• CCB Science pages 102 - 109



  • Define symbiosis

  • Describe mutualism, commensalism, and parasitism

  • Give real-world examples of each type of symbiotic relation ship

Key Concept

  • The term symbiosis describes specific kinds of relationships between organisms in the same environment.


Tier 2 host
Tier 3 antibodies
Test Words summarize

Evidence-Based Reading

  • Word Parts: Write the word symbiosis on the board. Underline the base word bios. Explain that its history is Greek, and means one’s life, or way of living. Next, explain that letters attached to the beginning and end of a base word, or affixes, change the meaning of the word. Letters attached to the beginning are called prefixes. Circle the prefix ‘symand’ explain that it means together. Explain that letters attached to the end of a word form a suffix. Circle the suffix -is. Explain that it most closely means having the character of. Ask students to use their understanding of the word parts to define the term symbiosis.

21st Century Skill

  • Critical Thinking and Problem Solving: Invite volunteers to talk about the university website they researched. Have students identify their chosen universities and describe the kinds of science investigations that are being conducted there. Ask them to state the hypotheses university scientists are studying and the methods they’re using. Encourage students to talk about the investigations that most intrigue them.

Writing Practice

  • Remind students to think through the different kinds of symbiosis before writing. Students should describe the interaction of the mother and the puppy before identifying the kind of symbiotic relationship the two share. Mothers and offspring have a parasitic relationship, as developing fetuses and newborns depend on the mother for resources, leaving fewer resources for the mother.

Before Lesson

This lesson requires students to be familiar with biotic and abiotic factors in the environment. To determine their readiness, write the words living and nonliving on the board. Ask students to describe some of the living and nonliving things they see around them. Record their responses on the board. Then have students go beyond the classroom to consider spaces on the school campus. Continue adding students’ examples to the lists on the board.


Explain to students that in any ecosystem, living things interact with each other and with the physical environment. These organisms are constantly competing for resources, such as food, water, and shelter. Organisms live symbiotically, or with other living things. The relationships that organisms share may benefit both, harm one organism, or help one while having no effect on another. Ask students to think of examples of familiar symbiotic relationships within a family, such as a parent and child or two siblings. Invite students to talk about how the two members of those relationships interact and help or benefit one another.

Guided Practice

  • Interactions Among Living Things
    • Mutual Symbiosis
    • Termites and Bacteria
    • Acacia Trees and Ants
    • Ox-peckers, Rhinos, and Zebras
    • Humans and E. coli
  • Parasitic Symbiosis
    • The Tick
    • The Tapeworm
  • Commensal Symbiosis
    • The Pseudo-scorpion and Beetles
    • Cattle Egrets and Livestock
    • Sharks and Remoras

Core Skill

Identify Hypotheses: Read the sidebar text aloud. Give students time to consider the scientists’ observations of the acacia trees and form hypotheses. Invite students to share their ideas. Record their ideas on the board. (Acacia trees do not have a mutually beneficial relationship with the different kind of ant.)

Summarize Text: Remind students to think about what, why, and how as they reread their summaries. Tell them to be sure these three questions are addressed.


Summarize and Illustrate: Organize students into small groups. Have students reread different sections of the text aloud (“Mutual Symbiosis,” “Parasitic Symbiosis,” and “Commensal Symbiosis”) and explain what they have read in their own words. Have them select one section to label and illustrate.

Hypothesize and Propose an Experiment: Have students review the lesson and the organisms mentioned in it. Invite students to choose an organism, ask a question that can be answered through an investigation, form a hypothesis, and propose an experiment. You may want to ask students to write their hypotheses and proposals.

Lesson Review