1511-Ch41-CommEcol

Chapter 41: Community Ecology

41.1 Factors That Shape Communities

  • Biological Community: Defined as all the populations of all species living in a particular place at the same time.

41.2 Types of Species Interactions Within Communities

  • Interactions Table:

    • Commensalism:

      • Effect on Species 1: Helpful

      • Effect on Species 2: None

    • Mutualism:

      • Effect on Species 1: Helpful

      • Effect on Species 2: Helpful

    • Interspecific competition:

      • Effect on Species 1: Harmful

      • Effect on Species 2: Harmful

    • Predation, herbivory, parasitism, parasitoidism:

      • Effect on Species 1: Helpful

      • Effect on Species 2: Harmful

41.3 Long-Term Species Interactions

  • Symbiosis: Close association between two species; types include:

    • Commensal: One benefits, the other is neither helped nor harmed.

    • Mutualistic: Both species benefit.

    • Parasitic: One benefits at the expense of the other.

41.4 Mutualism

  • Definition: Interaction where both species benefit from the relationship.

    • Examples:

      • Pollinators obtaining nectar while transferring pollen for plants.

      • Nitrogen-fixing bacteria providing nitrogen to plants.

      • Mycorrhizal fungi enhancing plant mineral uptake.

41.5 Interspecific Competition

  • Definition: Competition between different species for limited resources.

  • Types of Competition:

    • Interference Competition: One species prevents another from accessing resources.

      • Example: Scavenging species chasing away competitors from a carcass.

    • Exploitative Competition: Species reduce resources availability through consumption.

      • Example: Deer and blue jays competing for acorns.

41.6 Ecological Niche

  • Definition: The role and space an organism occupies in its environment.

    • Factors include temperature, species it eats, breeding places, and resource requirements.

    • Similar niches lead to increased competition.

41.7 Competitive Exclusion

  • Process: Intense competition for resources may lead to the extinction of one species by another.

41.8 Predation and Herbivory

  • Predation Definition: Interaction where the predator captures, kills, and eats prey.

    • Abundance of Prey: Affects predator populations and dynamics.

41.9 Predator–Prey Interactions

  • Mimicry: A species evolves to resemble another for protection.

    • Example: A harmless fly mimicking a wasp to avoid predation.

  • Camouflage: Adaptation that allows animals to blend into their environment to evade detection.

41.10 Plant–Herbivore Interactions

  • Herbivory: When animals feed on plant parts.

    • Defensive Strategies: Include physical (spines, tough leaves) and chemical (toxins) defenses against herbivory.

41.11 Parasites and Parasitoids

  • Parasitism: One organism (the parasite) feeds on another (the host) without immediately killing it.

    • Examples: Bacteria and fungi that harm host organisms.

  • Parasitoids: Insects that lay eggs in a host, causing eventual death as larvae develop.

41.12 Biological Pest Control

  • Utilization of natural predators or parasites to control pest populations.

41.13 How Communities Change Over Time

  • Primary Succession: Occurs in environments devoid of soil; e.g., after volcanic eruptions.

  • Secondary Succession: Recovery in disturbed areas where soil remains.

41.14 Pioneer Species and Ecological Succession

  • Pioneer Species: First organisms to colonize barren habitats, such as mosses and lichens.

    • Change the environment, allowing other species to follow.

41.15 Disturbance

  • Definition: Disruption of community structure, whether biotic or abiotic.

    • Intermediate Disturbance Hypothesis: Greatest species diversity occurs with moderate disturbances.

41.16 Indicator Species

  • Definition: Species that respond quickly to environmental changes, serving as early warning signs for ecosystem health.

  • Examples: Trout and lichens, sensitive to pollution.

41.17 Single-Species Effects

  • Keystone Species: Species with large effects on community structure; loss alters community dynamics.

    • Examples: Wolves, beavers, elephants.

41.18 Exotic and Endemic Species

  • Endemic Species: Evolved in a specific area and cannot be found elsewhere, often facing extinction risks.

  • Exotic Species: Translocated organisms that can disrupt native ecosystems.

41.19 Invasive Species

  • Definition: Exotic species that harm their new environment, often causing declines in native species.

    • Examples include: Kudzu, spongy moths, and nutria.