Biodiversity, Variation & Ecosystem Resilience — Practice · Grade 7 Science

Chapter: Ecological Evidence & Environmental Design

What this practice covers

By the end of Biodiversity, Variation & Ecosystem Resilience you should be able to:

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

Vocabulary used: biodiversity, species richness, abundance, evenness, resilience.

Problem 1

Can equal individual totals have different richness?
Answer and explanation

Yes. Individuals may belong to different numbers of species.

Problem 2

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

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

Problem 3

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 4

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 5

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 6

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 7

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 8

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.

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