Ecosystems and Energy Chapter 3
Dec 23, 2015
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)
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
Levels of Ecology
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
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 ConsumersHerbivores (omnivores)
Secondary ConsumersCarnivores (omnivores)
Tertiary Consumers Detritus Feeders
Decomposers/Saprotrophs
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