Predator-Prey Relationships

This relationship helps keep stability in ecosystems regulating population sizes and the matter cycle. Invasive species can hurt ecosystems if they have no predators.

Key terms:

  • Carrying Capacity – maximum number possible of individuals in a species that the ecosystem can support indefinitely with its resources.
  • Invasive Species – non-native organism that spreads widely in a community due to a lack of predators.

Characteristics of a healthy ecosystem:


The size of a group decreases as you go up because more prey is needed than predators to keep the ecosystem balanced.

Populations are kept in check by their predators.



Ecosystems with invasive species:

  • No predators for invasive species lead to an unstable ecosystem. Unstable because of having large populations they will consume all available resources. This leads to less resources for native species.
  • Example: rabbits in Australia
    • no natural predator there, so they ate all the resources endangering native species.