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Ecosystems | Lesson 2 - Patterns in Biomass in Ecosystems

Overview

Students use a simulation of a meadow ecosystem to view changes in the organic mass of populations of producers, herbivores, and carnivores from different initial population. They then compare their findings with different real ecosystems to highlight an important common pattern: the organic matter pyramid. In most terrestrial ecosystems, there is more organic matter in producers than in herbivores and more organic matter in herbivores than in carnivores. They will use carbon-transforming processes to explain this pattern in Lesson 3.

Guiding Question

What are the patterns in organic matter pools in ecosystems?

Activities in this Lesson

  • Activity 2.1: Predictions and Planning for the Meadow Simulation (30 min)
  • Activity 2.2: The Meadow Simulation (50 min)
  • Activity 2.3: Evidence-Based Arguments for the Meadow Simulation (40 min)
  • Activity 2.4: Organic Carbon Pools in Other Ecosystems (20 min)

Unit Map

Ecosystems Unit Map

Target Student Performance

Activity

Target Performance

Lesson 2 – Patterns in Organic Matter in Ecosystems (students as investigators)

Activity 2.1: Predictions and Planning for the Meadow Simulation

Students make predictions about changes in the mass of different populations in a meadow ecosystem and plans to maximize the fox population.

Activity 2.2: The Meadow Simulation

Students identify patterns in relationships among organic mass of populations at different trophic levels in a simulated meadow ecosystem (the organic matter pyramid).

Activity 2.3: Evidence-Based Arguments for the Meadow Simulation

Students develop arguments from evidence about possible patterns in relationships among mass of populations at different trophic levels in a simulated meadow ecosystem (the organic matter pyramid).

Activity 2.4: Organic Carbon Pools in Other Ecosystems

Students describe patterns in relationships among mass of populations at different trophic levels in a other ecosystems (the organic matter pyramid).

NGSS Performance Expectations

High School

  • Interdependent Relationships in Ecosystems. HS-LS2-1. Use mathematical and or computational representations to support explanations of factors that affect carrying capacity of ecosystems and different scales.

Middle School

  • Interdependent Relationships in Ecosystems. MS-LS2-2. Construct an explanation that predicts patterns of interactions among organisms across multiple ecosystems.
  • Matter and Energy in Organisms and Ecosystems. MS-LS2-4. Construct an argument supported by empirical evidence that changes to physical or biological components of an ecosystem affect populations.
  • Matter and Energy in Organisms and Ecosystems. MS-LS2-1. Analyze and interpret data to provide evidence for the effects of resource availability on organisms and populations of organisms in an ecosystem.
Three-dimensional Learning Progression

This Lesson includes three activities in which students begin to analyze ecosystems as systems that are constantly transforming matter and energy rather than as collections of plants and animals in a particular setting.

Key Ideas and Practices for Each Activity

In Activity 2.1 students make the transition from a picture of a meadow as a place where plants and animals live to a more abstract representation of the organic mass of populations of producers, herbivores, and carnivores in an ecosystem and make predictions about mass of each group in a meadow.

In Activity 2.2 students use an online simulation to investigate the relative sizes of the organic mass of populations of producers, herbivores, and carnivores and how they change over time. The Meadow Simulation allows students to run multiple scenarios adjusting initial populations of grasses, rabbits, and foxes to observe changes in the mass of the populations over a 100-year period.

Through the online simulations students will need to notice two patterns: 1) the mass of the populations of producers, herbivores, and carnivores changes over time and 2) over time a consistent pattern emerges: The mass in the rabbit population is smaller than the grass biomass, and mass in the fox population is always the smallest. Different initial mass of grasses, rabbits and foxes lead to different patterns of change, but the foxes can survive only if the grass mass stays large.

In Activity 2.3 students complete the Evidence-Based Arguments Tool for the patterns of change in carbon pools that they observed in the Meadow Simulation. In addition to describing the pattern that they have observed—the organic matter pyramid—they formulate questions about why that pattern emerges for many different original settings. They will answer these questions in Lesson 3.

In Activity 2.4, students are introduced to the amount of organic carbon in different ecosystems. They observe the same pattern in producers, herbivores, and carnivores in four different types of ecosystems that have different amounts of total organic matter. They also see that in most terrestrial ecosystems, the largest organic matter pool is soil carbon. (Ecologists would say that the organic matter pyramid should more accurately be applied to production—the rate of biosynthesis at each trophic level—rather than biomass. There are aquatic ecosystems where the producers—phytoplankton—grow very fast and are eaten very fast, so there is more mass stored in consumers. This is not an important point for this Unit.)

Content Boundaries and Extensions