Ecosystems Chapter 54

I. Energy Flow Trophic Structures Energy Budget Secondary Productivity Global EB GPP & NPP Biomass Limits of PP- aquatic, terrestrial Secondary Productivity Energy Efficiency Pyramids-production, #s, biomass Biological Magnification

II. Biogeochemical Cycles Water Carbon Nitrogen Phosphorous

III. Human Impact Chemical Cycles Acid precipitation Toxins & biological Magnification Climate change-CO2 & O3

A. Trophic Structures- Energy Flow Energy flow one way- sun is inflow Food chains & webs are short b/c trophic energy level loses 90%

Energy Transfer Energy in Energy moves through from the Sun captured by autotrophs = producers Energy moves through food chain transfer of energy from autotrophs to heterotrophs (herbivores to carnivores) heterotrophs = consumers

Energy Transfer Primary producers primary consumers secondary consumers tertiary consumers Detrivores/Decomposers get energy from detritus most important part in an ecosystem connects all levels

B. Energy Budget Primary Production Producers determine the energy budget for an ecosystem GPP amount of solar energy converted into chemical energy all photsynthesis NPP = GPP- Respiration (cost of staying alive) PP  J/m2/y or biomass

Primary Production Aquatic Systems light & nutrients are limiting factors for PP Terrestrial Systems  temperature, moisture, nutrients

C. Secondary Production The mount of chemical energy in consumers’ food that is converted into their

Energy Inefficiency incomplete digestion metabolism

Pyramids of Production represent the loss of energy from a food chain how much energy is turned into biomass

Pyramid of Numbers levels in pyramids of production are proportional to number of individuals present in each trophic level

Implications Dynamics of energy through ecosystems have important implications for human populations what food would be more ecologically sound? We consume more than just food: water, energy, space/habitat

D. Biological Magnification Toxins can become concentrated in successive trophic levels of food webs Humans produce many toxic chemicals that are dumped into ecosystems. These substances are ingested and metabolized by the organisms in the ecosystems and can accumulate in the fatty tissues of animals. These toxins become more concentrated in successive trophic levels of a food web, a process called biological magnification.

The pesticide DDT, before it was banned, showed this affect. Fig. 54.24 The pesticide DDT, before it was banned, showed this affect. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 54.25 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Biogeochemical Cycles Nutrient cycles Gases cycle on a global level Solids cycle slowly and locally

Fig. 54.15 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

The water cycle is more of a physical process than a chemical one. Fig. 54.16 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

The carbon cycle fits the generalized scheme of biogeochemical cycles better than water. Fig. 54.17 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

The Nitrogen Cycle Nitrogen enters ecosystems through two natural pathways. Atmospheric deposition, where usable nitrogen is added to the soil by rain or dust. Nitrogen fixation, where certain prokaryotes convert N2 to minerals that can be used to synthesize nitrogenous organic compounds like amino acids.

Fig. 54.18 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 54.19 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

III. Human Impact Rising atmospheric CO2. Since the Industrial Revolution, the concentration of CO2 in the atmosphere has increased greatly as a result of burning fossil fuels.

Measurements in 1958 read 316 ppm and increased to 370 ppm today Fig. 54.26 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

The Greenhouse Effect Rising levels of atmospheric CO2 may have an impact on Earth’s heat budget. When light energy hits the Earth, much of it is reflected off the surface. CO2 causes the Earth to retain some of the energy that would ordinarily escape the atmosphere. This phenomenon is called the greenhouse effect. The Earth needs this heat, but too much could be disastrous.

Global Warming Scientists continue to construct models to predict how increasing levels of CO2 in the atmosphere will affect Earth. Several studies predict a doubling of CO2 in the atmosphere will cause a 2º C increase in the average temperature of Earth. Rising temperatures could cause polar ice cap melting, which could flood coastal areas. It is important that humans attempt to stabilize their use of fossil fuels.

Ozone Depletion Life on earth is protected from the damaging affects of ultraviolet radiation (UV) by a layer of O3, or ozone. Studies suggest that the ozone layer has been gradually “thinning” since 1975.

Fig. 54.27b Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Ozone Depletion Probably results from the accumulation of chlorofluorocarbons, chemicals used in refrigeration and aerosol cans, and in certain manufacturing processes. The result of a reduction in the ozone layer may be increased levels of UV radiation that reach the surface of the Earth. This radiation has been linked to skin cancer and cataracts.

The impact of human activity on the ozone layer is one more example of how much we are able to disrupt ecosystems and the entire biosphere.