Human Impact & Stewardship — Practice · Grade 9 Science

Chapter: Resources & Human Decisions

What this practice covers

By the end of Human Impact & Stewardship you should be able to:

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

Vocabulary used: stewardship, sustainability, conservation, per-capita consumption.

Problem 1

Total demand on Earth's resources depends on which two factors multiplied together?
  1. Population size and per-capita consumption
  2. Ocean temperature and rainfall
  3. Number of countries and number of languages
  4. Distance from the equator and elevation
Answer and explanation

Population size and per-capita consumption

Total resource demand equals population size multiplied by how much each person consumes on average.

Problem 2

Which best defines 'stewardship'?
  1. Extracting as many resources as possible as fast as possible
  2. Managing and using resources responsibly so future generations can meet their needs too
  3. Ignoring environmental impact to boost the economy
  4. Only ever using nonrenewable resources
Answer and explanation

Managing and using resources responsibly so future generations can meet their needs too

Stewardship means taking responsible care of resources so they remain available for the future.

Problem 3

A town's population grows from 5,000 to 15,000 people, while per-capita use stays the same. By what factor does total resource demand increase?
Answer and explanation

3 ×

15,000 ÷ 5,000 = 3, so demand triples even with the same per-capita use.

Problem 4

A city's population grows by a factor of 1.5, and per-capita electricity use grows by a factor of 2. By what overall factor does total electricity demand increase?
Answer and explanation

3 ×

Multiply the two factors together: 1.5 × 2 = 3× the total demand.

Problem 5

Which of these is the BEST example of a stewardship strategy?
  1. Setting fishing quotas so fish populations can regrow before more are caught
  2. Draining a wetland to build a parking lot
  3. Pumping groundwater as fast as possible for a new water park
  4. Burning coal without any pollution controls
Answer and explanation

Setting fishing quotas so fish populations can regrow before more are caught

Fishing quotas let a population regrow, which is a sustainable, responsible way to manage a resource.

Problem 6

Explain, using the idea of per-capita consumption, why a small increase in population combined with a big increase in per-person resource use can strain Earth's systems even more than a huge population increase with no change in per-person use.
Answer and explanation

Because total demand is population multiplied by per-capita use, a big jump in per-capita consumption multiplies across the whole population, so even a modest population increase combined with people each using much more can produce a bigger total increase in demand than population alone growing a lot while individual use stays the same.

Problem 7

A stream becomes clearer after planting a buffer, but rainfall also fell. What limits the causal claim? Explain the reasoning in your own words.
Answer and explanation

The result is consistent with improvement but does not isolate the buffer's effect.

Both planting and rainfall changes could affect sediment.

Compare similar untreated areas and repeated measurements under comparable weather.

Response criteria

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

Problem 8

Why can fertilizer runoff affect dissolved oxygen? Show the reasoning, not just the conclusion.
Hints

A before–after change alone is not a controlled causal test.

Answer and explanation

Nutrients can stimulate growth, followed by decomposition that consumes oxygen, depending on conditions.

Problem 9

A clean-energy project reduces emissions but damages habitat. What should evaluation include?
Hints

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

Answer and explanation

Both climate benefit and habitat impact, with alternatives, equivalent service, uncertainty and monitoring.

Problem 10

Preventing input and restoring function are distinct goalsPreventing input and restoring function are distinct goalsSeparate supplied outcome indicesInitial pollutant input100After prevention70Reduction pathway75Later restorationindicator60Specify which input, exposure or ecosystem function each action targets.
Original conceptual intervention-outcome indices, not a measured restoration trial or one-unit ranking of alternatives. The distinct indices are not additive and cannot establish total ecological benefit without defined criteria and a common comparison basis.
Interpret the supplied visual model. Why is the number of planted trees insufficient evidence that an ecosystem has recovered?
Answer and explanation

It measures an action. Survival, appropriate species, biodiversity, soil/habitat functions and other goal-linked outcomes need monitoring over time.

Read the bars as separately defined illustrative indicators, not identical physical quantities. Their labels identify which part of the intervention chain is being assessed.

It measures an action. Survival, appropriate species, biodiversity, soil/habitat functions and other goal-linked outcomes need monitoring over time.

Response criteria

  • Read the labeled quantities, reference frame or objects correctly.
  • Explain the relation between the visual evidence and the mechanism.
  • Keep the drawing’s stated assumptions and limits in the conclusion.

Problem 11

Population rises 20% while average use/person falls 10%. Calculate the total-demand factor and explain one limit of using the average to describe impacts on all families.
Answer and explanation

1.20×0.90 = 1.08, an 8% total rise. A population average hides differences in use, access and circumstances; it does not establish identical individual consumption or responsibility.

Convert changes to factors 1.20 and 0.90.

Multiply to get 1.08, an 8% rise.

Identify the aggregation limit and ask for group-specific evidence when relevant.

Response criteria

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

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