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Transcript
Extension to PLT Activity 24 Nature’s Recyclers Lesson Summary The original version of Nature’s Recyclers teaches students about the process of decomposition by observing pill bug, sow bug, or earthworm behavior. This extension to Nature’s Recyclers places emphasis on the importance of decomposers in a healthy forest ecosystem. It draws students’ attention to decomposing organisms that are not often noticed, such as fungi and bacteria. d. What are other examples of decomposing organisms? Decomposers are abundant in our ecosystem and likely outnumber all other groups of organisms in diversity and quantity. But many of these organisms are unfamiliar to us because they are either microscopic (Figure 8) or hidden deep in the soil or within plants and animals. These may include insects such as beetle grubs or fly maggots, numerous fungi, and countless bacteria. Illustration: Geetha S. Iyer Doing the Activity 1. Read the original Nature’s Recyclers on page 108 of the PLT Activity Guide, including the Background Information, Getting Ready, and Doing the Activity sections. 2. This extension builds on the wrap-up question in step 9 of Doing the Activity, “How might sow or pill bugs be important to a forest ecosystem?” Make sure to touch upon the following questions in an expanded discussion on the role of decomposers in an ecosystem. a. What is an ecosystem service? An ecosystem service is a vital function that some organisms in the ecosystem provide for the benefit of all the others. For instance, plants produce oxygen that other animals need to survive. Decomposition is another ecosystem service that organisms such as pill bugs and sow bugs provide. If they didn’t exist, dead matter would pile up on the forest floor, and all the nutrients locked within that matter would not be recycled back into the ecosystem. b. Do decomposers obtain their food by killing organisms? No, most decomposers are not responsible for killing an organism. For instance, decomposers that specialize on dead plant matter usually don’t eat living plants—they are not herbivores. Similarly, decomposers don’t hunt down living animals like carnivores do; they consume and break down dead animal tissues instead. Figure 8. Tiny titans: Most decomposing organisms are microscopic, but they have an immense impact on ecosystem health. Clockwise from top left: nematode, amoeba, filaments of a fungus, and soil bacteria. 3. Wrap up the discussion by telling students that while decomposers such as insects and fungi do not kill organisms, other insects and fungi certainly can. Ask students to contemplate whether organisms that could damage, disease, or kill trees are essentially good or bad for the ecosystem. Can they be both? Impress upon students the important roles of all organisms in a healthy ecosystem—when some organisms die, others profit. This process is cyclic. For instance, the nutrients released by decomposition of an old tree may favor the growth of seeds that the tree produced before it died. c. What sorts of waste can students imagine finding in a forest? Leaf litter; pieces of fallen bark; dead trees; dead animals; cast-off skins of animals that molt, such as snakes or cicadas; empty egg shells; animal droppings; and fallen fruit are among the dead matter that may be found in a forest. 20 What Is a Healthy Forest | Section 1 | Forests as Ecosystems