Human Impact & Conservation — Drills · Grade 10 Science

Chapter: Ecosystems & Conservation Decisions

What these drills covers

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

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

Vocabulary used: biodiversity, greenhouse gas, habitat fragmentation, invasive species, sustainability, conservation.

Problem 1

Habitat fragmentation differs from habitat loss in that fragmentation
  1. removes all habitat
  2. divides remaining habitat into smaller separated pieces
  3. only affects plants
  4. increases total habitat area
Answer and explanation

divides remaining habitat into smaller separated pieces

Fragmentation breaks habitat into isolated patches, which reduces movement between populations and raises the proportion of edge relative to interior.

Problem 2

An invasive species often spreads rapidly in a new area because
  1. it reproduces more slowly
  2. its usual predators, parasites, and competitors are absent
  3. it needs no resources
  4. it cannot reproduce
Answer and explanation

its usual predators, parasites, and competitors are absent

Released from the species that limited it in its native range, an introduced population can grow quickly and outcompete local species.

Problem 3

A forest of 1,200 hectares is reduced to 340 hectares. What percentage has been lost?
Answer and explanation

71.7 %

(1,200 − 340) / 1,200 × 100 ≈ 71.7 percent lost.

Problem 4

A fish stock is estimated at 90,000 t and the annual catch is 27,000 t. What percentage of the stock is taken each year?
Answer and explanation

30 %

27,000 / 90,000 × 100 = 30 percent, which exceeds most sustainable harvest rates and would be expected to reduce the stock.

Problem 5

Explain why protecting a single large area is often more effective than protecting several small areas of the same total size.
Answer and explanation

A large area holds larger populations, which are less vulnerable to chance extinction and to the loss of genetic variation through drift. It also has a smaller proportion of edge relative to interior, so conditions suited to interior species are preserved. Several small patches of the same total area support smaller, more isolated populations with less gene flow between them. The advantage is not absolute, however: separate patches can protect against a single catastrophe affecting everything at once, so the best design depends on the species and the threats.

Response criteria

  • State a biologically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

Problem 6

A conservation measure is proposed. Name three kinds of evidence that should accompany it.
Answer and explanation

A baseline measurement of the population or habitat before the measure, so change can be detected; a comparison area or period that does not receive the measure, so the change can be attributed to it rather than to a general trend; and a stated monitoring plan with the indicator to be measured, the interval, and the result that would count as failure. Without these, a measure can be adopted and continued without anyone knowing whether it works.

Response criteria

  • State a biologically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

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