Lecture Notes on the Natural World and Ecosystems

Introduction to the Natural World

Focus on the biosphere, the region of Earth occupied by life.
The biosphere includes three spheres:
- Atmosphere: Zone of air surrounding Earth.
- Lithosphere: Earth's crust and terrestrial zone.
- Hydrosphere: Zone of water.
Abiotic components (non-living): Fire, climate, topography, sunlight, wind, and seasonality.
Biotic components (living): Include various species and organisms.

Consideration of the level of scale is essential in ecological studies.
Biosphere Level: Questions about global climate impact on life.
Ecosystem Level: Focus on interactions between species and their environment.
Species Level: Study of individual species in specific locations.

Ecosystem: A community of different species interacting with each other and their environment.
Ecosystems are stable, nutrient-cycling systems.
Population: Individuals of the same species in a specific area.
Community: Different species living together in an area.

Energy flows in a one-way path through ecosystems, starting from the sun.
Trophic Levels: Represent energy flow.
- Producers (Autotrophs): Organisms that make their own food via photosynthesis.
- Primary Consumers (Herbivores): Eat producers.
- Secondary Consumers (Carnivores): Eat primary consumers.
- Tertiary Consumers: Eat secondary consumers.
- Omnivores: Eat both plants and animals.
- Detritivores and Decomposers: Consume dead organic matter; decomposers break it down to molecular components.
Food Webs: Graphical representation of energy flow, showing how energy starts from the sun and eventually leaves the ecosystem as heat.

Energy Definition: Ability to do work.
Types of Energy:
- Kinetic Energy: Energy of motion.
- Potential Energy: Stored energy.
Forms of Energy:
- Light, heat, mechanical, nuclear, and chemical energy.
Energy Quality:
- High-Quality Energy: Concentrated, can do a lot of work (e.g., fossil fuels).
- Low-Quality Energy: Dispersed, less effective at doing work (e.g., ocean heat).

Energy flows from the sun through trophic levels and exits the ecosystem as heat.
Different energy forms and qualities contribute to how ecosystems function and sustain life.