Ecosystems Chapter 30

Ecosystem An array of organisms and their physical environment, interconnected through a one-way flow of energy and cycling of raw materials

Modes of Nutrition Photoautotrophs Heterotrophs Capture sunlight or chemical energy Primary producers Heterotrophs Extract energy from other organisms or organic wastes Consumers, decomposers, detritivores

Simple Ecosystem Model Energy input from sun Producers Autotrophs (plants and other self-feeding organisms) Nutrient Cycling Consumers Heterotrophs (animals, most fungi, many protists, many bacteria) Energy output (mainly metabolic heat)

Simple Ecosystem Model The role of organisms in an ecosystem

(fourth-level consumer) (third-level consumer) (second-level consumer) fifth trophic level top carnivore (fourth-level consumer) marsh hawk fourth trophic level carnivore (third-level consumer) crow third trophic level carnivore (second-level consumer) garter snake second trophic level herbivore (primary consumer) cutworm first trophic level autotroph (primary producer) flowering plants Fig. 30-3, p.528

Tall-Grass Prairie Food Web marsh hawk sandpiper crow snake frog weasel badger coyote spider sparrow pocket gopher ground squirrel vole earthworms, insects grasses, composites

tallgrass prairie food web marsh hawk Connections in a tallgrass prairie food web Higher Trophic Levels crow upland sandpiper garter snake frog weasel badger coyote spider Second Trophic Level sparrow earthworms, insects prairie vole pocket gopher ground squirrel First Trophic Level grasses, composites Fig. 30-4, p.529

Which statement about ecosystems is false? energy flows in a cycle between producers and consumers nutrients are recycled by passing from producers to consumers and back again via decomposers in most ecosystems, energy flow begins with the capture of solar energy by photosynthesizers heterotrophs include bacteria and fungi

Rain Forest Rain-forest food web

Energy Losses Energy transfers are never 100% efficient Some energy is lost at each step Limits number of trophic levels in an ecosystem

Two Types of Food Webs Grazing Food Web Detrital Food Web Energy Input: Energy Input: Transfers: Transfers: Producers (photosynthesizers) Producers (photosynthesizers) energy losses as metabolic heat and as net export from ecosystem energy in organic wastes, remains energy losses as metabolic heat and as net export from ecosystem energy in organic wastes, remains herbivores decomposers decomposers carnivores detritivores detritivores decomposers Energy Output Energy Output

Ecological Pyramids Primary producers are bases for successive tiers of consumers Biomass pyramid Dry weight of all organisms Energy pyramid Usable energy decreases as it is transferred through ecosystem

Biomass Pyramid Aquatic ecosystem, Silver Springs, Florida Long-term study of a grazing food web third-level carnivores (gar, large-mouth bass) 1.5 second-level consumers (fishes, invertebrates) decomposers, detritivores (bacteria, crayfish) 1.1 first-level consumers (herbivorous fishes, turtles, invertebrates) 37 primary producers (algae, eelgrass, rooted plants) 809 5

Energy Pyramid Primary producers trapped about 1.2% of the solar energy that entered the ecosystem 6–16% passed on to next level top carnivores 21 decomposers + detritivores = 5,080 carnivores 383 herbivores 3,368 producers 20,810 kilocalories/square meter/year

Energy flow at Silver Springs Silver Springs Study Energy flow at Silver Springs

Biogeochemical Cycle Flow of an essential substance from the environment to living organisms and back to the environment Main reservoir is in the environment Geologic processes, decomposers aid cycles

Three Categories Hydrologic cycle Atmospheric cycles Water Atmospheric cycles Nitrogen and carbon Sedimentary cycles Phosphorus and other nutrients

Hydrologic Cycle atmosphere precipitation onto land 111,000 wind-driven water vapor 40,000 evaporation from ocean 425,000 precipitation into ocean 385,000 evaporation from land plants (evapotranspiration) 71,000 surface and groundwater flow 40,000 ocean land

