ecology

To begin, students view a video about the trophic cascade that resulted when wolves were reintroduced to Yellowstone. Next, students learn about food chains and food webs. They construct and analyze a food web for Yellowstone National Park. Finally, students use what they have learned to better understand the trophic cascade caused by the return of wolves to Yellowstone.

This learning activity provides an introduction to the learning activities, Carbon Cycles and Energy Flow through Ecosystems and the Biosphere and Trophic Pyramids. All three of these activities are included in Food Webs, Energy Flow, Carbon Cycle and Trophic Pyramids, which is intended for classroom instruction.

In this analysis and discussion activity, students learn why the biosphere requires a continuous inflow of energy, but does not need an inflow of carbon atoms. Students analyze how the process of photosynthesis illustrates the general principles of conservation of matter and the second Law of Thermodynamics.

Then, students analyze how carbon cycles and energy flow through ecosystems result from photosynthesis, biosynthesis, cellular respiration, and the trophic relationships in food webs. Thus, students learn how important ecological phenomena result from processes at the molecular, cellular and organismal levels.

To begin this analysis and discussion activity, students review what happens to the atoms in the nearly 2000 pounds of food the average American eats each year. This provides a context for students to figure out why the rate of biomass production is higher for the producers than for the primary consumers in an ecosystem.

Then, students construct and analyze trophic pyramids. Finally, they apply what they have learned to understanding why more resources are needed to produce meat than to produce an equivalent amount of plant food.

This overview summarizes major ecological concepts and recommends learning activities on topics such as food webs, energy flow through ecosystems, the carbon cycle, trophic pyramids, exponential and logistic population growth, species interactions in biological communities, succession, and effects of human activities on ecosystems. This overview also recommends introductory ecology readings. 

To begin this hands-on, minds-on activity, students view a video about ecosystem changes that resulted when wolves were reintroduced to Yellowstone. Then, students learn about food chains and food webs, and they construct and analyze a food web for Yellowstone National Park. Students use what they have learned to understand trophic cascades caused by the return of wolves to Yellowstone.

Next, students learn that the biosphere requires a continuous inflow of energy, but does not need an inflow of carbon atoms. To understand why, students analyze how the carbon cycle and energy flow through ecosystems result from photosynthesis, biosynthesis, cellular respiration, and the trophic relationships in food webs.

In the final section, students use the concepts they have learned to understand trophic pyramids and phenomena such as the relative population sizes for wolves vs. elk in Yellowstone. Thus, students learn how important ecological phenomena result from processes at the molecular, cellular, and organismal levels.

For virtual instruction, you can use Food Webs – Understanding What Happened When Wolves Returned to Yellowstone, Carbon Cycles and Energy Flow through Ecosystems and the Biosphere, and Trophic Pyramids. 

This analysis and discussion activity engages students in understanding how biological communities remain stable and how they change during ecological succession.

Students analyze several types of research evidence, including (1) repeated observations of a biological community to assess stability or change over time, (2) analyses of dated fossils in a peat bog, and (3) analyses of how mutualism, competition and trophic relationships contribute to stability or change in biological communities.

Students use this evidence to understand the causes of stability and succession in a variety of habitats, including a tropical forest, a new volcanic island, abandoned farm fields, and ponds. Students also analyze the effects of climate and non-native invasive plants.

The Student Handout is available in the first two attached files and as a Google doc designed for use in online instruction. The Teacher Notes, available in the third and fourth attached files, provide background information and instructional suggestion and explain how this activity is aligned with the Next Generation Science Standards. A PowerPoint with illustrations of each habitat is available in the last attachment.

This analysis and discussion activity engages students in understanding the lifecycle and adaptations of black-legged ticks and the relationships between these ticks, their vertebrate hosts, and the bacteria that cause Lyme disease.

Students use this background to analyze when and where human risk of Lyme disease is greatest, why rates of Lyme disease have increased in recent decades in the US, and ecological approaches to preventing Lyme disease.

In this analysis and discussion activity, students develop their understanding of the exponential and logistic population growth models by analyzing the recovery of endangered species and growth of bacterial populations. Students learn about the processes that cause exponential or logistic population growth, interpret data from several investigations, and apply their understanding to policy questions.

Next, students analyze examples where the trends in population size do not match the predictions of the exponential or logistic population growth models. They learn that models are based on simplifying assumptions and a model’s predictions are only accurate when the simplifying assumptions are true for the population studied.
In the last section, students analyze trends in human population size and some of the factors that affect the earth’s carrying capacity for humans. 

One version of the Student Handout also includes mathematical equations for exponential and logistic population growth. Appendices to these Teacher Notes offer optional questions on food poisoning, exponential growth of a rabbit population, additional examples of exceptions to the logistic population growth model, and a research challenge (to develop proposals for sustainable use of two resources that may limit the earth’s carrying capacity for humans).

The resources include:

First, students analyze a hypothetical example of exponential growth in the number of infected individuals.

Then, a class simulation of the spread of an infectious disease shows a trend that approximates logistic growth.

Next, students analyze examples of exponential and logistic population growth and learn about the biological processes that result in exponential or logistic population growth.

Finally, students analyze how changes in the biotic or abiotic environment can affect population size; these examples illustrate the limitations of the exponential and logistic population growth models.