Ecosystems

Ecosystems

An ecosystem is all of the organisms in an area, along with their nonliving environmentExample: aquarium

Trophic Levels

Organisms in a community are related to each other through feeding relationships

Each step up in the transfer of energy is known as a trophic level

All energy ultimately comes from the SUN

Primary Productivity

Primary Productivity:The amount of light energy converted to

sugars by autotrophs in an ecosystemGross vs. Net Primary Productivity

• GPP: the amount of light energy that is converted to chemical energy by photosynthesis per unit time

• NPP: GPP minus the energy used by the primary producers for cellular respiration

Limiting Nutrients

What limits primary production?Aquatic Ecosystems

• Light (depth penetration)• Nitrogen• Phosphorus

Terrestrial Ecosystems• Temperature• Moisture• Minerals

Trophic Levels Producers

Convert solar (or chemical) energy into organic compounds

Primary consumers Eat producers

Secondary consumers Eat primary consumers

Tertiary consumers Eat secondary consumers

Trophic Levels

Decomposers/ Detritivores Eat detritus

(organic waste/remains of dead organisms)

Trophic Levels Ten-Percent Law

Energy is lost through each transfer of energy Only about 10% of the energy at one trophic level is

transferred to the next trophic level

Pyramid of Numbers

Human Impact on Ecosystems Increased Eutrophication

of Lakes Eutrophication – when

lakes shift from having phytoplankton communities dominated by diatoms or green algae to having phytoplankton communities dominated by cyanobacteria

• Leads to the eventual loss of fish

• Accelerated by sewage/factory wastes, leaching of fertilizers into freshwater

Human Impact on Ecosystems Combustion of

Fossil Fuels Leads to acid

precipitation Changes the pH of

aquatic ecosystems and affects the soil chemistry of terrestrial ecosystems

Human Impact on Ecosystems Biological

Magnification Toxins become

more concentrated as they move up the food chain

The biomass at any given trophic level is produced from a much larger biomass ingested from the level below

Human Impact on Ecosystems

Increasing Carbon Dioxide Concentration in the AtmosphereBurning fossil fuels (wood, coal, oil)

releases CO2

Carbon dioxide and water in the atmosphere retain solar heat, causing the greenhouse effect