Ecosystems

An ecosystem is all of the organisms in an area, along with their nonliving environment Example: aquarium Living + Non-living (Biotic + Abiotic)

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

Trophic Levels

Decomposers/ Detritivores Eat detritus (organic waste/remains of dead organisms) Can fit in to a food chain or web at any location

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

Pyramid of Numbers/Biomass/Ener gy

Numbers, energy, & biomass decreases as one moves up the food chain.

Biomass- dry mass of organic matter

Trophic Levels

Ten-Percent Law Usable energy is lost through each transfer of energy Why? (Remember the law of conservation of energy says energy cannot be created or destroyed; it only changes form.) Only about 10% of the energy at one trophic level is transferred to the next trophic level. 90% is lost as heat with each transfer.

Food Chain

A straight-line sequence of who eats whom Simple food chains are rare in nature marsh hawk upland sandpiper garter snake cutworm plants

Tall-Grass Prairie Food Web

marsh hawk sandpiper crow snake frog weasel badger coyote spider earthworms, insects sparrow vole grasses, composites pocket gopher ground squirrel

Primary Productivity

Primary Productivity: The amount of light energy converted to sugars by autotrophs in an ecosystem Gross 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 GPP-R=NPP

Limiting Nutrients

What limits primary production?

Aquatic Ecosystems Light (depth penetration) Nitrogen Phosphorus Terrestrial Ecosystems Temperature Moisture Minerals (N & P are the main limiting factors for plants.)

Biogeochemical Cycle

The flow of a nutrient from the environment to living organisms and back to the environment Main reservoir for the nutrient is in the environment

Hydrologic Cycle

Atmosphere

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

Ocean Land

Figure 48.14

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

Carbon Cycle - Marine

Figure 48.16

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

Carbon Cycle - Land

Figure 48.16

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Carbon in Atmosphere

Atmospheric carbon is mainly carbon dioxide Carbon dioxide is added to atmosphere Aerobic respiration, volcanic action, burning fossil fuels Removed by photosynthesis

Greenhouse Effect

Greenhouse gases impede the escape of heat from Earth’s surface Figure 48.18, Page 880

Global Warming

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

Figure 48.19, Page 881

Nitrogen Cycle

Nitrogen is used in amino acids and nucleic acids Main reservoir is nitrogen gas in the atmosphere

Nitrogen Cycle

gaseous nitrogen (N 2 ) in atmosphere nitrogen fixation by industry food webs on land fertilizers uptake by autotrophs excretion, death, decomposition uptake by autotrophs nitrogen fixation nitrogenous wastes, remains NO 3 in soil dentrification ammonification 2. Nitrification NH 3 ,NH 4 + in soil leaching 1. Nitrification NO 2 in soil leaching

Figure 48.21

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Nitrogen Fixation

Plants cannot use nitrogen gas Nitrogen-fixing bacteria convert nitrogen gas into ammonia (NH 3 ) Ammonia and ammonium can be taken up by plants

Ammonification & Nitrification

Bacteria and fungi carry out ammonification conversion of nitrogenous wastes to ammonia Nitrifying bacteria convert ammonium to nitrites and nitrates

Nitrogen Loss

Nitrogen is often a limiting factor in ecosystems Nitrogen is lost from soils via leaching and runoff Denitrifying bacteria convert nitrates and nitrites to nitrogen gas

Phosphorus Cycle

Phosphorus is part of phospholipids and all nucleotides It is the most prevalent limiting factor in ecosystems Main reservoir is Earth’s crust; no gaseous phase

Phosphorus Cycle

mining FERTILIZER excretion uptake by autotrophs GUANO weathering MARINE FOOD WEBS DISSOLVED IN OCEAN WATER death, decomposition sedimentation settling out MARINE SEDIMENTS weathering agriculture uptake by autotrophs DISSOLVED IN SOILWATER, LAKES, RIVERS death, decomposition LAND FOOD WEBS leaching, runoff uplifting over geologic time TERRESTRIAL ROCKS

Figure 48.23, Page 884

Human Impact on Ecosystems

Increased Eutrophication of Lakes Increase in nutrient levels (phosphates, nitrates, etc.) Can lead to algal blooms Hypoxia What is it?

Why?

Can lead to the eventual loss of fish and other aquatic organisms 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 Toxins that are lipophilic cannot be excreted in urine (water!), so they are stored in fatty tissue (adipose tissue) unless the organism has enzymes to break it down Important examples?

