Ecosystems and Energy
Ecosystems and Energy
Ecology: All Life is Interconnected
Key Questions
What do I need to know?
Trophic levels and their roles in ecosystems
Major processes of cycling for water and carbon
What do I need to think about?
The necessity of decomposition and biogeochemical processes to sustain life
What do I need to understand?
Ecosystems as “units” of nature with recognizable and quantifiable properties of structure and function
Levels of Organization
Global ecology
Landscape ecology
Ecosystem ecology
Community ecology
Population ecology
Organismal ecology
Ecosystem
Definition: All organisms living in a community along with the abiotic factors they interact with.
Boundaries: Defined by natural boundaries and can vary in scale.
Energy Flow Through Ecosystems
Energy Entry
Enters ecosystems as solar radiation.
Transformed into chemical energy.
Energy dissipates as heat; conversions are inefficient - some energy is always lost.
Continuous input from the sun is required to maintain energy flow.
Energy Transfer in Ecosystems
Energy and nutrients pass up the food chain.
Autotrophs build organic molecules using photosynthesis or chemosynthesis.
Key components of the food chain:
Sun
Heat
Primary producers
Primary consumers
Detritus
Secondary and tertiary consumers
Microorganisms and other detritivores
Heterotrophs depend on biosynthetic molecules made by other organisms.
Role of Detritivores and Decomposers
Connect all trophic levels.
Derive energy and nutrients from nonliving organic matter (dead material).
Serve as food for secondary and tertiary consumers.
Primary Production
Definition: The amount of light energy converted to chemical energy by autotrophs during a given time.
Gross Primary Production (GPP): Total primary production conducted.
Net Primary Production (NPP):
Calculated as: NPP = GPP - ext{energy used by primary producers for cellular respiration}
Represents the energy actually available to consumers.
Secondary Production
Definition: Amount of energy in food that a consumer converts into new biomass.
Net Secondary Production: Energy stored in biomass after accounting for energy lost through respiration.
Production Efficiency: The fraction of consumed food not used for respiration, given by:
ext{Production Efficiency} = rac{ ext{Net Secondary Production}}{ ext{Assimilation of Primary Production}} imes 100 ext{%}
Examples of Production Efficiency
For caterpillars feeding on leaves: ~17% of the leaf’s energy is allocated to net secondary production.
Birds and mammals typically show 1-3% production efficiency due to endothermy.
Insects and microorganisms exhibit >40% production efficiency.
The 10% Rule
Trophic Efficiency: The percentage of production transferred from one trophic level to the next is usually around 10%.
Only about 0.1% of primary production reaches tertiary consumers.
Implications for the number of trophic levels possible within an ecosystem.
Example energy transfers:
Primary producers: 10,000 J
Primary consumers: 1,000 J
Secondary consumers: 100 J
Tertiary consumers: 10 J
Biogeochemical Cycles
Nutrient Cycles: Involve the intersection of biotic and abiotic components.
Gaseous nutrients (carbon, oxygen, sulfur, nitrogen) cycle globally.
Less mobile nutrients (phosphorus, potassium, calcium) cycle locally in terrestrial systems and more broadly when dissolved in aquatic systems.
The Water Cycle
Importance: Water is essential for all organisms.
Most commonly used phase of water is liquid.
Distribution:
Oceans: 97% of the biosphere's water
Glaciers and polar ice caps: 2%
Lakes, rivers, and groundwater: 1%
The Carbon Cycle
Key Processes:
Consumers
Decomposition
Photosynthesis
Cellular respiration
Photosynthesis by phytoplankton and transfer of CO2 in the atmosphere, including impacts from burning fossil fuels and wood.
Climate Change!!
Scientific consensus: >97% of actively publishing scientists agree that climate change is anthropogenic.
Major organizations supporting this consensus include:
NASA
AAAS (American Association for the Advancement of Science)
U.S. National Academy of Sciences
IPCC (Intergovernmental Panel on Climate Change)
The Greenhouse Effect
Description: Solar energy enters the atmosphere but does not escape, leading to warming effects similar to those of a greenhouse.
Key greenhouse gases include:
CO2 from fossil fuel emissions
Methane from livestock (e.g., cow emissions)
CFCs from aerosol sprays
Diagram of the Greenhouse Effect
Atmospheric Mechanics:
Sunlight that hits earth is partially reflected, while some is converted to heat.
Greenhouse gases (CO2 and others) trap heat, maintaining Earth's warmth.
Carbon Dioxide Levels
Measurement of CO2 concentrations in parts per million (ppm) over various years.
Current levels have rapidly increased and reached new highs beyond historical lines from previous years.
Temperature Changes
Trends in global temperature relative to past peaks during the Holocene era and changes through significant geological periods.
Discusses historical sea level changes, including a rise of ~400 ft during certain eras.
Impacts of Climate Change
Major Consequences:
Rising sea levels
Increased incidents of drought
Ocean acidification due to increased CO2
Significant impact on agriculture and food security
Adverse effects on plant and wildlife populations
Human Impacts on Biodiversity
Species Extinction Rates:
Difficult to determine under natural conditions; however, current extinction rates are unusually high due to human activities.
Species Diversity
Definition: The variety of species within an ecosystem or globally.
Current statistics: 12% of birds and 21% of mammals are threatened with extinction.
Notable trends: 29% decline in all bird species in North America over the past 50 years.
Ecosystem Diversity
Human Impact:
More than 50% of wetlands in the USA have been drained and transformed into agricultural land, leading to reduced ecosystem diversity.
Why Should I Care??!!
Medicinal Value:
In the USA, 25% of prescription medications contain compounds derived from plants (e.g. Rosy periwinkle’s alkaloids inhibit cancer).
Genetic Diversity Loss:
Loss of species translates to a loss of unique genes, which has significant implications for human benefit.
Example: Decline in bats correlates with increased Midwestern infant mortality rates linked to loss of natural pest control.
Biodiversity and Ecological Welfare
Ecosystem Services:
Practical benefits of biodiversity to humans include:
Air and water purification
Detoxification and decomposition of waste
Crop pollination and pest control
Soil preservation
Economic Value:
The estimated annual value of ecosystem services is $33 trillion, provided for free.
Threats to Biodiversity
Major Threats:
Habitat loss and alteration
Introduced species
Overharvesting
Global change and pollution
Habitat Loss
Concern:
Human alteration of habitats remains the greatest threat to global biodiversity.
Habitat fragmentation and destruction lead to biodiversity loss.
Introduced Species
Definition: Species moved from their native environments to new regions by humans.
Characteristics:
Can spread rapidly without natural predators and disrupt local communities (e.g., Brown Tree Snake).
Often introduced with good intentions leading to disastrous ecological outcomes (e.g., Kudzu).
Overharvesting
Definition: Harvesting natural populations at rates too high for recovery.
Notable Examples:
Elephant populations declining drastically due to ivory poaching.
The last Northern White Rhino died in 2018, showing the extent of human impact on species.
Modern Fishing Impact
Statistics:
Approximately 45% of harvested fish species are overexploited.
Notable decline: 80% decrease in the North Atlantic Bluefin tuna populations within 10 years, valued highly in Japan.
Fishing Techniques
Description of Longline Fishing:
Involves up to 5 million baited hooks over extensive lengths of ocean line, causing bycatch and imperiling many marine species, including critically endangered turtles.