Ecological Evidence & Environmental Design — Chapter Practice, Grade 7

Five focused units, a three-session investigation, chapter review, and chapter quiz.

Problem 1

Does sharing a habitat alone prove competition?
Answer and explanation

No. Resource overlap and limitation, or effects on performance, need evidence.

Problem 2

Why might a predator not fall immediately after one prey declines?
Answer and explanation

Alternative prey, movement, stored resources, and delayed responses can affect its population.

Problem 3

What observation could strengthen a predation explanation?
Answer and explanation

Relevant feeding evidence and repeated population records, considered with alternative resources and conditions, can strengthen it.

Problem 4

Does recovery require every count to return to its original value?
Answer and explanation

Not necessarily. Recovery depends on the defined function or condition; composition and counts can differ.

Problem 5

Illustrative records show plant cover falling from 80% to 50% while herbivore count rises from 10 to 20; drought also occurs. Describe the changes, explain two plausible contributions, and propose evidence that separates them.
Answer and explanation

Herbivory could reduce cover, while drought could also limit plant growth. The two recorded changes do not isolate either cause. Compare feeding observations, water conditions, and suitable reference plots across repeated intervals. Plant cover and counts are different measures, and the model should not claim a single cause from their association alone.

Cover falls 30 percentage points.

Herbivore count doubles.

Compare feeding effects with drought and a suitable matched observation.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 6

A student labels every insect on a plant a parasite. Why is that premature?
Answer and explanation

Different insects can feed, pollinate, shelter, or interact in other ways. Identify effects and resource relationships before classifying the interaction.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 7

Which identifies competition most directly?
  1. Shared use of a limiting resource
  2. Any two different colors
  3. Every insect landing
  4. Any pair of graph axes
Answer and explanation

Shared use of a limiting resource

Competition concerns limiting-resource overlap and its effects.

Problem 8

Plant cover changes from 70% to 45%. Find the decrease in percentage points.
Answer and explanation

25 percentage points

70−45=25 percentage points, distinct from a percent decrease relative to 70.

Problem 9

Can equal individual totals have different richness?
Answer and explanation

Yes. Individuals may belong to different numbers of species.

Problem 10

Does counting species directly measure all genetic diversity?
Answer and explanation

No. Genetic variation within and among populations requires other evidence.

Problem 11

Why is diversity not a guarantee against complete habitat loss?
Answer and explanation

Varied organisms still depend on habitat and resources; a sufficiently broad disturbance can remove those conditions.

Problem 12

Why distinguish evidence from a decision criterion?
Answer and explanation

Evidence describes conditions or effects; a criterion states what the decision seeks to achieve or prioritize.

Problem 13

Illustrative equal-effort samples: A has species counts 8,1,1; B has 4,3,3. Both samples include ten individuals and three detected species. Compare richness, total abundance, and distribution without claiming one number proves universal stability.
Answer and explanation

The samples have equal richness and total count but different distributions. B is more even under the stated observations. These facts do not establish every functional relationship, genetic diversity, or response to future disturbances. Comparable repeated surveys and role-specific evidence would improve a resilience argument.

Richness is three in each.

Total abundance is ten in each.

A is more dominated by one species; B is more evenly distributed.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 14

A longer survey finds more species than a shorter one. Must true biodiversity have increased?
Answer and explanation

No. Greater detection effort can reveal previously missed species. Standardize effort before interpreting it as a biological change.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 15

Which sample has greater observed richness?
  1. Ten of one species
  2. Ten distributed across four species
  3. Both must equal ten species
  4. Neither can be counted
Answer and explanation

Ten distributed across four species

Four detected species is greater richness than one, even with equal individual totals.

Problem 16

A survey detects two plant, three insect, and one bird species with no overlap. Find observed richness.
Answer and explanation

6 species

2+3+1=6 detected species under the stated categories.

Problem 17

Why does a mapped barrier not prove an exact population loss?
Answer and explanation

Actual effects depend on movement, species needs, alternative routes, and observations not given by the line alone.

Problem 18

Does clearer water prove every contaminant is absent?
Answer and explanation

No. Some dissolved substances or organisms are not revealed by clarity alone.

Problem 19

Why distinguish planted area from surviving cover?
Answer and explanation

Planting is an action; later survival and cover are outcomes requiring observations.

Problem 20

Can two different recommendations both be well supported?
Answer and explanation

Yes, if they use evidence accurately, state criteria and constraints, and explain tradeoffs and uncertainty.

Problem 21

Illustrative matched-rain model: Area A sends 18 L to surface runoff and Area B 10 L after a vegetation treatment. Starting conditions are stated comparable, but only one trial is supplied. Calculate the difference, explain a plausible pathway, and qualify a universal water-quality claim.
Answer and explanation

B has 8 L less recorded runoff in this illustrative trial. Vegetation-associated retention or infiltration could contribute under the stated comparison. The record does not establish all causal details, repeated performance, or absence of contaminants. More matched trials and separate water-quality measures are needed for stronger claims.

