Ecosystems and Energy

Ecosystems and Energy Chapter 3

Ecology • Study of the interactions of organisms and their living and non-living environment • Many different scales to ecology • Abiotic factor – Non-Living environment • Example: Wind, soil, precipitation • Biotic factor – Living environment • Example: all organisms (plants, people)

Levels of Ecology • Organism – any living thing • Species – Group of organisms who interbreed and produce fertile offspring • Population – A group of organisms in the same species that live in the same area at the same time • Community – All populations in the same area, at the same time that interact • Ecosystem – A community together with its physical environment • Landscape – several interacting ecosystems • Biosphere – All living organisms on Earth

Biosphere - All living organisms on Earth • Hydrosphere – All of Earth’s water supply • Atmosphere – Gases that surround the Earth • Lithosphere – Soil and rock of Earth’s crust Ecology encompasses the study of the interrelationships among Earth’s biosphere, hydrosphere, atmosphere and lithosphere

Energy – ability to do work • Energy is the capacity to do work • measured in kJ (work) or kcal (heat) • Kcal = raise 1kg water 1 degree = 4.184 kJ • Different forms of energy • Electrical, chemical, solar, mechanical, nuclear, thermal • Potential vs. Kinetic energy

Thermodynamics • Open system – • Closed system -

First Law of Thermodynamics • Energy cannot be created or destroyed. It can be transferred from one form to another • An organism cannot create the energy that it requires to live • Plants • Sponge • Bacteria • Humans

Second Law of Thermodynamics • Whenever energy is converted from one form to another, some usable energy is lost in thermal energy that disperses into the environment • Entropy – Measure of disorder or randomness • Entropy tends to increase over time • No energy conversion process is 100% efficient • Cars = 20-30% efficient • Cells = 50% efficient • Order is maintained through constant energy input

Photosynthesis • Light energy from the sun is converted to chemical energy carbohydrates (glucose) • Uses photosynthetic pigments (chlorophyll) 6CO2 + 12H2O + sun  C6H12O6 + 6H2O + 6O2

Cellular Respiration • Organic molecules (glucose) are broken down to release energy • Usually in the presence of water and oxygen C6H12O6 + 6O2 + 6H2O  6CO2 + 12H2O + energy

Energy FLOW in an ecosystem • Enters as solar energy (sun) • Photosynthesis (plants) • Stored energy (organic molecules) • Cellular respiration • Some lost to environment (2nd Law of thermodynamics)

Roles in an ecosystem • Producers/Autotrophs • Consumers/Heterotrophs • Primary Consumers • Herbivores (omnivores) • Secondary Consumers • Carnivores (omnivores) • Tertiary Consumers • Detritus Feeders • Decomposers/Saprotrophs

Food chain Always linear Simplistic

Food Web More complex

Ecological Pyramid Shows relative energy values in each trophic level 10% rule

Pyramid of numbers • Usually more producers than consumers • More prey than predators

Pyramid of Biomass • Biomass – Quantitative estimate of total mass of living material • Usually in units (g/m2)

Pyramid of energy • Energy content (kcal/m2/year) • Never 100% efficient • 10% Rule • Usually not more than 4 or 5 trophic levels

Productivity of Producers • Gross Primary Productivity – (GPP) • Energy that is captured during photosynthesis • Net Primary Productivity (NPP) • Energy that remains in a plant after respiration NPP = GPP – Respiration

Productivity • Units : kcal/m2/year • Energy fixed by photosynthesis • Grams of carbon in tissue • Most productive ecosystems: • Rainforests • Wetlands, swamps, marshes • Most unproductive ecosystems: • Tundra, deserts • Open ocean

The NPP for a particular river ecosystem is measured at 8833 kcal/m2/year. Respiration by the aquatic producers is estimated at 11,977 kcal/m2/year. Calculate the GPP for the ecosystem. NPP = GPP – R 8833 = GPP – 11,977 GPP = 8,833 + 11,977 GPP = 20,810 kcal/m2/year

Ecosystems and Energy