Life Science Unit 5: Ecosystem Level - Energy in Ecosystems Notes

Life Science Unit 5: Ecosystem Level - Energy in Ecosystems Notes

Introduction

  • Created by: Michael Banino

  • This unit covers the concepts related to energy in ecosystems, focusing on various aspects of productivity, trophic levels, and biodiversity, among others.

Lesson Overview

Lesson Structure

  • Lesson 1: The energy powering life: Primary Productivity and Biomass

  • Lesson 2: Energy transfers across Trophic levels (Part I)

  • Lesson 3: Energy transfers across Trophic levels (Part II) + [POGIL]

  • Lesson 4: Factors Affecting Populations

  • Lesson 5: Carrying Capacity, Competition, and Biodiversity

  • Lesson 6: Biodiversity and Ecosystem Resilience

  • Lesson 7: Formative

  • Lesson 8: Summative

Lesson 1: The Energy Powering Life

Key Concepts

  • Energy powering life originates from the sun as solar energy, which is a limited resource.

  • Productivity is defined as the rate at which energy is stored in organic matter (biomass).

  • Gross productivity indicates the total energy captured, while net productivity signifies the energy stored as biomass after metabolic processes.

  • Some organisms demonstrate greater efficiency in converting energy into biomass than others.

Important Definitions

  • Insolation: Incoming solar radiation.

  • Biomass: The total mass of living material in a designated area (excluding water).

  • Biological productivity: Rate of energy storage in biomass.

  • Producers: Organisms that produce their own food, typically plants.

  • Net primary productivity (NPP): The amount of energy available for growth after respiration by plants.

Ecological Principles

  • Incoming shortwave radiation has two potential outcomes:

    1. Reflect back to space.

    2. Be absorbed and re-emitted as longwave radiation.

  • On Earth, absorbed solar energy can also be captured by primary producers (e.g., plants) through photosynthesis, thereby entering the food chain.

Photosynthesis Process

  • Plants utilize photosynthesis to convert light energy into chemical energy.

  • The chemical energy is stored in biomolecules such as:

    • Glucose

    • Starches

    • Lipids

    • Proteins

Measuring Biomass and Productivity

  • Production is quantified as energy per area (e.g., extkcal/m2ext{kcal/m}^2).

  • Productivity refers to production per unit time, measured differently according to energy or biomass.

  • Gross productivity refers to total energy acquired by producers through photosynthesis, while net productivity relates to energy available for organism growth after respiration.

Mung Bean Experiment

  • Mung beans were grown in class to calculate NPP based on changes in biomass over time.

Energy Transfer in Consumers

  • Consumers derive energy by ingesting biomass.

  • Gross Secondary Productivity (GSP): Total energy acquired by consumers from food.

  • Net Secondary Productivity (NSP): Energy remaining post-respiration for consumer growth.

Practice Problems

  • Problem 1: Given NPP = 8,000 kcal/m²/year and respiration = 12,000 kcal/m²/year, find GPP:

    • NPP=GPP−RNPP = GPP - R

    • 8,000=GPP−12,0008,000 = GPP - 12,000

    • GPP=20,000extkcal/m2/extyrGPP = 20,000 ext{ kcal/m}^2/ ext{yr}

  • Problem 2: Calculation of efficiency using the formula:

    • ext{Efficiency} = rac{ ext{output}}{ ext{input}} imes 100 ext{%}

    • Example calculations for a rabbit (8.9%) and cockroach (40%) based on NSP and GSP.

Lesson 2: Energy Transfers across Trophic Levels

Core Ideas

  • Organisms utilize energy mostly for respiration, with the excess stored as new biomass (net productivity).

  • Trophic levels categorize organisms based on their feeding relationships:

    • 1st level: Primary Producers

    • 2nd level: Primary Consumers

    • 3rd level: Secondary Consumers

    • 4th level: Tertiary Consumers

Vocabulary

  • Trophic levels: Position in the food chain.

  • Trophic pyramid: Model illustrating energy distribution among trophic levels.

  • Herbivore: Primary consumers feeding on plants.

  • Carnivore: Organisms feeding on other animals.

  • Decomposers: Organisms breaking down dead matter.`

Energy Efficiency

  • Energy transfer between trophic levels is not efficient; generally, only around 10% of energy passes to the next level.

  • Energy Pyramid illustrates energy available at each level; a significant amount (90%) is lost as heat or waste.

Food Chain and Food Web Models

  • Food Chain: Simplified linear representation of energy flow.

  • Food Web: Complex network demonstrating multiple feeding interactions within an ecosystem.

Lesson 3: Energy Transfers Across Trophic Levels (Part II)

Key Concepts

  • Finite solar energy limits productivity: Producers require more solar energy to generate biomass at higher trophic levels.

  • Energy lost at levels is converted into heat and released into the atmosphere.

  • Detritivores and decomposers feed on detritus and waste biomass.

Models and Diagrams

  • Use of food chains and webs to depict relationships and energy flow.

  • Discussing limitations of representation regarding detritivores and decomposers' roles.

Lesson 4: Factors Affecting Populations

Central Themes

  • Organisms can be classified at various levels (species, populations, communities, ecosystems).

  • Population growth is influenced by biotic (living) and abiotic (non-living) factors.

Definitions

  • Carrying Capacity: Maximum population size that can be sustained by an ecosystem.

  • Biotic Factors: Include competition, predation, availability of resources, and disease.

  • Abiotic Factors: Include temperature, sunlight, climate, water availability, and pH.

Population Dynamics

  • Discussing density-dependent (e.g., disease, competition) versus density-independent factors (e.g., disasters) affecting growth.

  • Biotic potential: Hypothetical maximum growth rate under optimal conditions versus logistic growth: Actual growth rate considering limited resources.

Lesson 5: Carrying Capacity, Competition, and Biodiversity

Main Ideas

  • Population growth often occurs at the expense of competing species due to limited resources.

  • Understanding different types of biodiversity and their measurements, including species richness and evenness.

Key Vocabulary

  • Biodiversity: Variety of life in a specific area or ecosystem.

  • Environmental Resistance: Factors that limit population growth, creating negative feedback loops.

Human Impact

  • Discussion on how human activities can influence biodiversity and ecosystem capacity.

Lesson 6: Biodiversity and Ecosystem Resilience

Objective

  • Examine the role of biodiversity in reinforcing an ecosystem's ability to adapt to changes or stressors.

Key Concepts

  • Ecosystems with greater biodiversity are typically more resilient to environmental changes and disturbances.

Activities

  • Constructing a food web to simulate how ecosystems respond to stress testing resilience.

Lesson 7: Formative Quiz & Unit 5 Review

Preparation

  • Students are required to study concepts covered throughout Unit 5 to prepare for the upcoming summative assessment.

Lesson 8: Summative Test

Closure

  • Summative assessment to evaluate comprehensive understanding of energy in ecosystems.