Difference: 18−10=8 L.

Connect vegetation and soil with possible infiltration or retention.

Separate runoff amount from all water-quality properties and identify the single-trial limit.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 22

A project reports 100 planted seedlings. What should be measured before claiming habitat function was restored?
Answer and explanation

Survival, developing cover, relevant species use, and defined ecosystem functions over time would test outcomes beyond the initial planting count.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 23

Which is an outcome rather than only an activity count?
  1. Number planted on day one
  2. Surviving cover after a defined interval
  3. Number of notices printed
  4. Project name
Answer and explanation

Surviving cover after a defined interval

Surviving cover measures a later result, while initial planting is an action count.

Problem 24

A model receives 30 L rain input and has 9 L runoff. What percent becomes recorded runoff?
Answer and explanation

30 %

9/30×100=30% under the stated boundary and interval.

Problem 25

Why specify whether sightings or individuals are counted?
Answer and explanation

Repeated sightings can involve one individual; the quantities answer different questions.

Problem 26

Can a mean remove biased site selection?
Answer and explanation

No. A biased set can still produce a precise-looking mean; location selection must be addressed.

Problem 27

Why can equal plot counts differ in density?
Answer and explanation

Plot areas can differ; count per area accounts for that boundary.

Problem 28

Does sample density establish the exact habitat total?
Answer and explanation

No. Extrapolation depends on sample representativeness, area definitions, and detection.

Problem 29

Illustrative four 1 m² plots contain 2, 4, 3, and 3 plants of one species. A habitat area is 20 m². Find sample density, calculate an extrapolated count, and state the assumptions that prevent calling it a complete census.
Answer and explanation

The sample density is 3 plants/m² and the extrapolated count is 60 plants. It is an estimate assuming the plots represent the 20 m² habitat and detection is adequate. Patchiness, omitted zones, or missed plants could change the result. The supplied data do not establish an exact total.

Total count: 12 across 4 m².

Density: 12/4=3 plants/m².

Estimated larger count: 3×20=60.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 30

A team uses four 1 m² plots in one habitat and four 2 m² plots in another. Can mean counts alone compare density?
Answer and explanation

No. Different plot areas require count-per-area calculations or an appropriately weighted comparison using comparable detection methods.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 31

Which choice reduces the stated location-selection problem?
  1. Only sample favorite patches
  2. Use a predefined representative location plan
  3. Delete low counts
  4. Change plot size secretly
Answer and explanation

Use a predefined representative location plan

A planned sampling method helps address selection bias, though other limits remain.

Problem 32

A survey detects 18 plants across 6 m². Find density.
Answer and explanation

3 plants/m²

18/6=3 plants/m² under the stated detection method.

Problem 33

How is a criterion different from a constraint?
Answer and explanation

A criterion evaluates success; a constraint limits allowable options, such as a maximum budget or available area.

Problem 34

Why not compare one design’s best trial with another’s worst?
Answer and explanation

It selects evidence unfairly and can misrepresent typical performance; compare the full relevant records.

Problem 35

Does a lower-cost design automatically win?
Answer and explanation

No. Cost is one criterion and feasibility limit; outcomes and other requirements also matter.

Problem 36

What makes a proposed revision useful?
Answer and explanation

It targets an identified limitation or tradeoff and can be evaluated with a defined measurement.

Problem 37

Illustrative plans within a 100-token budget: A costs 80 and reduces runoff from 20 to 8 L; B costs 60 and reduces it from 20 to 10 L. Both satisfy the same stated space requirement; later maintenance is unknown. Calculate reductions, compare reduction per token, and recommend a feasible option under an explicit criterion with a next test.
Answer and explanation

A provides the larger total reduction in the model, while B gives a slightly larger reduction per token. Both fit the initial budget. Either can be supported under an explicit priority, but maintenance, repeated performance, and real-setting transfer remain unknown. Recommend a matched repeated test and a maintenance estimate; fictional tokens are not actual prices.

A reduction: 12 L; B: 10 L.

A ratio: 12/80=0.15 L/token; B: 10/60≈0.167 L/token.

Choose using total reduction or cost efficiency and identify maintenance uncertainty.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 38

Plan C achieves the largest reduction but costs 130 tokens under the same 100-token limit. Is it currently feasible?
Answer and explanation

No. It exceeds the stated constraint unless the budget or plan changes. A desirable result does not remove a feasibility limit.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 39

Which is a constraint?
  1. Maximum budget of 100 tokens
  2. Wanting more cover
  3. Liking a color
  4. A general hope
Answer and explanation

Maximum budget of 100 tokens

The budget limits feasible options; criteria measure desired performance.

Problem 40

A model runoff falls from 24 L to 9 L. Find reduction.
Answer and explanation

15 L

24−9=15 L under the supplied comparison.

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