Disturbance, Interactions & Ecosystem Change — Practice · Grade 10 Science

Chapter: Ecosystems & Conservation Decisions

What this practice covers

By the end of Disturbance, Interactions & Ecosystem Change you should be able to:

8 questions, numeric, multiple choice and written answer, each with a worked explanation.

Vocabulary used: disturbance, resistance, succession.

Problem 1

Cover falls from 60% to 30%. What is the decrease in percentage points?
Answer and explanation

30 percentage points

60 − 30 = 30; this differs from percent reduction.

Problem 2

Which evidence best tests a recovery claim?
  1. A time series and suitable comparison sites
  2. Only one decorative photo
  3. The species name alone
  4. A guaranteed endpoint
Answer and explanation

A time series and suitable comparison sites

Repeated and comparison evidence helps separate recovery from other changes.

Problem 3

Why might removing a predator affect plants?
Answer and explanation

Changes in herbivores can alter grazing, but other interactions may modify the response.

Problem 4

After a flood, species richness returns but nutrient retention remains low. Has every function recovered? Explain the reasoning in your own words.
Answer and explanation

No; different indicators reveal different aspects of recovery.

Richness is one structural indicator.

Nutrient retention measures a different function and remains altered.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 5

A predator decline precedes heavier grazing. What causal evidence would strengthen a food-web explanation? Show the reasoning, not just the conclusion.
Hints

Define recovery operationally instead of assuming one universal measure.

Answer and explanation

Repeated abundance and feeding data, comparisons and mechanisms that rule out alternative resource or climate changes.

Problem 6

Why can two disturbances close together impede recovery more than one?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

The second may arrive before populations, soils or resources recover, altering thresholds and trajectories.

Problem 7

Resistance and recovery describe different parts of a responseResistance and recovery describe different parts of a responseSelected system output index025507510001234Years around disturbanceA: large change / fast recoveryB: small change / slow recovery
Original resistance/recovery comparison with arbitrary output indices, not complete ecosystem restoration evidence.
Interpret the supplied visual. Which supplied model has lower resistance but faster recovery?
Answer and explanation

A changes from 100 to 20, then returns to 100 by year four; B changes less but has not returned in that interval.

Resistance describes how little a system changes during a specified disturbance. Recovery describes return of selected properties afterward. Resilience is used in several related ways, so define the sense and measured variable before comparing systems. A system can change strongly yet recover rapidly, while another changes little but recovers slowly. Returning one output to baseline does not guarantee identical species composition or restored every function. Compare reference variability and the time interval rather than rank ecosystems by one undefined resilience label.

A changes from 100 to 20, then returns to 100 by year four; B changes less but has not returned in that interval.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

Problem 8

A supplied system loses 80% of its output during disturbance and returns to its initial output after three years. Describe resistance and recovery and explain one limit of that evidence.
Answer and explanation

It has low resistance for this disturbance/output but relatively rapid recovery over the stated interval. Output recovery alone does not establish restored species composition or every ecological function.

It has low resistance for this disturbance/output but relatively rapid recovery over the stated interval. Output recovery alone does not establish restored species composition or every ecological function.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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