Lesson 6 — Species in Relationship

Summary

Learners map the three great relationships among species — predation, competition, and symbiosis — and see how they weave communities together into food webs. They build a web (with string and bodies), classify real pairs, and trace a ripple when one species changes.

Objectives

• Describe relationships among species (predation, competition, symbiosis) and how they shape communities. (D06.S2.07.02)

Connection

In a coral reef, a clownfish hides among the stinging arms of a sea anemone; the fish is protected and the anemone is cleaned and fed — both benefit. A few metres away, two kinds of fish chase the same shrimp: that is competition. And a reef shark eats a smaller fish: that is predation. A forest, a savanna, a rice paddy, a city park — every community of living things is stitched together by these three kinds of relationships, and a change to one ripples through the rest.

Materials

• Relationship card set
• Community web page
• String and clips

Preparation

• Copy the relationship card set and the community web page; gather string and clips.
• Have the worked example ready: grass → rabbit → fox (predation); rabbit and deer on the same grass (competition); bee and flower (symbiosis/mutualism).
• Retrieval: recall from Grade 5–6 (D06.S2.05.01, D06.S2.06.02) how energy moves through a food web.

Facilitator note

This lesson is written to the learner (“you”). The ideas to land: (1) predation — one species eats another; (2) competition — two species use the same limited resource; (3) symbiosis — two species live closely together, and in mutualism both benefit; and (4) these relationships, together, structure a community. Use explicit instruction with the grass–rabbit–fox worked example first, then the string-web for embodied practice (Kirschner, Sweller & Clark, 2006). These are standard concepts in ecology; classic examples are real: lichens (a fungus and algae living together), clownfish and sea anemones, oxpeckers and large mammals, nitrogen-fixing bacteria in legume roots. The environment lens (docs/philosophy.md §4): removing one species can cascade — wolves were wiped out of Yellowstone by the 1920s, and their return in 1995–1996 reduced elk numbers and browsing, helping some willows and aspen recover (a real, well-studied — though complex and still-contested — trophic cascade; the simplified “wolves changed the rivers” story overstates it). The egalitarian and global lens: cooperation is as real in nature as competition; symbiosis shows that “nature red in tooth and claw” is only half the story — living things also depend on each other. This counters the misuse of “competition” as a social rule.

Procedure

1. Gather (5 min). Quick recall: what three ingredients make populations change over time? (Variation, inheritance, selection.) Today we zoom out: how do species relate to each other?
2. Meet the three relationships (10 min). Predation: one species eats another (fox → rabbit → grass). Competition: two species use the same limited resource (rabbit and deer both eat grass). Symbiosis: two species live closely together; in mutualism, both benefit (bee gets nectar, flower gets pollinated).
3. Worked example (5 min). Classify aloud: a lion and a gazelle (predation); two birds eating the same berries (competition); a clownfish and an anemone (symbiosis, mutualism).
4. Build the web (20 min). With string, each learner becomes a species in a small community. Pass string from food to eater (predation), tie two species to the same food (competition), and join two helpers (symbiosis). Now pull one string: what ripples?
5. Classify (5 min). Sort your relationship cards into the three types with a partner, and name one real example of each from your own place.
6. Close (5 min). Predation, competition, and symbiosis are the threads that weave a community together — and a change to one thread pulls on the rest.

Differentiation

• Support: Use only “who eats whom” (predation) first, then add one competition and one symbiosis example; describe the web aloud so learners with low vision can follow.
• Extension: Trace a trophic cascade (e.g., wolves in Yellowstone): explain how removing wolves let elk over-browse willows and aspen, and how their return reduced elk and helped some of those plants recover.

Assessment

• Formative (observation/self): Can the learner classify a species pair into predation, competition, or symbiosis and describe one ripple effect of a change?
• Self-check: The learner asks, “Did I name the relationship precisely (who eats whom, who shares a resource, who helps whom) and connect it to the wider community?”

Home connection

Find one real species relationship near you — a bird eating an insect, two animals eating the same fruit, a bee on a flower. Name which of the three it is and share it next time.

Resources

• Predation, competition, and symbiosis are standard concepts in ecology; documented examples include lichens (fungus + algae), clownfish and sea anemones, oxpeckers and large mammals, and nitrogen-fixing bacteria in legume roots. The wolf–Yellowstone case is a real, well-studied trophic cascade: wolves were extirpated by the 1920s and reintroduced in 1995–1996; their return reduced elk numbers and browsing, and willow/aspen recovery followed in places — though the ecosystem’s response has been complex and the simplified “wolves changed the rivers” story is contested in the ecological literature. The value that cooperation is as real in nature as competition is a value commitment, not an ecological claim (docs/philosophy.md §4–5).
• On explicit instruction for novice content: Kirschner, Sweller & Clark (2006), https://doi.org/10.1207/s15326985ep4102_1