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 Atmosphere Burning fossil fuels (wood, coal, oil) releases CO 2 Carbon dioxide and water in the atmosphere retain solar heat, causing the greenhouse effect

Human Impact on Ecosystems

Use of chlorofluorocarbons has destroyed ozone (O 3 ) by converting it to oxygen gas.

Ozone protects against UV radiation Increasing skin cancers, cataracts What are your odds of getting skin cancer in your lifetime?

Rain Shadow

Air rises on the windward side, loses moisture before passing over the mountain Leeward side is in the rainshadow; deserts

Figure 49.7

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Biomes

Regions of land characterized by habitat conditions and community structure Distinctive biomes prevail at certain latitudes and elevations

Tropical Forests

May be dry, deciduous, or rainforests T. Rainforest Abundant rainfall 4 layers to forest (upper & lower canopy, shrub understory, & herbaceous layer) Poor soil due to leaching Highest species diversity

Grasslands

Savannas Tropical & subtropical with scattered trees 3 seasons: cool & dry; hot & dry; warm wet.

Frequent fires Grazing mammals (African grasslands)

Chaparral

Along coastlines in mid latitudes Mild, rainy winters & hot, dry summers Evergreen shrubs Periodic fires Browsers, rodents reptiles

Temperate Grassland (Prairie)

Similar to savannah without trees Cold winters Maintained by fire Seasonal drought Rich soils Grazing animals; herbivores

Temperate Deciduous Forest

Our biome 3 layered forest Dominant species are deciduous trees Midlatitudes

Deserts

Less than 10 centimeters annual rainfall, high level of evaporation Tend to occur at 30 degrees north and south and in rain shadows One-third of land surface is arid or semiarid

Arctic Tundra

Occurs at high latitudes Permafrost lies beneath surface Nutrient cycling is very slow Coldest biome Low species diversity Do not post on Internet Arctic tundra in Russia in summer Figure 49.19

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Taiga (coniferous forest)

Found in northern latitudes Harsh winters; short summers Thin, acidic soil Coniferous trees No permafrost

Alpine Tundra

Occurs at high elevations No underlying permafrost Plants are low cushions or mats as in Arctic tundra

Do not post on Internet Figure 49.19

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Lakes

Bodies of standing freshwater Eutrophic: shallow, nutrient-rich, has high primary productivity, Oligotrophic: deep, nutrient poor, has low primary productivity

LITTORAL

Lake Zonation

LIMNETIC PROFUNDAL LITTORAL Figure 49.21

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Thermal Layering

In temperate-zone lakes, water can form distinct layers during summer THERMOCLINE

Figure 49.22

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Seasonal Overturn

In spring and fall, temperatures in the lake become more uniform Oxygen-rich surface waters mix with deeper oxygen-poor layers Nutrients that accumulated at bottom are brought to the surface

Ocean Provinces

neritic zone oceanic zone intertidal zone Figure 49.24

Page 906 continental shelf BENTHIC PROVINCE bathyal shelf PELAGIC PROVINCE 0 200 1,000 2,000 abyssal zone hadal zone 4,000 deep-sea trenches 11,0000 depth (meters)

Phytoplankton

Floating or weakly swimming photoautotrophs; form the base for most oceanic food webs Ultraplankton are photosynthetic bacteria

Hydrothermal Vents

Openings in ocean floor that spew mineral-rich, superheated water Primary producers are chemoautotrophic bacteria; use sulfides as energy source

Do not post on Internet Tube worms at hydrothermal vent Figure 49.26

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Estuary

Partially enclosed area where saltwater and freshwater mix Dominated by salt-tolerant plants Examples are Chesapeake Bay, San Francisco Bay, salt marshes of New England

Estuarine Food Webs

Primary producers are phytoplankton and salt tolerant plants Much primary production enters detrital food webs Detritus feeds bacteria, nematodes, snails, crabs, fish

Intertidal Zones

Littoral zone is submerged only during highest tides of the year Midlittoral zone is regularly submerged and exposed Lower littoral is exposed only during lowest tides of the year

Rocky Intertidal

Grazing food webs prevail Vertical zonation is readily apparent Diversity is greatest in lower littoral zone

Figure 49.29

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Upwelling

Upward movement of water along a coast; replaces surface waters that move away from shore

Figure 49.31

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