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18.2: Lesson 18.1: Ecosystems

Difficulty Level: At Grade Created by: CK-12

Key Concepts

  • Definition of ecosystem
  • Abiotic factors
  • Biotic factors
  • Roles in ecosystems
  • Flow of energy through ecosystems
  • Flow of matter through ecosystems

Lesson Objectives

  • Define ecosystem, and give examples.
  • Identify abiotic factors in ecosystems.
  • Describe biotic factors in ecosystems.
  • Explain how energy flows through ecosystems.
  • Outline how matter moves through ecosystems.

Lesson Vocabulary

  • abiotic factor: nonliving part of an ecosystem such as air or soil
  • biotic factor: living part of an ecosystem such as a species of producers
  • carnivore: consumer that eats only animals
  • community: all the populations of all the species that live together in an ecosystem
  • consumer: organism that consumes other living things
  • decomposer: organism that breaks down dead organisms or the wastes of living things and releases their nutrients back into the environment
  • ecosystem: group of living things and their environment
  • food chain: simple diagram showing one way that energy flows through an ecosystem
  • food web: complex diagram showing multiple ways that energy flows through an ecosystem
  • grazer: organism that feeds on other living things without killing them
  • habitat: place where a species is best suited to live
  • herbivore: consumer that eats only plants
  • niche: a species’ particular way of “making a living”
  • nutrient: nonliving matter that living things need
  • omnivore: consumer that eats both plants and animals
  • population: all the members of a species that live in the same area
  • predator: consumer that hunts and captures other living things for food
  • prey: organism that is hunted by a predator
  • producer: organism that uses energy to make food for itself and other living things
  • scavenger: consumer that eats organisms that are already dead
  • species: unique group of organisms that can interbreed and produce fertile offspring together but not with members of other such groups

Teaching Strategies

Introducing the Lesson

Most students will have been introduced to ecosystems in prior classes, such as life science. Help them recall what they already know. Call on volunteers to define the term ecosystem. Call on other students to give examples of ecosystems or to state facts they know about ecosystems. Accept all reasonable responses at this point. Then tell students they will learn more about ecosystems when they read this lesson.

Building Science Skills

Students can practice identifying the roles played by different species in an ecosystem by playing the game at the URL below. They have the option to play the game with four different ecosystems.



Have students complete the food web worksheet at the following URL. They will identify the roles played by different organisms in a food web and then create a food web of their own.


Differentiated Instruction

This lesson introduces many new vocabulary terms, and some of them are extremely important and basic terms. Assign several of the most important vocabulary terms from the lesson to pairs of students, and ask partners to add their term to the world wall. For each word, students should write the term on an index card, define it, and give examples. Important terms to assign include all or some of the following: ecosystem, community, niche, population, and/or species.


Ask a few students to make crossword puzzles that include at least 12 of the lesson vocabulary terms. Suggest that they avoid straightforward definitions of the terms as clues in order to make their puzzles more challenging. Make copies of the puzzles to distribute to the rest of the class, and have the other students complete the puzzles as a homework assignment.

Science Inquiry

In the inquiry activity “Ecosystems at School” (see URL below), students will demarcate an outdoor ecosystem, study it, and identify its biotic and abiotic components. The activity could be done on the school grounds or in a park or other natural area.


Common Misconceptions

Students commonly think that organisms higher in a food chain eat everything that is lower in the food chain. Be sure to correct this misconception in your students. Explain that organisms higher in a food chain eat some, but rarely all, of the organisms below them in the food chain. Give them concrete examples that demonstrate this point. For example, call students’ attention to the sample food chain in the FlexBook® lesson, and discuss how the hawk (tertiary consumer) may eat the other bird (secondary consumer) but is unlikely to eat the snail (primary consumer) because it is so small, and it would never eat the grasses or other plants (producers) because the hawk is a carnivore.

Reinforce and Review

Lesson Worksheets

Copy and distribute the lesson worksheets in the CK-12 Earth Science for Middle School Workbook. Ask students to complete the worksheets alone or in pairs to reinforce lesson content.

Lesson Review Questions

Have students answer the Review Questions listed at the end of the lesson in the FlexBook® student edition.

Lesson Quiz

Check students’ mastery of the lesson with Lesson 18.1 Quiz in CK-12 Earth Science for Middle School Quizzes and Tests.

Points to Consider

In this lesson, you read that matter is recycled in ecosystems. You already know how water is recycled. Its cycle includes living things, the air, and the oceans. In the next lesson, you’ll read about the cycles of two important nutrients, starting with carbon. Can you predict how carbon cycles?

Do you think carbon cycles between living and nonliving things?

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