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Ecosystem Dynamics - Study Guide

Ecosystem Basics

  • Ecosystem: All the interacting biotic (living) and abiotic (non-living) factors in a specific area at a specific time.

Levels of Organization

  • Species: A group of organisms that can interbreed.
  • Population: Members of the same species in one area.
  • Community: All the different populations in one area.
  • Ecosystem: The community plus abiotic factors.
  • Habitat: The physical environment where organisms live.

Examples

  • Biotic factors: Plants, animals, fungi, bacteria.
  • Abiotic factors: Sunlight, temperature, water, soil, air.

Ecosystem Roles

  • Producers (Autotrophs): Use sunlight to make food (e.g. plants).
  • Consumers (Heterotrophs): Eat other organisms.
    • Primary consumers: Herbivores (e.g. rabbit).
    • Secondary consumers: Carnivores that eat herbivores (e.g. snake).
    • Tertiary consumers: Eat secondary consumers (e.g. hawk).
    • Quaternary consumers: Top predators (e.g. killer whale).
  • Omnivores: Eat plants and animals (e.g. humans, bears).
  • Decomposers: Break down dead material at the molecular level (e.g. bacteria, fungi).
  • Detritivores: Eat dead material in chunks (e.g. worms).

Energy Flow in Ecosystems

  • 1st Law of Thermodynamics: Energy can't be created or destroyed, only changed.
  • 2nd Law of Thermodynamics: Each energy transfer loses usable energy (often as heat).

Ecological Pyramid

  • Energy decreases as you move up trophic levels.
  • Only about 10% of energy transfers to the next level.

Energy Use Breakdown

  • 17% growth (passed on).
  • 50% waste.
  • 33% cellular respiration (lost as heat).

Food Chains vs. Food Webs

  • Food Chain: Single path of energy.
  • Food Web: Interconnected food chains, more realistic representation.

Humans in Food Chains

  • Eating plants (vegetarian) = more energy efficient.
  • Eating animals = higher energy loss.

Biodiversity

  • Definition: Variety of life in all forms, levels, and combinations.

Types of Biodiversity

  • Species Diversity: Number and balance of species.
  • Genetic Diversity: Variety of genes within a species.
  • Ecological Diversity: Variety of ecosystems, niches, trophic levels.

Importance of Biodiversity

  • Supports ecosystem homeostasis (balance).
  • Provides food, medicine, clean water, air, pollination, etc.
  • More diversity = more resilience to change or disturbance.

Ecosystem Services

  • Provisioning: Food, water, medicine.
  • Regulating: Air quality, climate, disease.
  • Supporting: Nutrient cycling, pollination, soil formation.
  • Cultural: Recreation, spiritual value.

Human Impact & Tragedy of the Commons

  • Tragedy of the Commons: Shared resources overused for short-term personal gain, causing long-term loss for all.
    • Example: Overfishing.
    • Solution: Cooperation, limits, and sustainable practices.

Carrying Capacity

  • Maximum population size an ecosystem can support without degrading the environment.

Human Impacts on Ecosystems

  • Habitat destruction.
  • Overhunting/fishing.
  • Pollution and chemical use.
  • Invasive species.
  • Climate change.