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Science

Populations and Ecosystems

Overview

Students explore how populations of organisms grow and stabilise within ecosystems, discovering the forces that regulate population size.

Learning Objective
Students understand how population size is regulated by factors such as food, disease, and predation, and can describe what carrying capacity means.

Resources needed

  • None

Lesson stages

0 / 7 done
  1. 1 Ask: if rabbits have no predators and plenty of food, what would happen to the population? (Grow exponentially).
  2. 2 Ask: does this actually happen in nature? Why not?
  3. 3 Introduce limiting factors: food supply, disease, predation, competition for mates and space.
  4. 4 Introduce carrying capacity: the maximum population size an ecosystem can sustain.
  5. 5 Draw a population growth curve: initial exponential growth then slows then levels off at carrying capacity (S-shaped curve).
  6. 6 Discuss predator-prey cycles: wolf and deer populations oscillate together — as deer increase wolves increase; wolves reduce deer; deer fall; wolves fall; deer recover.
  7. 7 Ask: what happens to carrying capacity if a habitat is destroyed? (Decreases — fewer individuals can survive).

Tap a step to mark it as done.

Variations

  • Use population data from a real species — graph the data and identify the carrying capacity.
  • Simulate a predator-prey relationship: students play rabbits and foxes in a simple role play.
  • Discuss how invasive species disrupt population balance.
More information

Teach: population, carrying capacity, limiting factor, predator, prey, cycle, exponential, S-curve. The predator-prey oscillation is counterintuitive and needs clear visual representation.

Focus on limiting factors and carrying capacity before introducing the predator-prey population cycle.

Can students draw and label an S-shaped population growth curve? Can they explain what carrying capacity means and identify two factors that limit population growth?

Draw the S-curve and predator-prey oscillation in soil. The role play simulation requires only space and students.

Students often think populations just keep growing until they run out of resources and collapse entirely. In reality, most populations stabilise near carrying capacity through feedback mechanisms.

Population ecology underpins conservation biology, fisheries management, and understanding the impact of habitat loss.

Activity details
Secondary Medium 25 minutes no prep Whole Class, Small Group Indoor & Outdoor
Topics
Populations Ecosystems Carrying Capacity