Lesson A4: Producers, Consumers, and Decomposers

Key Ideas   Unit Checklist

  Video Lesson

Watch the following video to see some interesting examples of producers, consumers, and decomposers.

  Lesson A4: Producers, Consumers, and Decomposers

A Web of Life

It doesn’t know it, but the loon chick has another job besides living. It has a role in its ecosystem. The loon chick fits into a large web of interacting organisms. By observing organisms over time, we understand clues about how this web works.

For example, the baby loon captures and eats a small frog. The next day, a weasel kills the baby loon and eats most of it. A magpie sees the commotion and swoops in to pick over the bird’s carcass. Within days, blowfly larvae begin to break down what is left. Eventually, no sign remains of the loon chick. Everything remaining has decomposed into soil nutrients.
Reading and Materials for This Lesson

Science in Action 7
Reading: Pages 26–34

Materials:
No other materials are needed for this lesson.

A few years later, an aspen tree sapling sprouts in the nutrient-rich soil. A few years after that, a moose calf nibbles on the tree’s leaves.

Eventually, a great cycle of who eats whom emerges from this picture. The loon chick is one part of a complex web of interconnected organisms. You might not know at first glance that the loon is connected to the frog, the weasel, the magpie, the blowfly, the aspen, and the moose. All their lives are interconnected.

Organisms in ecosystems have roles, or jobs, to do. Organisms fill the roles of producer, consumer, decomposer, and scavenger. What role does the loon chick have? What about the blowfly larvae? Or the magpie? How about the aspen sapling? Think about these kinds of roles as you explore this lesson.
Figure A.2.4.1 – A moose calf nibbles on sapling tree leaves.

Figure A.2.4.2 – A loon chick rides on its mother’s back.
Figure A.2.4.3  -  Loons live on Canadian lakes, and are prey for pikes, weasels, and coyotes.

Life Underground

If you want tasty vegetables from your garden, you need to start with good soil. Have you ever wondered what is in soil?

Soil is a mixture of minerals, water, air, decomposed leaves (leaf litter), and other dead matter. It also is home to countless organisms. Think of soil as an underground recycling centre where dead leaves and waste go in and plant nutrients come out. This centre has a lot of workers. Even a teaspoon of soil holds more than a million organisms! This makes soil the most abundant ecosystem on Earth.

What kinds of organisms live in soil? Some soil organisms are large enough to see. Earthworms, beetles, and ants live in soil.

If you look a bit closer, you can see smaller organisms such as nematodes and mites.

To look closer still, you need a microscope. Now, you can see tiny one-celled organisms such as bacteria. Soil is teeming with microscopic life.

Figure A.2.4.4 – Most earthworms feed on dead plant material in soil.
Figure A.2.4.5 – Ground beetles eat grubs, earthworms, slugs, and nematodes in the soil.

Figure A.2.4.6 – This soil mite is only one millimetre long. It feeds on dead plants and fungi in the soil.
Figure A.2.4.7 – Nematodes spend their lives foraging in soil.

 Watch More

Soil Life

This video shows you some of these odd organisms.

Producers, Consumers, and Decomposers in Forest Soil

In the forest, trees use the Sun’s energy to grow and produce leaves. Trees are producers in the soil ecosystem but not when they are living. This ecosystem relies on plant material that is dead. Few organisms in soil eat living plant material. Instead, they focus on dead leaf litter and twigs. The tiny bacteria and one-celled organisms that consume this material are primary consumers. By consuming dead material, bacteria help it decompose. They have a second role of decomposer. This is the real recycling job.

Dead material is broken down into nutrients. Imagine what the forest would be like if no one did this job! Eventually, dead material would stack up everywhere. Without nutrients, the trees and other plants would weaken and die. Then, every other organism would die due to lack of food.

Nematodes consume the bacteria and one-celled organisms. They are secondary consumers. Beetles are higher-level consumers in the soil ecosystem. They eat nematodes.

