Ecosystem Dynamics & Trophic Cascades

[!] STUDY GUIDE: Big Ideas Use to answer form questions

1.Ecosystems are dynamic; populations fluctuate and respond to changes. Students often think ecosystems are stable and unchanging, but evidence from investigations shows otherwise. Use data from today's stations to identify which observations best support this understanding.

2.Food webs are complex networks; removing one species affects many others. Students often think energy flows in simple linear food chains, but evidence from investigations shows otherwise. Use data from today's stations to identify which observations best support this understanding.

3.Biodiversity provides ecosystem services, resilience, and stability. Students often think biodiversity is 'nice to have' but not essential, but evidence from investigations shows otherwise. Use data from today's stations to identify which observations best support this understanding.

DRAW KEY TERMS Google each → Images tab → sketch what you see

The 10% Energy Rule

Only about 10% of energy transfers between trophic levels

Trophic level

Position in food chain (producer, primary/secondary consumer, apex predator)

Real Data from Yellowstone

Scientists have tracked population changes since wolf reintroduction in 1995

Trophic Cascade

When changes at one trophic level affect all other levels

OTHER VOCAB: keystone species · 10% rule · apex predator · biodiversity · ecosystem

WRITE FOCUS QUESTION Your initial thinking

After wolves were hunted out of Yellowstone in the 1920s, elk herds exploded and stripped riverbanks bare. When wolves were reintroduced in 1995, trees grew back, roots stabilized the soil, and rivers literally changed course.

Why did removing wolves from Yellowstone change the rivers?

I think...

WRITE AFTER HOOK FORM Reflect before continuing

I learned that...

Station 1 — Trophic Cascade Simulation

I observed that...

This shows that...

The key concept is...

WRITE STATION 2 NOTES Complete during Form 3 (Station 2)

Station 2 — Food Web Analysis

Main idea I observed:

Evidence from my data:

I can apply this by:

Station 2 — Food Web Analysis

The data shows...

This connects to...

Station 3 — Design a Conservation Plan

The main idea is...

This connects to what we learned because...

I can apply this by...

DRAW CONCEPT MODEL Show your understanding visually

Draw a Yellowstone food web showing the trophic cascade after wolves were removed (1920s) vs. after reintroduction (1995). Show 5 levels: wolves → elk → willows → beavers → river morphology. Use arrow thickness for energy flow (10% rule); circle the keystone species; label one apex predator.

Suggested labels: trophic level · trophic cascade · keystone species · 10% rule · apex predator · biodiversity · ecosystem

Labels included

Relationships shown

Key terms used

CHECK TEST YOUR THINKING Rate each: FALSE ← 1-2-3-4-5 → TRUE

1. Ecosystems are naturally stable and stay the same unless humans disturb them.

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2. Energy in a food web flows in a simple straight line from producer to top predator.

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3. Biodiversity is nice to have but not essential for an ecosystem to function.

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4. A keystone species matters only when its population is large enough to dominate other species in the ecosystem.

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5. [Last week · C7W4] Mass extinctions in Earth's past were random events that didn't reshape today's ecosystems.

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6. [Spiral · C4W3] More nutrients flowing into a stream or pond are always good — fertilizer runoff boosts ecosystem biodiversity.

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Pick any TWO statements -- especially any you rated 2, 3, or 4. Justify your rating with evidence:

Statement #___ -- I rated it ___ because:

THINK SCIENTIST CIRCLE DEBRIEF Reflect after your Scientist Circle discussion

AHA! Moment

The one I changed my thinking most about is...

Remaining Question

I still wonder...

WRITE FOCUS QUESTION REVISIT Final written response

Why did removing wolves from Yellowstone change the rivers?

Word Bank: trophic level · trophic cascade · keystone species · 10% rule · apex predator · biodiversity · ecosystem · The 10% Energy Rule