Ecosystems

Ecosystem Basics

• Individual: one organism (example: elk).

• Population (Pop.): group of individuals of the same species (example: elk herd).

• Community: all living organisms in an area.

• Ecosystem: all living and nonliving things in an area (plants, animals, rocks, soil, water, air).

• Biome: a large area with similar climate conditions that determine which plant and animal species occur there (example: tropical rainforest).

Organism Interactions

• Mutualism: a relationship that benefits both organisms (example: coral reef community).

• Competition: organisms fighting over a resource (e.g., food or shelter); limits population size.

• Predation: one organism using another as an energy source (examples: hunters, parasites, even herbivores).

• Commensalism: a relationship that benefits one organism and does not impact the other (example: birds nesting in trees).

Predation and Predator-Prey Roles

• Predation categories:

  • True predators: carnivores that kill and eat prey for energy (example: leopard).

  • Herbivores: plant eaters that obtain energy from plants (example: giraffe feeding on trees).

  • Parasites: use a host organism for energy, often without killing the host, and often living inside the host (examples: mosquitoes, tapeworms, sea lamprey).

  • Parasitoids: lay eggs inside a host; eggs hatch and larvae eat the host for energy (examples: parasitic wasps, bot fly).

Symbiosis

• Etymology: sym = together; bio = living; osis = condition.

• Symbiotic relationships: mutualism (+/+), commensalism (+/0), and parasitism (+/-).

• Mutualism example: Coral (animals) provide reef structure and CO2 for algae; algae provide sugars for coral to use as energy.

• Lichen: composite organism consisting of fungi living with algae; algae provide sugars (energy) and fungi provide nutrients.

Competition and Resource Partitioning

• Resource partitioning: different species using the same resource in different ways to reduce competition.

  • Reduces population size because there are fewer resources available and fewer organisms can survive.

• Temporal partitioning: using a resource at different times (example: wolves & coyotes hunting at different times — night vs. day).

• Spatial partitioning: using different areas of a shared habitat (differences in root length, etc.).

• Morphological partitioning: using different resources based on evolved body features.

• No two species can occupy the same niche — Competitive Exclusion Principle.

Keystone Species

• Keystone species: a species that plays a role in its community far more important than its relative abundance might suggest.

Practice FRQ 1.1

• Prompt: Identify two organisms that compete for a shared food resource. Describe how resource partitioning could reduce the competition between the two organisms you identified.

• Suggested example (aligned with course content):

  • Organisms: wolves and coyotes.

  • Shared resource: small mammals or other prey in overlapping habitats.

  • Resource partitioning to reduce competition:

  • Temporal partitioning: wolves hunt primarily at night, while coyotes may hunt more during twilight or day in some contexts.

  • Spatial partitioning: wolves may operate in different microhabitats or territories where available prey differ in density or type.

  • Morphological partitioning: wolves and coyotes may specialize on different prey sizes or types due to differences in dentition and body size.

• This demonstrates how resource partitioning can lessen direct competition and allow coexistence of both species despite overlapping diets.

Ecosystems

Ecosystem Basics

• Individual: single organism (e.g., elk).

• Population (Pop.): group of same species (e.g., elk herd).

• Community: all living organisms in an area.

• Ecosystem: all living and nonliving components.

• Biome: large area with similar climate and species.

Organism Interactions

• Mutualism: both organisms benefit (e.g., coral reef).

• Competition: organisms fight for resources; limits population.

• Predation: one organism uses another for energy (e.g., hunters, parasites, herbivores).

• Commensalism: one benefits, other unaffected (e.g., birds in trees).

Predation and Predator-Prey Roles

• Predation categories:

  • True predators: kill and eat prey (e.g., leopard).

  • Herbivores: eat plants for energy (e.g., giraffe).

  • Parasites: use a host for energy, often inside, without killing (e.g., mosquitoes, tapeworms).

  • Parasitoids: lay eggs in host; larvae eat host (e.g., parasitic wasps).

Symbiosis

• Etymology: sym = together; bio = living; osis = condition.

• Symbiotic relationships: mutualism (+/+), commensalism (+/0), parasitism (+/-).

• Mutualism example: Coral provides structure/CO2 for algae; algae provide sugars for coral.

• Lichen: fungi with algae; algae provide energy, fungi provide nutrients.

Competition and Resource Partitioning

• Resource partitioning: species use same resource differently to reduce competition.

  • Reduces population size due to fewer available resources.

• Temporal partitioning: using resources at different times (e.g., wolves & coyotes hunt night vs. day).

• Spatial partitioning: using different areas of a shared habitat (e.g., root lengths).

• Morphological partitioning: using different resources based on evolved features.

• Competitive Exclusion Principle: No two species can occupy same niche.

Keystone Species

• Keystone species: plays a disproportionately important role in its community.

Practice FRQ 1.1

• Prompt: Identify two competing organisms and describe how resource partitioning reduces competition.

• Example:

  • Organisms: wolves and coyotes.

  • Shared resource: small mammals in overlapping habitats.

  • Resource partitioning examples:

    • Temporal: wolves hunt mainly at night; coyotes hunt more during twilight/day.

    • Spatial: wolves use different microhabitats/territories for prey.

    • Morphological: wolves/coyotes specialize on different prey sizes/types.

• This shows how resource partitioning allows coexistence despite overlapping diets.