Biodiversity Loss — Drills · Grade 12 Science

Chapter: Conservation, Systems & Environmental Design

What these drills covers

By the end of Biodiversity Loss you should be able to:

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

Vocabulary used: biodiversity, extinction, habitat fragmentation, invasive species, ecosystem services.

Problem 1

Which of the following best describes biodiversity?
  1. The total number of animals kept in a zoo
  2. Only the largest predators in an ecosystem
  3. The amount of rainfall a region receives
  4. The variety of life — the genes, species, and ecosystems in an area
Answer and explanation

The variety of life — the genes, species, and ecosystems in an area

Biodiversity spans three levels: genetic variety within species, the number of different species, and the range of ecosystems.

Problem 2

Which of these is an example of an invasive-species problem?
  1. Burmese pythons multiplying in the Florida Everglades, where they have no natural predators
  2. A farmer planting a field of corn
  3. A wolf hunting deer in its native range
  4. A native oak growing in its home forest
Answer and explanation

Burmese pythons multiplying in the Florida Everglades, where they have no natural predators

The pythons are non-native and spread unchecked because their new range lacks the predators and competitors that limited them back home — the definition of an invasive species.

Problem 3

A native prairie covering 1,200 hectares is plowed and developed until only 300 hectares remain. What percentage of the original prairie habitat was lost?
Answer and explanation

75 %

Area lost = 1,200 - 300 = 900 hectares; 900 ÷ 1,200 = 0.75, or 75% lost.

Problem 4

Explain why extinction is considered a more serious environmental problem than many others, such as air pollution.
Answer and explanation

Most environmental problems can be reversed — polluted air and water can be cleaned, and a warmed climate could eventually cool. Extinction is permanent: once the last members of a species die, that species and its unique genes and ecological role are gone forever and cannot be brought back. That irreversibility is what makes biodiversity loss especially serious.

Problem 5

Which of these is an ecosystem service provided by biodiversity?
  1. The construction of highways
  2. The pollination of food crops by insects
  3. The mining of coal from the ground
  4. The manufacture of plastic bottles
Answer and explanation

The pollination of food crops by insects

Pollination by insects is a free service that biodiverse ecosystems provide, supporting about a third of the crops we eat; the other choices are human industrial activities, not ecosystem services.

Problem 6

Explain why breaking a habitat into small, isolated patches (fragmentation) can reduce biodiversity even if the total protected area stays the same.
Answer and explanation

Fragmentation isolates populations so they can't interbreed, reducing genetic diversity and making local extinctions more likely. Small patches may be too small for wide-ranging or large species, and dividing a habitat creates more edge, exposing the interior to drying, predators, and invasive species. So the same total area, once fragmented, supports fewer species than it would if kept as one connected block.

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