Week 2: Ecosystem Disruption & Invasive Species

Grade 8 Science | Rosche | Kairos Academies

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Need Support?: Look for green and red "Hint" and "Walkthrough" boxes!
Common Mistake โ€” Read Before Solving

WRONG: "WRONG: "WRONG: "WRONG: "Cane toads are invasive because they're ugly and poisonous.""""

RIGHT: "RIGHT: "RIGHT: "RIGHT: "Cane toads are invasive because they're non-native and outcompete natives. Predators haven't evolved defenses against their poison.""""

Step-by-Step Solution

Step 1: Identify what you know & what changed

"BEFORE: 10,000 birds eating 800 kg insects/year
AFTER: <500 birds eating 40 kg insects/year
NEW TOP PREDATOR: 5,000 snakes ร— 2 birds/snake = 10,000 birds eaten per year"

Step 2: Identify the trophic levels affected

"Level 4 (new): Snakes (invasive apex predator)
Level 3: Birds (native predators) โ€” DECLINING
Level 2: Insects (prey) โ€” INCREASING (less predation)
Level 1: Plants โ€” DECLINING (more herbivore damage from insects)"

Step 3: Calculate the change in insect predation

"Change in insect predation = 800 kg - 40 kg = 760 kg fewer insects eaten
Percent change = (760 / 800) ร— 100% = 95% REDUCTION in insect predation
This means insect populations likely EXPLODED because their predators (birds) were removed by snakes"

Now YOU Complete Steps 4-5:

Step 4: Explain why this is a "top-down" cascade (use the trophic levels from Step 2)

Step 5: Predict what happens to plant populations on Guam. Use the 10% rule from Week 1 to explain why removing one predator (snakes) wouldn't immediately fix the problem.

Fading Support: Week 1 showed all 5 steps. This week, steps 4-5 are YOUR turn. By Week 3, you'll do most steps independently! This builds your problem-solving stamina.

๐Ÿ†˜ Stuck? Click for step-by-step help
Detailed walkthrough when you need more guidance.

Try these steps in order:

  1. Draw the food web with arrows showing "who eats whom"
  2. Circle the species being added or removed
  3. Ask: "If this species increases, what happens to what it EATS?"
  4. Ask: "If this species increases, what happens to what EATS IT?"
  5. Follow the chain up and down until you reach producers
  6. Review the Yellowstone wolves example in Station 1 content above
COMPLETE THE STATION 1 FORM โ€” Click to Open

Model cascade effects and predict outcomes.

Complete Your Worksheet โ€” Click to Expand

Complete the "Station 1" box in the "STATION 1 & 2 NOTES" section:

  • When predators are removed... (what happened to elk?)
  • The effect ripples because... (trace the cascade)
  • Key insight: (one sentence summary)

Simulation: Trophic Cascade

PREDICT (before running the sim)

Look at the simulation controls. Before changing any variables, predict what will happen when you adjust them. Write your prediction down.

OBSERVE (while using the sim)

Change one variable at a time. Record what happens after each change. Use the data journal to capture at least 3 trials.

EXPLAIN (after collecting data)

Compare your observations with your prediction. Use scientific vocabulary to explain the patterns you found. What surprised you? What confirmed your thinking?

Station 2 โ€“ Case Study Analysis

20 Points | ~15 Minutes

Compare real invasive species case studies to identify patterns of ecosystem disruption.

CER SCAFFOLD โ€” Build your response in this order:
โ–ถ CLAIM

Your Mission: Analyze Real Invasive Species Data

Case Study Comparison Table

Species Location Why Invasive? Impact
Cane Toad Australia Poisonous, no predators Native predators die eating them
Zebra Mussel Great Lakes Filter-feeders, reproduce fast 150,000/mยฒ, clog pipes, starve natives
Kudzu Southern US Grows 1 ft/day, no herbivores Smothers native trees
Brown Tree Snake Guam Island birds had no defenses 10/12 bird species EXTINCT

Look for Patterns!

All successful invasive species share these traits:

  • No natural predators in their new environment
  • Fast reproduction (high birth rate)
  • Generalist diet (can eat many things)
  • Native species haven't evolved defenses (Cycle 3 connection!)
Need extra support? Click for analysis hints
Strategies for comparing case studies and identifying patterns.

Analysis Strategy:

  • Compare: What do all 4 invasive species have in common?
  • Contrast: How are the impacts different?
  • Connect: How does the 10% rule explain why there are so many toads/mussels?

Sentence Starters:

  • "All four species succeeded because..."
  • "The 10% rule explains the impact because..."
  • "Native species couldn't adapt because..."
COMPLETE THE STATION 2 FORM โ€” Click to Open

Analyze case studies and identify patterns.

Complete Your Worksheet โ€” Click to Expand

Complete the "Station 2" box in the "STATION 1 & 2 NOTES" section:

  • The invasive species disrupted... (what did it affect?)
  • Native species were harmed by... (mechanism)
  • Key insight: (one sentence summary)
COMPLETE THE STATION 2 FORM

Complete the form below for Station 2.

Complete Your Worksheet โ€” Click to Expand

Complete the "STATION 3 NOTES" section on your worksheet:

  • One intervention strategy is... (what approach did you design?)
  • This works (or fails) because... (mechanism)
  • A tradeoff or unintended consequence... (what could go wrong?)
  • Key insight: (one sentence summary)
COMPLETE THE STATION 2 FORM

Complete the form below for Station 2.

Complete Your Worksheet โ€” Click to Expand

Complete the "DAY 2 EXIT TICKET" and "SCIENCE CIRCLE" sections:

  • Q1 (NEW): How invasive species disrupt energy flow
  • Q2 (SPIRAL): Apply the 10% rule to predator removal
  • Q3 (INTEGRATION): Connect cascades to energy pyramids
  • Science Circle: Your "Aha!" moment and remaining question

Bonus: +5 points for Day 2 Exit Ticket, +3 points for Science Circle!

COMPLETE THE STATION 2 FORM

Complete the form below for Station 2.

Enrichment & Extension
Optional deep dives into invasion biology, scientist profiles, and environmental justice.

Optional content if you finish early or want to go deeper.

Scientist Spotlight: Dr. Daniel Simberloff

Dr. Daniel Simberloff is a pioneering ecologist who revolutionized the study of invasive species and ecosystem disruption. His research on island biogeography showed why island species are particularly vulnerable to invasive predatorsโ€”they lack evolved defenses because they evolved in isolation. His work helped establish the field of invasion biology, demonstrating how non-native species cause trophic cascades that destabilize entire food webs. Dr. Simberloff's studies have informed conservation policies worldwide, protecting vulnerable ecosystems from biological invasions.

Environmental Justice: Who bears the burden?

Invasive species disproportionately harm low-income communities who depend on fishing, foraging, and subsistence hunting. Along the Mississippi River near St. Louis, Asian carp and zebra mussel invasions devastated small-scale commercial fishers and recreational fishing tourism in riverside communities. While wealthy suburbs invest in invasive species management, working-class river communities lack resources to protect their livelihoods. Environmental justice requires asking: Who loses when ecosystems are disrupted, and who has power to prevent invasions?

Week 2 Complete!

Next Week: Synthesis & Assessment โ€“ Bringing it all together!