Food Chain, Decomposition
Teaching Kitchen, Classroom
5th - 8th grade
Role of Teacher
Classroom management, Curricular Tie
Summer, Early Fall
Ingredients: Tomatoes / Lemon / Chives (or red onion) / Cilantro / Parsley / Salt (to taste)
Equipment: Cutting Boards / Knives/ Bowls / Spoons / Strainers
- A food chain shows how living things rely on each other for food and how energy transfers from one living organism to another. A food web connects groups of food chains. In any given food chain there will be producers, consumers, and decomposers. Producers and consumers are living things that need each other to survive. Consumers that eat primarily plants are called herbivores, and those that eat animals are called carnivores. An omnivore eats both plants and animals.
- Organisms that feed off of dead, or non-living material, are called decomposers. Decomposers naturally break down organic material to recycle nutrients back into soil. Over time, the organic materials decomposed by fungi, bacteria, and invertebrates will become part of the soil, enriching it in the process.
- Use the acronym “FBI” to describe decomposers:
- Fungi: Fungi decompose by sending out branches of root-like hyphae to break down organic matter. Mold and mushrooms are common examples of fungi. It takes 50-100 years for fungi to break a tree trunk down into dust.
- Bacteria: Bacteria are microscopic organisms that can live anywhere and are responsible for recycling dead fungi and animal matter. Together with fungi, bacteria are responsible for 80 – 90% of forest decomposition.
- Invertebrates/Scavengers: Many invertebrates as well as scavengers, like turkey vultures and ravens, break larger dead animals and plants into smaller pieces to be decomposed by fungi and bacteria. Most insects, and other invertebrates, like worms, are largely responsible for the humus layer of the forest floor. This layer is between the freshly fallen leaves/pine needles and above the more compact and dense spoil, made up of decomposing organic matter.
- Decomposers keep ecosystems clean by breaking down dead plants and animals. Imagine if all of the leaves, pine cones and fallen trees from millions of years were still on the ground! They also recycle nutrients, changing nitrogen from the air into a form that can be absorbed by plants. Recycling nitrogen is important because it helps plants produce their food and helps animals, like us, build protein. This process is called the Nitrogen Cycle.
- Seed saving, an ancient technique of collecting the seeds after a harvest and storing them for use the following season, relies heavily on decomposers and the process of decomposition. To prepare seeds – specifically, tomato seeds – for storing, farmers and gardeners must remove the gelatinous, jelly-like coating encasing the seed. By fermenting the tomato seeds, mold and bacteria will grow and naturally break down the gelatinous coating around the seed. Afterwards, the seeds will be ready for storing and planting in the coming season.
Topics / Goals / Learning Objectives
- Describe the way energy from the sun transfers within a food chain between producers, consumers, and decomposers
- Explore how all living things depend directly or indirectly on green plants to survive
- Introduce seed saving as a technique to repopulate producers in your school garden ecosystem
- Identify 3 types of decomposers – fungus, bacteria, invertebrates
- Make Garden Harvest Salsa
Opening / hook
Welcome to the Teaching Kitchen, students! Like scientists, we will investigate how energy flows through a food chain – beginning with energy from the sun, moving through producers and consumers. If we think of our Teaching Kitchen as an ecosystem, what living organisms live here? There was some producers – the plants, and the fruit at our stations were once connected to green plants – and we are consumers; the people in this room will eat the plants to survive.
What happens to all the organic material that we don’t directly consume? Or what if we forgot to eat the bread in the pantry? Mold and bacteria would grow to naturally break down the bread in a process called decomposition; and we can call the mold and bacteria our decomposers.
To investigate just how decomposers begin their process to break down organic material, we are going to harvest tomatoes from the garden and collect the seeds for saving. We save the seeds to grow a new harvest next season, to ensure that we – the consumers of our classroom ecosystem – have energy to sustain ourselves.
Procedures / Activities
- Each table will collect seeds for saving and prepare their own garden harvest salsa recipe. Each student will need a cutting board, knife, and spoon.
- Split the following ingredients between each team of students: tomatoes for dicing, chives for mincing, cilantro for plucking, and a lemon for squeezing.
- Each team of students will also need a bowl to combine their salsa recipe and a separate bowl to collect their tomatoe seeds for saving.
- Welcome students into the kitchen and have them wash hands.
- Introduce lesson with a review of energy transfer and the food chain.
- Remind students of proper knife skills (i.e. “bear claw” while cutting vegetables) and review the terms “dice” and “mince” in reference to the tomato and chives, respectively.
- Have students collect some tomato seeds in a bowl while preparing their garden harvest salsa. In a separate bowl, students combine their vegetables. Stir to evenly incorporate all ingredients. Add salt to taste.
- After every group finishes their prep, the teacher leads the class in the science-based curricular tie. Specifically, the teacher explains that while first and foremost the class is storing seeds to ensure a harvest for the coming seasons, seed saving also demonstrates decomposition in real time.
- Collect the student’s bowls of seed savings. If a collection of seeds has already been fermented, the teacher can circulate it around the classroom and ask students to volunteer observations they made about the seeds. Ask: “What decomposers are present in this seed saving biome?”
- Clear the tables of extra materials, and allow students to taste their recipe with tortilla chips.
End with a tasting and allow students to make “scientific observations” about the sight, smell, and taste of their garden harvest salsa.
Extensions / Adaptations / Games
- As a class, brainstorm experiments to determine the best conditions for bacteria growth within your seed saving biomes. Predict what would happen if you expose some team’s collection bowls to light, or refrigerated them?
Resource on Food Chain & Decomposition: BrainPop Video
Abridged Original Lesson Plan: Dirty Classroom Forum
Reference EcoSpaces lesson on Seed Saving: EcoSpaces Education
Recipe: Garden Harvest Salsa Recipe Card