Ecosystem Dynamics and Resilience

• EE.MS-LS1-3 Ecosystem Dynamics, Functioning, and Resilience
• This standard focuses on the complex interactions within ecosystems and the factors that influence their stability and resilience

Core Idea

• Ecosystems are dynamic and complex webs of interactions between organisms and their environment
• These interactions determine the flow of energy and cycling of matter, which are fundamental to ecosystem functioning
• Ecosystems exhibit resilience, the ability to recover from disturbances and maintain their essential functions

Energy Flow

• Energy enters ecosystems primarily through photosynthesis, performed by producers like plants and algae
• Producers convert light energy into chemical energy in the form of organic molecules such as sugars
• Energy flows through the ecosystem as organisms consume one another, transferring the chemical energy stored in organic matter
• At each trophic level, a significant portion of energy is lost, mainly as heat due to metabolic processes
• This energy loss limits the number of trophic levels in an ecosystem, typically resulting in food chains or food webs with a few levels
• Food webs illustrate the complex feeding relationships among organisms in an ecosystem, showing how energy and matter are transferred through multiple pathways
• Decomposers, such as bacteria and fungi, break down dead organisms and organic waste, releasing nutrients back into the environment and playing a vital role in nutrient cycling

Cycling of Matter

• Matter, in the form of nutrients like carbon, nitrogen, phosphorus, and water, cycles within and among ecosystems
• These cycles involve biological, geological, and chemical processes that move matter through different reservoirs and forms
• The carbon cycle involves the movement of carbon between the atmosphere, land, oceans, and living organisms through photosynthesis, respiration, decomposition, and combustion
• The nitrogen cycle involves the conversion of nitrogen gas in the atmosphere into usable forms by bacteria, followed by uptake by plants, consumption by animals, and decomposition back into the environment
• The phosphorus cycle involves the slow release of phosphorus from rocks through weathering, uptake by plants, and cycling through food webs
• The water cycle involves the continuous movement of water between the atmosphere, land, and oceans through evaporation, transpiration, condensation, precipitation, and runoff

Ecosystem Interactions

• Organisms within an ecosystem interact in various ways, including competition, predation, mutualism, commensalism, and parasitism
• Competition occurs when organisms require the same limited resources, such as food, water, or space, leading to a struggle for survival
• Predation involves one organism (the predator) consuming another organism (the prey), regulating prey populations and influencing community structure
• Mutualism is a relationship where both organisms benefit, such as pollination, where insects transfer pollen between flowers while receiving nectar
• Commensalism is a relationship where one organism benefits, and the other is unaffected, such as epiphytes growing on trees without harming them
• Parasitism is a relationship where one organism (the parasite) benefits, and the other (the host) is harmed, such as ticks feeding on mammals
• These interactions shape the structure and dynamics of ecosystems

Ecosystem Stability

• Ecosystems maintain stability through negative feedback loops, which counteract disturbances and help to restore equilibrium
• For example, an increase in prey population may lead to an increase in predator population, which in turn reduces the prey population, stabilizing both populations
• High biodiversity contributes to ecosystem stability by providing a variety of species that can perform similar functions, increasing resilience to disturbances
• Keystone species play a critical role in maintaining ecosystem structure and function; their removal can have cascading effects throughout the ecosystem
• Ecosystems exhibit resilience, the ability to resist damage or recover quickly from disturbances such as natural disasters, climate change, or human activities
• The rate and extent of recovery depend on the type and intensity of the disturbance, as well as the inherent resilience of the ecosystem

Human Impacts

• Human activities can have significant impacts on ecosystem dynamics and resilience, often leading to ecosystem degradation
• Deforestation removes habitats, reduces biodiversity, and disrupts nutrient cycles, impacting ecosystem functioning
• Pollution from industrial and agricultural sources contaminates air, water, and soil, harming organisms and disrupting ecological processes
• Overexploitation of resources, such as overfishing or overhunting, can deplete populations and destabilize food webs
• Climate change, driven by greenhouse gas emissions, alters temperature and precipitation patterns, affecting species distributions and ecosystem processes
• Invasive species, introduced intentionally or unintentionally by humans, can outcompete native species and disrupt ecosystem dynamics
• Protecting and restoring ecosystems is essential for maintaining biodiversity, ecosystem services, and human well-being

Factors Affecting Ecosystems

• Changes in environmental conditions
  • Climate change
  • Natural disasters
  • Human activities
• Climate change related factors include increased temperatures, altered precipitation patterns, and more frequent extreme weather events, which can shift species distributions
• Natural disasters, such as wildfires, floods, hurricanes, and volcanic eruptions, can cause widespread destruction and alter ecosystem structure and function
• Human activities, such as deforestation, pollution, and urbanization, can degrade habitats and disrupt ecological processes
• Availability of resources
  • Sunlight
  • Water
  • Nutrients
• Sunlight is essential for photosynthesis and energy production in ecosystems
• Water is vital for all life processes and can limit plant growth in arid ecosystems
• Nutrients, such as nitrogen and phosphorus, are required for plant growth and can influence primary productivity
• Interactions between species
  • Competition
  • Predation
  • Symbiosis
• These interactions shape the structure and dynamics of ecosystems
• Invasive species
  • Outcompete native species
  • Alter ecosystem structure
  • Reduce biodiversity
• Invasive species can disrupt food webs, alter nutrient cycles, and introduce diseases, leading to significant ecological and economic impacts

Indicators of Ecosystem Health

• Biodiversity
  • Number and variety of species
  • Genetic diversity within species
• Nutrient cycling
  • Rates of decomposition
  • Nutrient uptake
• Primary productivity
  • Rate of photosynthesis
  • Biomass production
• Water quality
  • Levels of pollution
  • Nutrient content
• Soil health
  • Organic matter content
  • Structure
• Monitoring these indicators over time can provide insights into the health and stability of ecosystems

Investigating Ecosystem Dynamics

• Design investigations to gather evidence
  • Effect of specific factors or conditions
  • Impact of ecological changes
• Collect evidence
  • Analyzing and interpreting data
  • Providing explanations of ecosystem health
• Examples
  • Measuring plant growth
  • Comparing species diversity
  • Monitoring water quality
• Ecosystems can be modeled to determine the effect of a change or disruption
  • Example: modeling the effect of a change in predator population on the rest of the food web
• Ecosystem models can be used to explore the impact of climate change, pollution, and other disturbances on ecosystems
• The complexity and interconnections within an ecosystem can make it difficult to predict the outcome precisely