Ecosystem Builder
Build a sustainable food chain across complex terrain — or let the Solver do it for you in under 10 minutes. Two products, one goal: ace the Ecosystem scenario.
What is the Ecosystem Builder?
The Ecosystem Builder is a simulation scenario in McKinsey’s Solve assessment. You act as an environmental researcher tasked with constructing a sustainable food chain across a specific terrain. Your goal is to select a set of species that can survive together — each predator must have enough prey to meet its calorie requirements, every predator-prey pair must produce a calorie surplus, and all species must be compatible with the terrain and climate conditions of the site.
The difficulty comes from cascading constraints: a predator consumes whichever prey provides the greatest number of calories first, so the order and composition of your food chain affects the entire system. A single miscalculation collapses the ecosystem. Candidates need to hold multiple rules in mind simultaneously, under time pressure, without making an arithmetic error.
The rules
When multiple prey species offer the same calorie value, the predator consumes them equally. The ecosystem is only valid when every pair in the chain has a calorie surplus and every species is terrain-compatible. Verifying this manually is slow and error-prone — which is exactly why the Solver exists.
Why candidates struggle
Two ways to prepare.
Whether you want to understand the scenario deeply through practice or guarantee your score with the Solver, we have you covered.
Solve it in under 10 minutes.
Enter your food chain and the Solver checks calorie balance and terrain compatibility instantly — eliminating the risk of manual errors.
- Solve the Ecosystem scenario in < 10 minutes
- Instant calorie & terrain validation
- Eliminates risk of calculation errors
- Simple web interface — no download required
- Instant access
Build your understanding from scratch.
Three full Ecosystem simulations built from real past PSG data, with detailed solutions for every question.
- 3 × full Ecosystem simulations
- Real past PSG data
- Detailed solutions for every question
- Exact game replication
- Instant access
Both products are included in the Ultimate PSG Bundle — the best-value way to prepare for the full assessment.
Ecosystem FAQs
What is the McKinsey Ecosystem scenario?
The Ecosystem Builder is a simulation scenario in the McKinsey Solve assessment. You act as an environmental researcher building a sustainable food chain across a terrain: each predator must meet its calorie needs, every predator-prey pair must produce a calorie surplus, and all species must be compatible with the site conditions. It tests systemic thinking and accuracy under pressure.
What is the Ecosystem Solver?
The Ecosystem Solver is a tool that checks your food chain for calorie balance and terrain compatibility instantly, letting you solve the Ecosystem scenario in under 10 minutes and eliminating the risk of manual errors. It runs in a simple web interface with instant access and is backed by a 30-day refund guarantee.
How does the Ecosystem Solver refund guarantee work?
If you fail the Ecosystem scenario within 30 days of purchasing the Ecosystem Solver, email info@psgsolver.com with a screenshot of your result and we will refund you in full, usually within 24 hours, no questions asked. The guarantee applies specifically to the Ecosystem Solver.
Why do candidates find the Ecosystem scenario hard?
The difficulty comes from cascading constraints: one incorrect calorie calculation can invalidate the entire chain, terrain-compatibility mismatches are easy to overlook, and validating everything manually under time pressure takes longer than most candidates expect. Holding all the rules in mind at once is what makes it challenging.
How many Ecosystem practice tests does PSG Solver include?
PSG Solver includes three full Ecosystem practice tests built from real past PSG data, each replicating the live scenario with detailed solutions for every question. The optional Ecosystem Solver tool is also available, and both are included in the Ultimate PSG Bundle.