Chapter 4: Community & Population Ecology and Human Population


What Roles Do Species Play in an Ecosystem?

  • Each species plays a role in its ecosystem
    • The distinct role is its ecological niche.
    • Includes everything that affects its survival and reproduction, such as:
    • Niche differs from habitat.
    • Niche Types
      • Generalist species:
        • include:
          • flies
          • cockroaches
          • mice rats
          • white-tailed deer
          • raccoons
          • humans
      • Specialist species:
        • For Example, some shorebirds occupy specialized niches, feeding on food found only along sandy beaches and wetlands
      • Is it better to be a generalist or specialist?
        • It depends.....
          • When environmental conditions are stable, as in a tropical rainforest, specialists have an advantage because they have fewer competitors


Niches Can Be Occupied by Native and Nonnative Species

  • Niches can be classified further in terms of specific roles the certain species play:
    • native species: normally live and thrive in an ecosystem
    • nonnative species: migrate into or are deliberately or accidentally introduced into an ecosystem. Also known as invasive, alien and exotic species.
    • indicator species: serve as biological smoke alarms. Provide early warnings of damage to an ecosystem. Examples include:
      • butterflies
      • some amphibians
      • canaries in mines
    • keystone species: have a large effect on the types and abundance of other species in an ecosystem
    • foundation species: create and enhance their habitats in ways that benefit other species

Reintroduction of Wolves to Yellowstone NP


How Do Species Interact?

Zebra mussels

What Factors Influence the Size of the Human Population?

PowerPoint Slides

Biodiversity Decline (The Habitable Planet)