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.