GO IN DEPTH

Cycle of Life 2: Food Webs

What You Need

Materials

  • Computer and overhead projector
  • Plastic 2 liter bottles with holes in the lids and in the bottles
  • Magnifying glasses
  • Resealable plastic bags
  • Wide-mouthed jars and funnels
  • White coffee filters
  • Goose-necked reading lamp
 
Cycle of Life 2: Food Webs

Purpose

To help students understand that some insects depend on dead plant material for food and they interact with other organisms in various ways.


Context

This lesson is the second of a two-part series on the cycle of life. This series should help enhance student understanding of the flow of matter and energy and the interdependence of life by focusing on food chains and food webs.

Cycle of Life 1: Food Chains focuses on the food chain by helping students understand that almost all kinds of animals’ food can be traced back to plants and that the sun is often the ultimate source of energy needed for all organisms to stay alive and grow.

This lesson gives students the opportunity to learn about food chains. Learning about a variety of food chains in various environments will help students learn to identify similarities and differences among them. For example, they will learn that materials can be recycled and used again, sometimes in different forms. Also, they will notice that substances may change form and move from place to place, but they never appear out of nowhere and never just disappear. It is important to note that although this lesson focuses on food chains of what eats what in various environments, it does not focus on labeling the steps in the chain as energy transfer. Transfers of energy at this level are better illustrated in physical systems; biological energy transfer is far too complicated.

Cycle of Life 2: Food Webs extends this thinking by focusing on how some insects depend on dead plant matter for food and incorporates ideas previously learned about food chains and food webs.

Students will explore how various organisms satisfy their needs in the environments in which they are typically found. In addition, they will examine the survival needs of different organisms and consider how the conditions in particular habitats can limit what kinds of living things can survive. These activities will help students understand the great diversity of life in different habitats.

Students finishing the second grade should understand that plants and animals need water to survive. In addition, they should know that animals need food to survive while plants need light. They also should understand that animals eat plants or other animals for food, and animals may also use plants (or even other animals) for shelter and nesting.

This prerequisite knowledge will help elementary students expand their knowledge to learn that almost all kinds of animals’ food can be traced back to plants and that some source of energy is needed for all organisms to stay alive and grow. They also should be able to expand their knowledge to learn that insects and various other organisms depend on dead plant material for food.


Planning Ahead

Note: If items are not easily available from the school’s science department, have students bring in one or all the items except the lamp (students can share the lamp(s) if necessary). They should probably have all items to you a week prior to the activity to make sure all items are available.


Motivation

Students should use their Insects in Their Environment student esheet to go to Insects on the ThinkQuest website to read an excellent but brief description of insects.

Now students should use their student esheet to watch part of the interactive slideshow Let’s Talk about Insects, on the Urban Programs Resource Network website. (Note: The link listed will take students to slide 35; they should view only slides 35-43.)

Pose the following questions to students to stimulate their thinking about insects, the food they eat, and the environment in which they are typically found. These questions are intended to get students thinking for a project in the Development section, thus you do not need to have students write down their answers.

  • Do you think that each type of insect plays a specific role in its environment?
  • Do you think that you could move an insect that typically lives in a warm environment to a cold environment and expect that it would survive?
  • Do you think that there are other insects besides ants and termites that depend on dead plants for food?
  • Do you think that the extinction of a specific type of insect would upset the ecosystem?
  • Do you think that each type of insect is beneficial to our environment?

    Answers will vary. Encourage students to explain their answers.

Development

In this part of the lesson, students will explore insects by doing a hands-on activity and conducting some research.

Have students do the exploration activity below. Hand out the Insect Explorers activity sheet and the Insect Explorers record sheet. (This activity is adapted from the Berlese Funnel activity from Family Fun and the Dead and Alive activity from the Illinois Natural History Survey site.)

Students will explore what types of insects live under, on, and around dead trees! If there is an area on the school grounds, this can be done as a classroom activity. If not, have students do this activity outside of school in groups or individually with parents. If students do this activity outside of school, they can use the activity sheet to help guide them and their parents (you may want to provide a letter home to parents to explain what is expected of their children).

Have students roll over a rotting log to observe the variety of insects (and other creatures) that live here. They should write down the types of insects they see on their Insect Explorers record sheets. If there are insects they see but they don’t know what they are, have them coax the insects into their plastic bottle with their pen/pencil so they can do an Internet search (at school or home) to determine what type of insect they have captured. They are likely to see slow-moving pill bugs, sow bugs, slugs, snails, and earthworms; and faster-moving daddy longlegs, millipedes, centipedes, crickets, and click beetles; and maybe even bright-colored newts and salamanders! Point out that the dead logs also may host tiny seedlings, mosses and lichens, mushrooms, and other fungi.

It would be great to point out that the log encompasses the entire cycle of life: the dead tree provides food and a home for insects, creatures, and plants that, in turn, help the tree to decompose into soil from which new trees will grow. At this point, have students write down other things they notice about the log and a standing dead tree if one is around (e.g., number of holes, sizes of holes, or other animals that may have inhabited the tree like birds or squirrels).

When students are done with their investigation, have them roll the log back where they found it.

Next, have students gather some leaves and other debris anywhere around the perimeter of the rotting tree and have them put their collection (called litter) in a resealable bag, leaving the bag slightly open for air. At school/home, students can set up a device known as a berlese funnel to coax the insects from the litter. Students can use their Insect Explorers activity sheet to help them.

Have them place an open coffee filter in the bottom of a wide-mouthed jar and set a plastic funnel into the top. Pack the funnel with the leaf litter and place a goose-necked reading lamp directly over the funnel, with the bulb close to the leaves. As the lamp heats up, the insects will evacuate their hiding spots, dropping down through the funnel and into the cooler climate below. The filter paper in the bottom of the jar will help you to see the tiny creatures. When they are done, let the insects go outdoors.

Next, have students do an Internet search to determine the name of any insects they can't identify that they found under the dead log. They can record this information on their record sheet.

Last, have students select an insect that feeds off dead trees/debris. Using the Insects in Their Environment student esheet, students should get a picture of their insect and do some research on it using the Insect Explorers research sheet as a guide. Some sites on insects that may be helpful are:

Students should present their research to the class.


Assessment

Students should write a paragraph or two regarding how insects and other organisms depend on dead plant and animal material for food and how they interact with one another. Their writing sample should include information such as:

  • Trees eventually die, and then fall down.
  • Insects, animals, and bacteria that feed and live off dead trees inhabit the trees and continue to live in them as they fall down and decay.
  • On the ground, once a dead tree becomes hollow, it might become a home for animals, such as a den of rabbits or foxes.
  • Insects have both positive and negative roles in an environment.

Extensions

Bugfood III: Insect Snacks from Around the World, from the University of Kentucky, is an interesting article about insects that are eaten for food around the world.


Most Insects Exhibit Poor Parenting Skills, from Purdue University, is an interesting article about insects exhibiting poor parenting skills.


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Lesson Details

Grades Themes Type Project 2061 Benchmarks

Other Lessons in This Series

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