10-Ecosystems Ecology 1

Ecosystem Ecology

• Big, fierce animals are rare due to multiple factors
• Ecosystems involve interactions between organisms and their surroundings
• Ecosystems range in size, from ponds to deserts
• Ecosystems contain both living (biotic) and non-living (abiotic) components

Ecology in the News

• The average American uses 100-176 gallons of water per day at home
• The average African family uses about 5 gallons per day
• Yearly, 500,000,000 straws are used in the US
• It takes 200 years to break down straws into tiny particles
• Little plastic is recycled and much ends up in the ocean

Need to Know

• Define an ecosystem and understand how materials and energy flow through it.
• Differentiate gross and net primary production and the concept of production efficiency.
• Understand and describe trophic efficiency (Lindeman's efficiency).
• Describe the nitrogen and water cycles.
• Describe how nitrogen pollution and industrial fertilizers impact ecosystems.

Ecosystems

• An ecosystem is a collection of organisms and their environment where they live
• Interactions happen between the organisms and the environment
• Ecosystems include deserts, ponds etc
• Ecosystems encompass biota and the physical environment

Ecosystem Ecology Focus

• Focuses on the flow of energy and materials within ecosystems
• Energy flows through producers (plants), consumers (herbivores, carnivores), and decomposers (bacteria, fungi)
• Abiotic components (carbon dioxide, oxygen, minerals) are essential for cycling
• The cycles are interconnected and crucial for maintaining ecosystem health.

Three Important Concepts

• Abiotic factors (e.g., carbon dioxide, oxygen, nitrogen, minerals)
• Decomposers (e.g., bacteria, fungi)
• Producers (e.g., plants)
• Consumers (e.g., herbivores, carnivores)
• Energy moves from one component to another in a food web
• Materials are cycled through the components

Materials Cycle

• The materials cycle involves the constant exchange and recycling of elements like N, C, and phosphorus
• Decomposers break down organic matter and release inorganic nutrients back into the system
• Energy flows from producers through consumers and decomposers
• Energy is not recycled
• The cycle is interconnected to all parts of the ecosystem

Decomposers

• Decomposers (bacteria and fungi) connect primary producers to consumers
• They convert organic matter into inorganic forms for primary producers to reuse
• Critical for closing material cycles

Learning Catalytics (Question 1)

• Matter is recycled, but energy is not.
• Matter is constantly recycled to be used by producers
• Energy is transferred or transformed, but not recycled

Thermodynamics - 1st Law

• Energy is neither created nor destroyed, only transferred or transformed
• Energy is stored, reflected and / or dissipated as heat

Thermodynamics - 2nd Law

• During energy transformation some energy is rendered unusable
• Energy transfer is not perfectly efficient - some energy is lost as heat

Primary Production

• Photosynthesis converts carbon dioxide and water to glucose, releasing oxygen
• Gross primary production (GPP) is the total amount of light energy plants convert
• Net primary production (NPP) is the amount of energy consumed by the plants for growth, maintenance, and respiration
• GPP is a rate
• Chemical energy is used by plants for growth, reproduction, respiration, and maintenance

Where is Chemical Energy Stored?

• Chemical energy is stored as glucose in the plants.

GPP = NPP + Respiration (plant)

• GPP equals NPP plus plant respiration

NPP

• Represents net primary production, which is the rate of new plant biomass increase
• In many ecosystems, NPP is around 50% of GPP

Which ecosystem has higher NPP?

• Tropical forests typically have higher NPP than the Serengeti plains

NPP is Not Standing Crop

• NPP is the creation of new biomass over time

Best Experiment to Calculate NPP

• Putting wire cages around areas of grass, cutting the grass to the ground, and measuring the amount of new grass growth over a period is the best way to calculate NPP

NPP Estimated from Satellites

• Terrestrial systems contribute 52% of the global NPP
• Aquatic systems contribute 48% of the global NPP

Energy Transfer

• Processes involved in transferring energy from one trophic level to the next involve digestion, metabolism, respiration and growth

Ectotherm and Endotherm Production Efficiency

• Ectotherms have production efficiencies of 10-50 percent
• Endotherms have production efficiencies around 1-5 percent.
• Ectotherms use 65-80% of total energy intake for maintenance
• Endotherms use 85-95% of total energy intake for maintenance

Lindeman's Trophic Efficiency

• Lindeman's efficiency is the percentage of production transferred from one trophic level to another
• Typically around 10%

Trophic Structure and Biomass Pyramids

• Biomass pyramids show relative amounts of biomass at each trophic level
  • In terrestrial systems, producers have the most biomass.
  • In aquatic systems, producers can sometimes have lower biomass than consumers.
  • Pyramids can be inverted if the rates of production of lower trophic levels are high

Element Cycling (Overview)

• Nutrient cycles are called biogeochemical cycles
• Highly mobile elements (carbon, oxygen, nitrogen) cycle globally in the atmosphere
• Less mobile elements (phosphorus) cycle locally

The Four Main Element Cycles

• Carbon (C)
• Water (H₂O)
• Nitrogen (N)
• Phosphorus (P)

The Nitrogen Cycle

• Nitrogen is essential to life and is a key component of proteins and nucleic acids.
• Most nitrogen is found in the atmosphere as N2
• Nitrogen-fixing bacteria convert atmospheric nitrogen to ammonia, which plants use

The Haber-Bosch Process

• The Haber-Bosch process is a method to artificially fix nitrogen

The Water Cycle

• Water is essential for all life
• Water limits productivity and decomposition

Bad Things (Water Issues)

• 1.2 billion people lack clean water
• 18,000 people die each day due to preventable waterborne diseases
• Fossil water is being drained at an unsustainable rate
• Cities, like Beijing and some areas in Mexico city, are sinking due to water overuse

Water Use in Agriculture (California)

• Producing 1 pound of food requires varying amounts of water
• Lettuce requires 23 gallons
• Beef requires 5,214 gallons per pound.