and conclusion boxes as they helped students organize their thinking and learning! This turned out to be the perfect way for students to review why decomposers are so important. 

During upcoming lessons, we will circle back to the Decomposers Poster in order to continually review key concepts and to ensure students really understand the role of decomposers in ecosystems.