Energy Systems

Introduction

Understanding energy systems is crucial in the study of Sports, Exercise, and Health Science (SEHS). Energy flow within ecosystems, food production systems, and the atmospheric energy system all play significant roles in maintaining the balance and sustainability of our environment. This document provides a detailed analysis of these energy systems, breaking down complex ideas into digestible sections.

Energy & Biomass in Ecosystems

Energy Flow in Ecosystems

Energy flows through ecosystems in a one-way stream, from primary producers to various consumers. The primary source of this energy is sunlight, which is captured by producers through photosynthesis.

Photosynthesis

Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose. The simplified equation for photosynthesis is:

$$ 6CO_2 + 6H_2O + light \rightarrow C_6H_{12}O_6 + 6O_2 $$

Respiration

Respiration is the process by which organisms convert glucose and oxygen into energy, carbon dioxide, and water. This process can be summarized by the equation:

$$ C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + energy $$

Trophic Levels & Food Chains

Energy is transferred through trophic levels in a food chain from producers to primary consumers (herbivores), then to secondary consumers (carnivores), and so on. Each step up the chain represents a trophic level.

Food Webs

A food web is a more complex representation of how energy flows through an ecosystem, showing multiple interconnected food chains.

Energy Losses in Food Chains

At each trophic level, energy is lost primarily through metabolic processes as heat. Typically, only about 10% of the energy is transferred from one trophic level to the next.

Productivity & Biomass

• Gross Primary Productivity (GPP): Total amount of energy captured by producers.
• Net Primary Productivity (NPP): Energy remaining after producers' respiration, available to consumers.

Ecological Pyramids

Ecological pyramids visually represent the distribution of biomass, energy, or numbers among trophic levels.

Human Impacts on Energy & Matter Flows

Human activities such as deforestation, agriculture, and urbanization can significantly alter energy and matter flows in ecosystems.

Note

Human activities can disrupt the natural flow of energy and matter, leading to ecological imbalances.

Energy Inputs and Outputs in a Food Production System

Factors Affecting Energy Efficiency

• Climate: Affects crop growth and energy input requirements.
• Soil Type: Influences water retention and nutrient availability.
• Crop Type: Different crops have varying energy efficiencies and nutritional values.

Energy Flow in Ecosystems

Constant Supply of Energy and Matter

Ecosystems require a constant input of energy (usually from the sun) and matter to sustain life.

Energy Conversion by Producers

Producers convert solar energy into chemical energy through photosynthesis, forming the base of the food web.

Transfer of Energy Between Trophic Levels

Energy is transferred from one trophic level to the next, with significant losses at each stage.

Role of Decomposers

Decomposers break down dead organic matter, recycling nutrients back into the ecosystem.

Matter Flow

• Decomposition: Breakdown of organic matter.
• Nutrient Cycling: Movement of nutrients through biotic and abiotic components.
• Precipitation: Part of the water cycle, influencing nutrient availability.

First Law of Thermodynamics

Conservation of Energy

The first law of thermodynamics states that energy cannot be created or destroyed, only transformed. In ecosystems, energy transformations include photosynthesis and respiration.

Energy Transformation Within Ecosystems

Energy is transformed from one form to another, maintaining the balance of energy within the ecosystem.

Tip

Remember that energy transformations are never 100% efficient; some energy is always lost as heat.

Types of Systems

Open Systems

Exchange both energy and matter with their surroundings. Most ecosystems are open systems.

Closed Systems

Exchange energy but not matter with their surroundings.

Isolated Systems

Do not exchange energy or matter with their surroundings. True isolated systems are rare in nature.

Energy and Matter Flow in Different Systems

Understanding the differences between these systems helps in studying how energy and matter flow within and between ecosystems.

Energy Sources Uses & Management

Energy Sources & Sustainability

• Renewable Energy: Solar, wind, hydro, and geothermal.
• Non-Renewable Energy: Fossil fuels such as coal, oil, and natural gas.
• Sustainability: Using energy sources that do not deplete resources or harm the environment.

Pyramid of Productivity

Representation of Energy Stored in Biomass

A pyramid of productivity shows the rate at which energy is stored as biomass in each trophic level over a specific period.

Exothermic & Endothermic Reactions

Enthalpy Changes

• Exothermic Reactions: Release energy (negative enthalpy change).
• Endothermic Reactions: Absorb energy (positive enthalpy change).

Thermodynamically Possible Reactions

Reactions that can occur based on energy changes and entropy.

Kinetic Control of Reactions

Even if a reaction is thermodynamically possible, it may be slow due to kinetic barriers.

Systems Approach in Food Production

Inputs, Processes, and Outputs

• Inputs: Seeds, water, fertilizers, energy.
• Processes: Planting, growing, harvesting.
• Outputs: Crops, waste.

Feedback Effects in Systems

• Positive Feedback: Enhances changes, leading to exponential growth or decline.
• Negative Feedback: Stabilizes the system by counteracting changes.

Example

In agriculture, the use of fertilizers can increase crop yield (positive feedback), but excessive use can lead to soil degradation (negative feedback).

Atmospheric Energy System

Input and Output Energy

• Input: Solar radiation.
• Output: Long-wave radiation emitted by the Earth.

Energy Transfer/Flow

• Convection: Transfer of heat by the movement of fluids.
• Conduction: Transfer of heat through direct contact.
• Radiation: Transfer of energy through electromagnetic waves.

Energy Storage

• Land: Absorbs and releases heat.
• Oceans: Store large amounts of heat.
• Clouds: Reflect and absorb solar radiation.
• Atmosphere: Distributes heat around the Earth.

Global Warming and Diurnal Energy Budget

• Global Warming: Increase in Earth's average temperature due to greenhouse gases.
• Diurnal Energy Budget: Balance of energy input and output over a 24-hour period.

Components of the Daytime Energy Budget

• Solar Radiation: Main source of energy.
• Reflection: Part of solar radiation is reflected back into space.
• Surface Absorption: Energy absorbed by the Earth's surface.
• Sensible Heat Transfer: Heat transfer between the surface and the air.
• Long-Wave Radiation: Energy emitted by the Earth.
• Latent Heat Transfer: Energy used in the evaporation of water.

Common Mistake

It is a common misconception that all energy from the sun is absorbed by the Earth. In reality, a significant portion is reflected back into space.

By understanding these concepts, students can gain a comprehensive view of how energy systems function within ecosystems and the broader environment. This knowledge is essential for making informed decisions about energy use and sustainability.