By crawling and wriggling through soil, larger organisms such as beetles and earthworms till the soil. They work air into it that plant roots need. They shred dead material and help mix it into the soil so that nutrients are spread evenly. The soil ecosystem works continuously to make useful soil for the trees and other plants of the forest. This is an amazing nutrient recycling system. The next time you take a walk in the forest, imagine the busy nutrient factory under your feet.
Figure A.2.4.8 – Trees rely on soil nutrients to grow.

Figure A.2.4.9 – In autumn, soil organisms begin breaking down fallen leaves and twigs.
Figure A.2.4.10 – In the spring, new growth emerges from nutrient-rich soil.

 Watch More

The Importance of Soil

Explore the importance of the soil ecosystem in this video. Many of our activities abuse soil. We must take care of it.

  Lesson Activity

Alberta Wetland Investigation

This task is a lot like conducting a crime scene investigation. Various organisms are your suspects. Instead of connecting lines of evidence, you will connect organisms. Instead of recreating the crime, you will develop a diagram of interactions.

You will use various species information websites to build your evidence. When you are done, you will have a diagram of how an Alberta wetland works.

Wetland Organisms to Investigate:


Instructions:

    1. In addition to the animals listed above, your diagram must contain plants. You will add algae, grass, and aspen trees.

    2. Open a word document on your computer, or have pen and paper ready so you can take notes as you go.

    3. Visit each web page listed above. Read carefully each organism profile. Make notes of what that organism eats and who eats it.

    4. Consider the notes you have made. What food connections do you notice between your organisms? Make notes on your observations.

    5. Make a diagram of the food connections you discovered. Use all the organisms on the list if you can. You might find more than one way to draw your diagram. You might find that you have more than one chain of linked organisms. Those chains might link to each other. Follow the evidence, and think of this task as a puzzle. Use arrows such as those shown here. Your diagram might look something like this:

      Organism A → Organism B → Organism C → Organism D

      Organism B eats Organism A. Organism C eats Organism B – and so on.

    6. You might discover that an organism is eaten by two organisms. If so, place an arrow like this:

      Organism A → Organism B → Organism C → Organism D
                            ↑  
                   Organism E

      This means that Organism B eats both A and E.

    7. Label each organism as either a producer, a decomposer, or a consumer. You can label your consumers as primary, secondary, or higher level consumer. Use this website (http://www.enchantedlearning.com/subjects/foodchain/) to review consumer levels.

      Examine your diagram carefully. Observe the connection that each arrow represents. Does your diagram look like a chain of connections? Does it look like a connected web?
Questions:

Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.

This is one way to draw your diagram. All organisms are used, and more than one linked chain of organisms exists. In several places, the chains connect to each other. Producers are labelled P and consumers are labelled C. Numbers indicate the level of consumer. Decomposers are labelled D and scavengers are labelled Sc.


Many organisms have multiple roles. The adult female mosquito sucks blood from the lynx and beaver. It can be a level 2, 3, 5, or 6 consumer depending on its victim. The lynx can be a level 2, 4, or 5 consumer, depending on what it eats. It can also be a scavenger when it eats dead animals. The snail consumes both algae and dead material in the pond, so it has the role of primary (C1) consumer as well as decomposer.

In some organisms, roles change as they mature. Mosquito larvae are primary consumers. They graze on algae. Only the adult female consumes blood. It does not eat the whole animal. It is a special type of consumer called a parasite. The dragonfly and the frog eat different organisms when they mature, but both remain the same level consumer.

