Unit A

Topics: Energy transfer, cycles of matter, maintaining equilibrium.
Key Idea: Constant flow of energy and cycling of matter leads to a balanced state achieved through biogeochemical cycles, photosynthesis, and cellular respiration.
Learning Objectives:
- Explain the one-way flow of energy in the biosphere and the loss of stored energy as heat.
- Explain energy balance through photosynthetic, chemosynthetic, and cellular respiratory activities.
- Explain ecosystem trophic levels using food chains and food webs.
- Quantitatively explain energy flow and matter exchange in ecosystems using pyramids of numbers, biomass, and energy.

Origin: Greek words "oikos" (home) and "logos" (to study).
Definition: Study of relationships and interactions between organisms and their environment.
Components: Considers living (biotic) and non-living (abiotic) components.

Biotic factors include all living organisms, such as plants, animals, and microorganisms.
Abiotic factors include non-living components, such as sunlight, water, temperature, and soil.
Examples:
- Increase in trees in a forest affects oxygen levels.
- Removal of rocks in a desert affects rock-dwelling lizards and their predators.

Composed of three structural parts:
- Lithosphere: The land, solid outer layer of the Earth.
- Hydrosphere: The water, total amount of water on the planet in liquid, vapor, and ice forms, including surface water, underground water, and water in the air (e.g., lakes, rivers, oceans, icebergs, aquifers).
- Atmosphere: The layers of gases that surround the planet, held in place by Earth's gravity.

Levels of Organization (Smallest to Largest):
- Organism
- Population
- Species
- Community
- Ecosystem
- Biome
- Biosphere
Individual: An organism and its interactions with its biotic and abiotic environment.
Population: A group of individuals of the same species.
Community: More than one population living in a defined area.
Ecosystem: All organisms (community) in an area and the environment, including biotic and abiotic components.

All organisms need energy to live.
First Law of Thermodynamics: Energy cannot be created or destroyed.
Source of Energy: The sun.
Energy Distribution:
- Not all of the sun’s energy reaches the Earth’s surface.
- 30% is reflected by clouds, dust particles, and water/land surfaces.

Definition: The amount of energy reflected by clouds, water, and land.
Characteristics:
- Light surfaces = High albedo.
- Dark surfaces = Low albedo.

Energy cannot be created or destroyed but can be converted into different forms.
Radiant Energy: From the sun is converted into usable energy by living things.
Energy Transformation #1: Photosynthesis

Producers (plants, algae, some bacteria) convert radiant energy into chemical energy.
Chemical energy is stored in carbohydrate molecules (glucose).
Producers are also referred to as autotrophs because they create their own food.
Formula: $6CO2 + 6H2O \xrightarrow{\text{light energy}} C6H{12}O6 + 6O2$
- Carbon dioxide + Water -> Glucose + Oxygen

Microorganisms near deep-sea vents use hydrogen sulfide ( $H_2S$ ) to produce carbohydrate-based energy in the absence of light.
Formula: $CO2 + 4H2S + O2 \rightarrow CH2O + 4S + 3H_2O$
- This process produces sulfur instead of oxygen.

Energy Transformation #2
Consumers obtain energy by eating producers or other consumers.
Process: Consumers convert chemical energy (glucose) into ATP (main fuel source).
ATP is