Ecology Week 1 Notes

Ecology Week 1

Basic Ecological Principles

Event Guidelines (Ecology C Science Olympiad)

• Participants: Teams of up to 2 students

• Calculator: Class II, non-programmable, non-graphing

• Duration: Approx. 50 minutes

Event Structure

1. Assessment Components (equal point value)

   • General Principles of Ecology

   • Terrestrial Ecosystems

   • Human Impact on Ecosystems

Part 1: Review of the General Principles of Ecology

• Focus Areas:

  • Food webs and trophic pyramids

  • Nutrient cycling

  • Community interactions

  • Population dynamics (density-dependent/independent factors, carrying capacity)

  • Extinction, selection, migration

  • Local/regional ecological principles

Part 2: Terrestrial Ecosystems

• Key Concepts:

  • Biodiversity and its importance

  • State/National events: Apply knowledge of biodiversity (maps, simulations)

  • Understand species richness calculations (Simpson index, Shannon-Wiener index)

Part 3: Human Impact on Ecosystems

• Topics:

  • Climate change, invasive species, acid deposition

  • Pros and cons of alternative energy

  • Conservation biology goals

  • Reclamation vs. reintroduction of species

  • Incorporating Indigenous knowledge and traditional ecological knowledge (TEK)

Ecological Levels of Organization

• Definitions:

  1. Organism: Individual of a species

  2. Population: Group of the same species

  3. Community: Multiple populations of different species

  4. Ecosystem: Community + environment (biotic/abiotic)

  5. Biome: Group of ecosystems with specific climate

  6. Biosphere: Earth system containing all biomes

Trophic Levels

• Levels of a food web:

  1. Primary producers (1st level, high population)

  2. Primary consumers (2nd level)

  3. Secondary consumers (3rd level)

  4. Tertiary consumers (4th level)

  5. Apex predators (5th level, low population)

• Energy Transfer: Only 10% transfer from one level to the next (90% lost as heat)

Trophic Cascades

• Types:

  • Top-bottom cascade: higher levels affect lower levels

  • Bottom-up cascade: lower levels affect higher levels

  • Subsidy cascade: organisms crossing community boundaries affecting ecosystems

Population Distribution

• Patterns:

  • Clumped: Patchy resources

  • Uniform: Competing for scarce resources

  • Random: Minimal interaction with others

Population Density

• Concepts:

  • Density-dependent factors: Vary by population size (e.g., disease)

  • Density-independent factors: Same effect regardless of population size (e.g., natural disasters)

Age Structure

• Categories:

  • Rapid growth: High juveniles, low adults/seniors

  • Slow growth: High juveniles, medium adults, low seniors

  • Stable: High juveniles/adults, medium seniors

  • Declining: Low juveniles, high adults, medium seniors

Survivorship Curves

• Types:

  1. Type 1: High survivorship (humans)

  2. Type 2: Constant mortality rate (rodents)

  3. Type 3: High young mortality (fish)

Species Interactions

• Types of Relationships:

  • Mutualism: Both benefit

  • Commensalism: One benefits, other unaffected

  • Parasitism: One benefits, other harmed

  • Competition: Species compete for resources

  • Predation: One preys on another

Tragedy of the Commons

• Concept:

  • Common resources can be overused, degrading the land

  • Use should stay below carrying capacity

  • Increased use leads to degradation affecting all users

Types of Organisms

• Groups:

  • Autotrophs: Produce own energy

  • Heterotrophs: Consume other organisms

  • Decomposers: Break down organic matter

    • Detritivores: Consume detritus

    • Saprotrophs: Use external processes to break down organic matter

  • Scavengers: Consume dead organisms

Ecological Niches

• Concepts:

  • Niche: Role of organism in ecosystem

  • Keystone species: Unique role that supports ecosystem

  • Ecosystem engineers: Create habitats

  • Invasive species: Compete for resources, outcompete natives

  • Indicator species: Reflect environmental changes

  • Competitive exclusion principle: Similar species cannot coexist perfectly

Succession

• Types:

  • Primary succession: Development on barren land

  • Secondary succession: Development after disturbance

Population Growth Models

• Patterns:

  • Exponential Growth: Rapid increase over time

  • Logistic Growth: Growth limited by carrying capacity

r/K Selection Theory

• r-selection: Fast reproduction, early maturity (e.g., birds, insects)

• k-selection: Slow reproduction, focus on growth (e.g., mammals)

• Examples: Sea turtles show both traits.