Ecology: Nutrient Cycles & Population Dynamics David Mellor, PhD Citizen Science Coordinator Virginia Master Naturalists Overview of Ecology Definition and Scope Energy and Food Webs Nutrient Cycles Population Dynamics Ecological Interactions Community Structure Ecosystem Services Human Impacts Nutrient Cycles The movement of nutrients through different environments on Earth Nutrients: Carbon Nitrogen Water Phosphorous Sulfur Nutrient Cycles Nutrients move between different reservoirs. Examples of nutrient reservoirs: Mineral deposits Atmosphere Terrestrial ecosystems Marine environments Nutrient Cycles Reservoirs can be classified as: Accessible or inaccessible to living things Organic or inorganic materials 1)Accessible Organic 2)Accessible Inorganic 3)Inaccessible Organic 4)Inaccessible Inorganic Nutrients move between reservoirs through many different processes: Photosynthesis(moves carbon into plants) Respiration (moves carbon out of living organisms) Weathering (moves nutrients out of rocks) Volcanism (moves carbon out of the Earth) Decomposition(moves nutrients out of dead organisms) Excretion (moves nutrients out of living organisms) Nutrient Cycles Nutrients move between reservoirs through many different processes: Photosynthesis(moves carbon into plants) Respiration (moves carbon out of living organisms) Weathering (moves nutrients out of rocks) Volcanism (moves carbon out of the Earth) Decomposition(moves nutrients out of dead organisms) Excretion (moves nutrients out of living organisms) Nutrient Cycles Nutrients move between reservoirs through many different processes: Photosynthesis(moves carbon into plants) Respiration (moves carbon out of living organisms) Weathering (moves nutrients out of rocks) Volcanism (moves carbon out of the Earth) Decomposition(moves nutrients out of dead organisms) Excretion (moves nutrients out of living organisms) Nutrient Cycles Nutrients move between reservoirs through many different processes: Photosynthesis(moves carbon into plants) Respiration (moves carbon out of living organisms) Weathering (moves nutrients out of rocks) Volcanism (moves carbon out of the Earth) Decomposition(moves nutrients out of dead organisms) Excretion (moves nutrients out of living organisms) Nutrient Cycles Nutrients move between reservoirs through many different processes: Photosynthesis(moves carbon into plants) Respiration (moves carbon out of living organisms) Weathering (moves nutrients out of rocks) Volcanism (moves carbon out of the Earth) Decomposition(moves nutrients out of dead organisms) Excretion (moves nutrients out of living organisms) Nutrient Cycles Nutrients move between reservoirs through many different processes: Photosynthesis(moves carbon into plants) Respiration (moves carbon out of living organisms) Weathering (moves nutrients out of rocks) Volcanism (moves carbon out of the Earth) Decomposition(moves nutrients out of dead organisms) Excretion (moves nutrients out of living organisms) Nutrient Cycles Nutrients move between reservoirs through many different processes: Photosynthesis(moves carbon into plants) Respiration (moves carbon out of living organisms) Weathering (moves nutrients out of rocks) Volcanism (moves carbon out of the Earth) Decomposition(moves nutrients out of dead organisms) Excretion (moves nutrients out of living organisms) Nutrient Cycles Nutrients move between reservoirs through many different processes: Photosynthesis(moves carbon into plants) Respiration (moves carbon out of living organisms) Weathering (moves nutrients out of rocks) Volcanism (moves carbon out of the Earth) Decomposition(moves nutrients out of dead organisms) Excretion (moves nutrients out of living organisms) Nutrient Cycles Carbon Cycle Inorganic, Available Atmosphere Soil Water Organic, Available Living organisms Detritus Organic, Unavailable Oil and Gas Inorganic, Unavailable Rocks and minerals Photosynthesis Assimilation Respiration, Decomposition Burning fossil fuels, volcanism Rock formation Weathering Fossilization Carbon Cycle Earths Interior 75,000,000 Gigatons (oil, gas, peat, limestone) Oceans 38,000 Gigatons (Calcium carbonate shells, carbonic acid) Terrestrial Biosphere 550 Gigatons (living organisms) Atmosphere 720 Gigatons (CO2 and Methane) Sedimentation Volcanoes, Combustion Photosynthesis Respiration Dissolve Detritus N2N2 N2N2 Atmospheric Nitrogen (N 2 ) Ammonification (NH 4 + ) Nitrification (NO 2 - ) Nitrogen Fixing Bacteria in Soil or Root Nodules Denitrifying Bacteria Assimilation of Nitrates (NO 3 - ) Decomposers Nitrogen Cycle Water Cycle Questions Describe ways in which natural nutrient cycles are being disrupted by human activities. What are the consequences of disrupting natural nutrient cycles? Population Dynamics Limiting Factors Growth Rates Carrying Capacity Reproductive Strategies Limiting Factors Environmental Factor Response of Organism Environmental Factor Response of Organism OptimumSaturation Limiting Factors, Examples Food availability Number of possible burrows Distance from predators Growth rate Temperature Altitude pH Rainfall Population Density OptimumSaturation Limiting Factors Questions Describe some more environmental factors that could affect an organism. Describe at least three more measurable responses of an organism. Growth Rates dN (Ndt) = r = b - d The change in the number of organisms over time per organism equals the rate of growth of the population (r), which equals the number of births (b) minus deaths (d). Carrying Capacity & Growth Curves Time Population Size Stabilized population from S-shaped growth curve Carrying Capacity Exponential growth leads to population crash if carrying capacity is overshot too quickly Reproductive Strategies r Strategy Short maturation time Short lifespan Many offspring per reproductive event Usually one reproductive event per lifetime No parental care K Strategy Long maturation time Long lifespan Few offspring per reproductive event Usually many reproductive events per lifetime Extensive parental care K Strategy R Strategy In Between Population Dynamics Questions Why might different reproductive strategies be favored in different environmental conditions? Think about environments that have lots of change or disturbance occurring versus more stable environments.