Populations & Communities — Drills · Grade 10 Science

Chapter: Ecosystems & Conservation Decisions

What these drills covers

By the end of Populations & Communities you should be able to:

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

Vocabulary used: population, exponential growth, logistic growth, carrying capacity, limiting factor, symbiosis.

Problem 1

The maximum population size an environment can sustain with its available resources is its
  1. biotic potential
  2. carrying capacity
  3. trophic level
  4. niche
Answer and explanation

carrying capacity

Carrying capacity is set by the supply of limiting resources; a population above it declines.

Problem 2

A population grows from 120 to 150 individuals in one year. What is the percentage increase?
Answer and explanation

25 %

(150 − 120) / 120 × 100 = 25 percent.

Problem 3

Which is a density-dependent limiting factor?
  1. A late frost
  2. A flood
  3. Competition for food within the population
  4. A volcanic eruption
Answer and explanation

Competition for food within the population

Competition intensifies as density rises, so its effect depends on population size. Weather and geological events act regardless of density.

Problem 4

A population of 2,000 deer occupies 50 square kilometres. What is the population density in deer per square kilometre?
Answer and explanation

40 per km²

2,000 / 50 = 40 deer per square kilometre.

Problem 5

Distinguish exponential from logistic growth and state which is sustainable in a closed environment.
Answer and explanation

Exponential growth means the population increases by a constant proportion each interval, so numbers rise ever more steeply with no limit. Logistic growth begins in the same way but slows as the population approaches carrying capacity, levelling off when resource limits take effect. Only logistic growth is sustainable in a closed environment, because exponential growth necessarily exceeds any finite resource supply and ends in a crash.

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

Name three types of symbiosis and state who benefits in each.
Answer and explanation

In mutualism both species benefit, as when a pollinator feeds and the plant is pollinated. In commensalism one benefits and the other is largely unaffected, as when a bird nests in a tree. In parasitism one benefits at the other's expense, as when a tapeworm absorbs nutrients from a host. The classification depends on measured effects on survival or reproduction, not on appearances, and the same pair can shift category as conditions change.

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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