Don’t worry if you missed some relationships. The point here is to show you how diverse organism interactions can be. They form a complex interconnected web. By mapping the relationships and roles of organisms in an ecosystem, we obtain a good idea of how it works and how complex it is. In fact, this complexity is a sign of a very healthy ecosystem. Ecosystems with only a few organisms are vulnerable. If just one organism disappears, the whole system can collapse.
Each connection indicates who eats whom in this ecosystem. The diagram describes how organisms interact with each other based on what or who they eat. Some organisms have multiple roles, depending on their circumstances. Others change roles as they mature.
Organisms consume food for energy. The arrows indicate the directions that energy flows through the ecosystem. The arrows indicate where the energy goes, so they always point to the organism that gains the energy. Energy flows from the producer to primary, then secondary, and then higher-level consumers. Energy always flows from producers to consumers in every food chain.
The chains start with algae, grass, and aspen trees. These plants are producers. No arrows point to them. They do not eat other organisms (because they are plants).
Producers harness energy from the Sun and absorb carbon dioxide from the air to make food for themselves and for other organisms.
Likely, the lynx and the garter snake are at the tops of your chains. However, if you read the second website link for the garter snake information, you will find that several species eat it. In nature, therefore, it is not at the top of its chain. If you read the lynx website link, you will find that it has no known predators. It is at the top of its chain in nature.
Snails, mosquitoes, and beaver would starve if the producers disappeared because they would have no food to eat. Then, higher level consumers would die because they would also have no food.
Yes, the snail eats algae as well as dead plant material according to second website link for it. As a decomposer, it recycles nutrients in the ecosystem.
Yes, the lynx sometimes will scavenge dead animals such as a deer killed by another animal. By consuming dead animals, scavengers help recycle nutrients.



  Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to guide your learning.

Unit A Lesson 4 Self-Check

Instructions


Complete the following 6 steps. Don't skip steps – if you do them in order, you will confirm your understanding of this lesson and create a study bank for the future.

  1. DOWNLOAD the self-check quiz by clicking here.

  2. ANSWER all the questions on the downloaded quiz in the spaces provided. Think carefully before typing your answers. Review this lesson if you need to. Save your quiz when you are done.

  3. COMPARE your answers with the suggested "Self-Check Quiz Answers" below. WAIT! You didn't skip step 2, did you? It's very important to carefully write out your own answers before checking the suggested answers.

  4. REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct any mistakes you made. This will make your self-check quiz an excellent study tool you can use later.

  5. SAVE your quiz to a folder on your computer, or to your Private Files. That way you will know where it is for later studying.

  6. CHECK with your teacher if you need to. If after completing all these steps you are still not sure about the questions or your answers, you should ask for more feedback from your teacher. To do this, post in the Course Questions Forum, or send your teacher an email. In either case, attach your completed quiz and ask; "Can you look at this quiz and give me some feedback please?" They will be happy to help you!


Self-Check Time!
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Self-Check Quiz Answers

Click each of the suggested answers below, and carefully compare your answers to the suggested answers.

If you have not done the quiz yet – STOP – and go back to step 1 above. Do not look at the answers without first trying the questions.

Producers make their own food by harnessing the Sun’s energy and absorbing carbon dioxide from the air. Plants produce food for other organisms when the organisms eat them. An example from a lake or pond is algae. An example from the ocean is phytoplankton. An example from land is grass.
Consumers eat producers or other consumers in an ecosystem. An example of a primary consumer is a rabbit. It eats plants, which are producers. A primary consumer, similar to the rabbit, is also called a herbivore. An example of a secondary consumer is a lynx. It eats mostly rabbits, so it eats primary consumers. Secondary and higher level consumers also are called carnivores because they eat meat.
These fungi consume dead matter as do all decomposers. By consuming it, they recycle the matter into nutrients. Nutrients in the soil help producers grow.
The flesh fly and its maggots are examples of scavengers., which are very important to the ecosystem. Without scavengers, dead bodies and feces would take a very long time to weather into nutrients that plants can use. Scavengers break down dead matter quickly. They make the task of decomposers much easier. Although both scavengers and decomposers work to recycle nutrients, scavengers tend to be larger than decomposers. One way to distinguish the two types of organism is by teeth. Scavengers eat their food with teeth. Decomposers excrete enzymes on the dead material to digest it.
This ecosystem is simple, but each organism has a specific role. Each role is essential. If a role is missing from an ecosystem, the system becomes unbalanced. It no longer functions because the cycle is broken.

For example, if the owl disappeared, nothing would eat the rabbits. The rabbit population would increase. Eventually, all the plants would be eaten. Then, the rabbits would starve.