Core Unit: Ecosystems

Energy transformations and food webs in the ecosystems should be examined. How do the abiotic factors within the ecosystem enable life to be sustained? If the ecosystem changes with time, students might consider how the change has affected life within the ecosystem.

The students might need to establish criteria for what constitutes a grass "plant." They might consider that each stem emerging from the ground represents a single plant, even though grass sends out underground stems through vegetative reproduction.

Calculate the total area of the lawn. Estimate the total number of grass plants in the lawn. Have the students establish a method for determining this. (Divide the total area of the lawn by the area used in making each count. Multiply the result by the number of plants in the counted area. Make any necessary adjustments to the calculations to account for such things as bare spots on the lawn, competing vegetation growing on the lawn, or sparse growth in some places on the lawn.)

Discuss the idea that some estimates have more credibility than others. Estimates should always be more than just "wild guesses." They must be reasonable. Are the results reasonable? Consider any assumptions that have been made in arriving at the estimate.

Consider the variety of plant species within a given area. Does a larger variety indicate a healthier ecosystem? Consider why bare spots exist. Are they indicative of a healthy ecosystem?

This procedure can be used to estimate populations such as trees in a forest, wildflowers or weeds in a field, plants in a field crop, and so on.

Crop specialists or extension agrologists could be interviewed on methods of crop rotation.

For successful group work, all students must contribute to the group effort. Encourage students to share and rotate the responsibilities for the required tasks, such as investigating, observing, recording, and reporting.

Magnifying glasses, small garden tools for digging, scissors, tweezers, assorted jars and containers with lids, shoe boxes, and plastic bags are some things that students might use in this activity. While the investigation is taking place, students can collect samples for further investigation in the classroom.

Students should record the kind and number of each organism they find in their plot. Any indirect evidence of life, such as animal droppings or burrows, should also be noted. Students should try to determine if organic matter on the ground came from plants within the plot or was transported in from elsewhere. Dig up some of the soil in the plot and examine it for any further evidence of animal life. Emphasize the need for the careful recording of what has been observed.

Relationships and interactions among biotic and abiotic factors in their study plot should be examined carefully. Abiotic factors which help to support life should be noted.

Teachers may wish to assist students in developing organizers for their observations, to provide more structure to this learning experience. If so, here are some categories that students might consider.

• date and time of visit
• seasonal considerations
• weather and climatic conditions
• vegetation
• small animals found beneath the ground
• large animals found beneath the ground
• small animals found on the ground
• large animals found on the ground
• animals found on vegetation
• flying animals likely to visit the area
• moving animals likely to visit the area

Other ways of organizing the observations are encouraged. Before the actual study is conducted, students could plan learning activities in collaboration with their peers and with the teacher.

Using estimating techniques similar to those in the previous activity, students can measure the area of a much larger section of the field and estimate the number of a particular kind of living organism that might be found there.

Caution students about things like broken glass, insect bites, bee stings, and poison plants that they might experience in the area they survey.

Interrelationships between living and nonliving things in the environment are very complex. We are only just beginning to appreciate some of those complexities. One thing, however, is virtually certain. If people do not act quickly to protect the environment, the destruction that would otherwise occur could have a devastating impact. All life forms on Earth could be threatened, including the human race. By developing an awareness of nature's beauty, students may begin to value its preservation.

Students must develop an awareness that all forms of life need to be protected.

Humans have the responsibility for preserving the environment. Endangered species can, in many cases, be saved if people act quickly and responsibly. All things are interrelated. A change in one ecosystem, however small that change might be perceived to be, may have serious global consequences.

Remove one of the animals once the food chain has been constructed. Consider how other animals in the ecosystem would be affected.

Imagine that the population of one of the animals in the ecosystem suddenly increased dramatically. Identify what changes might occur as a result.

Simulate human encroachment in the ecosystem. Imagine that some of the habitats are destroyed, or various types of pollutants are introduced. Consider the implications that these types of changes would have on living things within the ecosystem. Research actual case studies involving these changes.

The intricacy of the connections, graphically illustrated with the string, gives students a better understanding of the complexity of biotic interrelationships within an ecosystem. By introducing a change into the ecosystem, students can begin to recognize what types of responses would occur.

See if you can establish the criteria that were used in selecting the site. Was it in close proximity to a populated area? Were there abiotic factors which influenced the selection of the site? Was the decision to use the site based primarily on economic or political factors? These are interesting things to research prior to the trip. Try to obtain newspaper articles describing a recent decision regarding the placement of a landfill site.

Examine the natural ecosystem within a short walking distance from the landfill site. Record some of the living things that thrive in that location.

At the landfill site, see what living things exist. How have the conditions changed to make it a preferable site for some life forms, but a less desirable site for others? What other changes might take place over time at this site? Perhaps the class could visit a very old landfill site which is now being used for some other purpose.

Classify the type of waste found at the site. What resources went into the production of the materials? How much energy was consumed in making, using, and disposing of the materials? How are materials sorted on the site? Which materials could be reused, recycled, reduced, or recovered? Which of the materials are biodegradable and non-biodegradable? Which materials might potentially leach into ground water? Which materials are potentially toxic? (Keep this in mind in planning the trip. Some materials may need to be identified beforehand as being hazardous, in order to not expose students to any potential harm. Establish clear guidelines with the class.)

What are some of the less obvious consequences of landfill? Are there any long-term global consequences that students might be able to identify? What are the alternatives? Are they any better or worse? Research "accidents" that have occurred at landfill sites, such as tire fires or explosions.

Landfill sites are not places that one would normally plan to visit -- unless, of course, one were interested in photographing seagulls! They are intentionally located so as not to become too objectionable or the subject of political controversy. It is worthwhile to visit a site like this occasionally, if only to serve as a reminder of the impact that humans have on the environment.

Farms are special environments within ecosystems. Farming results in a change in the way in which living things interact within the ecosystem. Examine life forms on the farm from this perspective. Determine how living things have either had to adapt or had to move as a result of the cultivation of land. Consider interviewing an older farmer to reflect on the changes that have taken place in agriculture over the years.

Investigate ways in which farmers are trying to protect natural ecosystems. Determine how interdependence develops in cultivated and natural areas. In what ways is the protection of natural ecosystems an advantage?

By examining changes that have taken place over a longer period of time Ä one or two generations at least Ä students will begin to appreciate that long-term changes in an ecosystem may cause it to take on very different characteristics.

Customary courtesies should be extended to Métis and Indian Elders. Offer transportation if they accept an invitation to visit the classroom. Arrange to provide gifts in exchange for information or service. Emphasis should be placed on sharing. During oral communication, students should ask a question and allow pause time for the question to be reflected upon before an answer is given. Permission to record an interview should be obtained beforehand. Other courtesies that are normally offered to any visitor to the school should be extended.

Students can use this experience to further their understanding of ecosystems. It serves as a good model of how larger, more complex ecosystems function.

Ask each student group to identify some aspect of the current prairie community and describe what it is like now and what it may be like 50 years from now. Ask them to consider both environmental and economic factors in their deliberations.