Title: Earth Out of Balance

Overview & Outcomes:

In Investigations Lesson 13 certain human activities that contribute to global warming through carbon dioxide production was examined as an example of the impact of human activity upon the environment. This lesson provides students with a dramatic demonstration of the impact of human activity on both terrestrial and oceanic ecosystems. Investigations Lesson 15 is the terminal Investigation section lessons in which students state and defend a position on the STS question presented in Foundations/Awareness Lesson 11: Is global atmospheric change (including enhanced greenhouse effect, ozone layer depletion and ground level ozone pollution) a threat?

This lesson helps learners:

• Represent various members of an ecosystem and visually create the food web which would exist within that system.

• Observe the effects of species loss upon biodiversity.

The concept map shows model relationships among concepts this lesson seeks to develop. Concepts introduced in this lesson are bolded on that concept map and concepts from other lessons are in plain text (not bolded).

Background Notes for the Teacher:

Content. Biodiversity refers to the variety and variability among many different living organisms and ecosystems that make up the earth's environment. These organisms interact with each other within that environment. Within this ecosystem all energy originates with the sun. The sun gives energy to producers (plants) who give energy to primary consumers (plant eaters) who provide energy to secondary consumers (primary consumer eaters). The loss of a certain species within this system can result in a shift in relationships among members of the community. Such shifts can eventually result in a system out of balance. The threats to global biodiversity arise from human activities. Habitats are destroyed or altered as forests are cut down for fuel, shelter, or agriculture. Rapid industrialization and rising standards of living have polluted habitats. Humans have hunted some animals to extinction. As habitats change, the availability of food, shelter, and water will change. While some species can migrate with the change or change behaviors, many will not be able to find new niches or adapt. Although extinction is a result of both non-human and human activities, human activities have greatly accelerated the rate of extinction. The rate of extinction (now faster than at any time in earth's history) currently results in the loss of an estimated 30 species a day.

Additional Teacher References.

1. Videos: NOTE: The teacher may elect to integrate on or more of these videos into the lesson.
   • Diversity Of Life, National Geographic Society

   • Ecology, Educational Activities Productions

   • Ecosystems, Hawk Hill Productions

   • Food Chains In The Biosphere, Hawk Hill Productions

   • The Ecosphere: Where All Life Exists, Chariot Productions

2. Ennis, C. A., Marcus, N. H. (1994). Biological Consequences of Global Climate Change. Colorado: Global Change Instruction Program of the Advanced Study program of the National Center for Atmospheric Research.

Materials:

For the class.

1. 1 large ball of yarn (yellow if possible)

2. Index cards for the following categories of organisms
   • Sun
   • Producers (plants)
   • Primary Consumers (plant eaters)
   • Secondary Consumers (primary consumer eaters)
   • Decomposers (bacteria, fungi)

   • Components for the terrestrial ecosystem should be printed on one side of the card in green marker, with the oceanic ecosystem components printed on the other side in blue marker.

   • Keep the numbers of organisms in each group proportionate to actual distributions. In other words, there should be far more producers than primary consumers, and far more primary consumers than secondary consumers, etc. Also, take class size into consideration.

   • You may wish to put a picture of the organism on each card (old magazines are a good source for these), or have the students find the pictures or draw their own pictures.

3. 1 large plastic inflatable globe

For each student.

1. 1 straight pin or tape

Preparation:

Collect materials and prepare index cards.

Instructional Procedures: (2 Days, 40 minutes each)

Day 1. (40 minutes)

1. Conduct a brief discussion of the terms biodiversity, producers, primary consumers, secondary consumers, and decomposers.

2. Distribute an index card and straight pin or a piece of tape to each student. Instruct them to attach the card to their clothing with the green print showing. (At this point you may wish to move your students outside to carry out the activity.)

3. Have students position themselves in a circle. Identify the ball of yarn as the sun and the yarn its energy. Since all the energy comes from the sun, the Sun begins the activity by wrapping the yarn around his/her finger, then giving its energy to a Producer by tossing the ball of yarn to a plant. (Each person receiving the yarn must first wrap the yarn around a finger before passing it on).

4. Instruct the Producer to identify a Primary Consumer in the circle who depends upon the Producer for food and toss the yarn to that student.

5. Instruct the Primary Consumer to identify either a Secondary Consumer or a Decomposer who depends upon the Primary Consumer for food and toss the yarn to that student. Remind the students that the sun's energy is being passed on as one organism consumes another.

6. From this point on students can identify any component in the circle that either they depend upon or depends upon them for food/energy. Require students to verbalize the component they have chosen and explain what relationship they have with that other component. Because students will receive the yarn more than once, the intricate relationships between organisms will be illustrated, thus creating a yarn web.

7. Continue the activity until the yarn is completely used, then place the inflatable globe in the middle of the web to demonstrate how biodiversity keeps the earth's ecosystems in balance.

8. At this point impose a human activity upon the ecosystem which could lead to the destruction of species. For example, "last night a spray was used to destroy all the insects in our ecosystem."

9. Instruct all insects to drop their yarn. In turn, instruct all organisms who depend upon insects for food or pollination to drop their yarn, and so on. Because the biodiversity of the ecosystem has been dramatically disturbed, the earth is now out of balance, and the globe will fall to the ground.

10. Question students as to why the earth is out of balance. Try to elicit that in an ecosystem, there is never just one species affected by human activity, and that as more species are eliminated, the system collapses.

11. Instruct students to turn their index cards to the other side, and repeat the activity as it relates to an oceanic ecosystem.

12. As a class, brainstorm a list of human activities that cause the loss of biodiversity within or across the terrestrial and oceanic ecosystem.

Day 2. (40 minutes)

1. Take the class outside to a green area-lawn, field, semi-wooded area. Instruct each student to select a patch of ground (the size and location of that patch should be agreed upon by you and your students) that they will be observing over a period of time (the length of which you also need to agree upon).

2. Explain to the students that they will be keeping a dated, observational log that should include the following:
   • Time of observation
   • Names, descriptions, and drawings of various plants, animals, and objects in the area
   • What appears and/or disappears
   • Weather conditions

3. Inform students that they will be writing a summary paper upon the project's completion enumerating the changes that took place and offering cause/effect explanations as to why they occurred.

Assessment/Portfolio Items:

Project. Observational patch log.

Other: Summary paper.

Click Here to go to Investigations Lesson 15: Where Do You Stand?