General Biology: Foundations, Energy Flow, and Ecosystem Dynamics

Course Structure and Study Strategies

Preparation and Course Logistics

• Weekly Canvas Page: Check for topics, readings, and lecture materials before each class.

• Time Management: Allocate 15–20 minutes before each lecture for video content, assigned readings, and short quizzes.

• Lecture Materials: Bring any confusing material or questions to class for clarification.

• Problem Sets: Posted on Fridays and due by Monday at 3:00 pm.

• Textbook: Considered less important than other resources.

• Assessment Policy: Lowest exam and three lowest quiz scores may be dropped.

• Office Hours: Available Monday, Wednesday, and Friday (10:30–11:30), Tuesday (11–12).

Core Concepts in Biology

Emergent Properties

Emergent properties are characteristics that arise from the interaction of simpler elements within a system.

• Definition: Traits or behaviors that emerge from the organization and interaction of simpler components.

• Example: The ability of a cell to maintain homeostasis emerges from the coordinated function of its organelles.

Evolution and Unity of Life

Evolution explains the diversity and unity of life through natural selection and shared ancestry.

• Evolution: The process by which species change over time, primarily through natural selection.

• Evidence: Diversity of life forms and shared traits among species point to common ancestry.

• Unity: All living organisms share fundamental traits, such as genetic code and cellular structure.

Biology and Health

• Application: Biological principles are foundational to understanding health and disease.

Energy Flow in Ecosystems

Gross Primary Production (GPP) and Net Primary Production (NPP)

Energy enters ecosystems primarily through photosynthesis and is partitioned into different forms as it moves through trophic levels.

• GPP (Gross Primary Production): Total amount of chemical energy produced by autotrophs (e.g., plants) via photosynthesis.

• NPP (Net Primary Production): The energy remaining after accounting for energy used in cellular respiration by producers.

Key Equation:

$NPP = GPP - R$

Where $R$ is the energy used in cellular respiration or energy lost as heat.

• Only a small percentage of sunlight is stored as chemical energy in organic material.

Assimilated Energy (AE) and Net Production Efficiency (NPE)

• AE (Assimilated Energy): Portion of energy consumed that is used for cellular respiration and new biomass.

• NPP: Represents the energy available for growth and reproduction, can be expressed as biomass or energy.

• NPE (Net Production Efficiency): The ratio of net production (energy stored as new biomass) to assimilated energy.

Key Equation:

$NPE = \frac{NP}{AE}$

• The remaining percentage of assimilated energy is used for cellular respiration.

Trophic Efficiency (TE)

• TE: Efficiency of energy transfer across trophic levels, not just net production at a single level.

• Energy transfer between trophic levels is typically low (often around 10%).

Energy Flow and Chemical Cycling

• Two Key Features of Ecosystems:

  • Continuous energy flow (with energy lost as heat at each transfer).

  • Chemical recycling (elements like carbon and nitrogen are reused).

• Trophic Levels:

  • Grazing food chain: Primary producers → Primary consumers → Higher-level consumers.

  • Detritus food chain: Decomposers feed on non-living organic matter.

• Decomposers: Essential for recycling nutrients; their activity increases with temperature, moisture, and oxygen availability.

Fundamental Requirements for Life

Characteristics of Living Organisms

• Composed of cells

• Cells replicate

• Pass on genetic information

• Respond to environmental changes

• Acquire and use energy

Energy Flow and the Sun

• Primary Source: The sun is the main source of energy for most ecosystems.

• Energy Transfer: Energy is not created or destroyed, but transferred and transformed (First Law of Thermodynamics).

• Second Law of Thermodynamics: Every energy transfer increases entropy; some energy is lost as heat.

• Energy Flow: Energy moves in a linear, one-way direction through ecosystems; it is not a cycle.

Diagram: Energy Flow in Ecosystems

Described Diagram: The sun provides energy to primary producers (plants), which is then transferred to primary consumers (animals). At each step, some energy is lost as heat. Energy flows in one direction, not in a cycle.

Summary Table: Key Energy Terms

Term	Definition	Equation
GPP	Total chemical energy produced by autotrophs	—
NPP	Energy available for growth and reproduction	$NPP = GPP - R$
AE	Assimilated energy used for respiration and new biomass	—
NPE	Net production efficiency	$NPE = \frac{NP}{AE}$
TE	Trophic efficiency (energy transfer between levels)	—

Additional info:

• Some context and definitions have been expanded for clarity and completeness.

• Equations and table structure are inferred from standard biology curriculum.