Watershed A region where precipitation is funneled into a single stream or river

Hubbard Brook Experiment A watershed was experimentally stripped of vegetation All surface water draining from watershed was measured Deforestation caused six-fold increase in calcium content of runoff water

Global Water Crisis Limited amount of fresh water Desalinization is expensive and requires large amounts of energy Aquifers are being depleted Groundwater is contaminated Sewage, agricultural runoff, and industrial chemicals pollute rivers

Aquifer Depletion Hawaiian Islands Alaska

water hydrologic hydrodynamic precipitation When the Earth's waters move from ocean to atmosphere to land and back again, it is called the _____ cycle. water hydrologic hydrodynamic precipitation

A watershed is _____. a stream or river a river that discharges water directly into the ocean a region where precipitation becomes funneled into a single stream or river a region where precipitation becomes funneled into a reservoir for use in human communities

Carbon Cycle Carbon moves through atmosphere, food webs, ocean, sediments, and rocks Sediments and rocks are the main reservoir Combustion of fossil fuels changes natural balance

bicarbonate and carbonate in ocean water diffusion between atmosphere and ocean combustion of fossil fuels bicarbonate and carbonate in ocean water photosynthesis aerobic respiration marine food webs death, sedimentation incorporation into sediments uplifting sedimentation marine sediments Carbon Cycle: Marine

combustion of fossil fuels atmosphere volcanic action combustion of fossil fuels photosynthesis aerobic respiration combustion of wood terrestrial rocks deforestation weathering land food webs soil water peat, fossil fuels death, burial, compaction over geologic time leaching, runoff Carbon Cycle: Land

My Carbon Cycle 1. I eat carbohydrate molecules. These are molecules of fuel which I will “burn”. Some of the energy released when I burn them will be trapped for me to use. The rest will be lost as heat. The waste products of burned fuel are carbon dioxide and water. I breathe these out. Plants (or other producers) take in carbon dioxide from the atmosphere and use it to make carbohydrate.

According to the last slide, why do I eat carbohydrates? Because they taste good. Because they contain lots of vitamins. Because they contain lots of energy. Because they are low in calories.

Energy saved from burning up my fuel is saved in the form of : Muscle ATP Fat Heat

The only reason I need to breathe in oxygen is : I need oxygen to “burn” fuel molecules. All living things need oxygen. Oxygen + carbon = carbon dioxide. Oxygen is corrosive.

Breathing out : Helps me regulate my body temperature. Gets rid of excess fuel molecules. Burns extra calories. Gets rid of the waste products of burned fuel.

The carbon in the plants I eat comes from : The atmosphere. The food they eat. The soil. Water.

The carbon in the steak I eat comes from : Supplements in animal feed. Vitamins. The cow’s drinking water. The plants eaten by the cow.

Greenhouse Effect Greenhouse gases impede escape of heat from Earth’s surface

Long-term increase in temperature of Earth’s lower atmosphere Global Warming Long-term increase in temperature of Earth’s lower atmosphere

Carbon Dioxide Increase Carbon dioxide levels fluctuate seasonally Average level is steadily increasing Burning of fossil fuels and deforestation are contributing to the increase

Other Greenhouse Gases CFCs: synthetic gases used in plastics and in refrigeration Methane: released by natural gas production, livestock Nitrous oxide: released by bacteria, fertilizers, and animal wastes

Greenhouse Gases Increasing

Table 30-1, p.537

Nitrogen Cycle Nitrogen is used in amino acids and nucleic acids Main reservoir is nitrogen gas in the atmosphere Nitrogen gas can’t enter food web

Fig. 30-16, p.538

Nitrogen Fixation Plants cannot use nitrogen gas Nitrogen-fixing bacteria convert nitrogen gas into ammonia (NH3) Ammonia and ammonium can be taken up by plants

Air Pollution Effects of nitrogen oxides released by burning fossil fuels