Ecosystems

Unit 3 – Chapter 3

Energy

The capacity do to work or to transfer heatKinetic – energy of motion

Heat: movement of particles w/i a given substanceElectromagnetic: moves in the form of a wave as a result in changes in electric and magnetic fields

Potential – stored energyWater in a reservoir behind a dam, the chemical energy stored in carbon atoms of fossil fuels, food

Energy

99% of energy on earth comes from the sunWind, hydropower, biomass are all still forms of solar power1% comes from commercial energy (locally from burning coal)The quality of the energy is important

High quality = high capacity to do useful work Low quality = little capacity to do work

Law of Thermodynamics

1st Law aka Law of conservation of energy: whenever energy is converted from one form to another, no energy is created or destroyed.2nd Law: whenever energy is converted from one form to another in a physical or chemical change, we end up with lower-quality or less usable energy than we started with.

System

Set of components that function and interact in some regular way (Human body, rivers, the economy)Key components

InputsFlows or throughputsOutputs

Feedback

Feedback is any process that increases or decreases a change to a systemFeedback loop – occurs when an output of matter, energy, or information is fed back into the system as an input and leads to changes in that system

Feedback Loops

Negative Feedback loopsCauses a system to change in the opposite directionAlmost all human body feedback loopsThermostats Recycling of aluminum

Positive Feedback loops causes a system to change further in the same directionOnly two in the human bodyGreat concern in environmental systems (polar ice)Deforestation = erosion & nutrient loss= vegetation loss = erosion & nutrient loss = more vegetation loss

Nutrient cycles or biogeochemical cycles

The movement of elements and compounds through each component of the ecosystem or biosphere including the soil, rock, air, and water.Five major cycles

Water (hydrologic)CarbonNitrogenSulfurPhosphorus

Human activities alter these biogeochemical cycles.When nutrients are stored in the atmosphere, ocean, or underground deposits, they are said to be in reservoirs.

Unique properties of waterPolar – universal solventHydrogen bonding – holds water molecules togetherHigh boiling pointCan store a large amount of heat without a large change in its own temperatureWater filters out UV radiation that may be harmful to aquatic organisms, yet transparent which allows photosynthesisSurface tension – capillary action (attraction b/w water molecules)Expands when frozen, which means ice freezes on the top of rivers or lakes rather than throughout which protects aquatic life within

Water CycleCollects, purifies, and distributes the earth’s fixed supply of water (ecosystem service)

Evaporation acts as a natural distillation process that removes impurities from the waterWater flowing through streams, lakes, and underground aquifers are naturally filtered and partially purified by chemical and biological processes (primarily decomposer bacteria) as long as the system is not overloadedPrecipitation delivers partially distilled water to organisms

Powered by the sunTransports nutrients within and between ecosystems due to the polarity of water and its property as the universal solvent

Three Major Processes• Evaporation: liquid to gas that is held in the atmosphere

• Comes from soil, bodies of water such as lakes and oceans, and transpiration

• Precipitation: gravity enables water to fall back to the earth’s surface in the form of rain, snow, sleet, and dew

Most precipitation becomes surface runoff which flows back into streams, rivers, and eventually the oceanSome soaks into the soil and is used by plantsSome evaporates againSome is stored long-term as glaciersSome seeps through permeable rock formations to underground aquifers where it is stored as groundwater

Transpiration: plants lose water through their leaves

Human effects on the water cycle1. Withdrawal of large quantities of freshwater

from streams, lakes, and aquifers at rates faster than nature can replace it.

2. Clear vegetation for agriculture, mining, roads, and other forms of development. Then we cover much of the land with concrete, asphalt, and buildings, which increases runoff and decreases the amount of water than sinks into the soil to replenish groundwater supplies, increases topsoil erosion, and increases the risk of flooding.

Human effects on water cycle cont.3. Destruction of wetlands for farming and urban

development leads to increased flooding. Wetlands provide natural flood control (ecosystem service) by absorbing the overflow of water.

Water Cycle Animation

Write down the terms located in the top left corner of the animation box as you listen and watch the following animation

Fig. 3-16, p. 67

Condensation Condensation

Ice and snow

Transpiration from plants

Precipitation to land Evaporation of

surface water Evaporation from ocean

Runoff

Lakes and reservoirs Precipitation

to oceanRunoff

Increased runoff on land covered with crops, buildings and pavementInfiltration and

percolation into aquifer

Increased runoff from cutting forests and filling wetlands

Runoff

Groundwater in aquifers

Overpumping of aquifers

RunoffWater pollution

Ocean

Natural process

Natural reservoir

Human impacts

Natural pathwayPathway affected by human activities

Carbon CycleCarbon is the basic building block of carbohydrates, fats, proteins, and DNA.The circulation of carbon containing compounds throughout the biosphere, atmosphere, and hydrosphere make up the carbon cycle.Carbon dioxide (CO2) gas is the most important component of the carbon cycle.Changes in CO2 levels from natural or man-made causes affect the earth’s climate

Regulates the atmospheric temperatureIncreased levels = higher temperatureDecreased levels = lower temperature

Carbon Cycle cont.

Producers in both terrestrial and aquatic habitats remove CO2 from the atmosphere by utilizing it during the photosynthesis process converting CO2 into glucoseOxygen-consuming producers, consumers, and decomposers then carry out aerobic respiration which is the reverse of photosynthesis and breaks the glucose down into CO2 for reuse by producers

Photosynthesis and respiration

Producers are necessary to remove carbon from the atmosphere; consumers and decomposers are needed to return carbon to the atmosphere.

Photosynthesis 6 CO2 + 6 H2O + solar energy C6H12O6 + 6 O2

Aerobic Respiration C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy

Carbon cycle and carbon sinks

Some carbon atoms are decomposed on land and are then returned immediately to the atmosphere.In aquatic systems, organisms that are decomposed then form insoluble carbonates that sink to the bottom of the ocean, where they are stored for very long periods of time.The largest deposit of carbon is located in ocean sediments..

Production of fossil fuelsEventually over extremely long periods of time, buried deposits of organic material are compressed b/w layers of sediment and fossil fuels are forms such as coal, oil, and natural gasFossil fuels are reservoirs of carbon until such time as they are extracted and then burned, which released carbon dioxide into the atmosphere once again.Fossil fuels are non-renewable

Human impacts on the carbon cycle

1. Adding large amounts of CO2 by burning fossil fuels (using fossil fuels faster than they can be replaced)

2. Deforestation removes trees which provide the natural service of absorbing and storing carbon (ecosystem service) at a faster rate than they can be replaced

3. Altering both the rate of energy flow and the cycling of nutrients within the carbon cycle

Atmospheric Warming

Carbon dioxide (CO2), methane (CH4), and other greenhouse gases are likely to warm the atmosphere by enhancing the planets natural greenhouse effect and thus change the earth’s climate during this century.

Write down the terms located in the top left corner of the animation box as you listen and watch the following animation

Carbon Cycle Animation

Nitrogen

Our atmosphere serves as the largest reservoir for nitrogen is the atmosphere78% of our atmosphere is diatomic nitrogen N2

Component of nucleic acids, proteins, and DNADiatomic nitrogen (N2) can’t be used directly by plants and animals – it must be processed into usable forms

2 processes that “fix” nitrogen Lightning and nitrogen fixing bacteria

Lightning takes place in the atmosphereDiatomic molecules are broken apart by the energy of the lightning This allows individual nitrogen atoms to combine with oxygen to form nitrogen oxidesThese nitrates eventually return to earth during rain events

Nitrogen Fixing BacteriaSpecialized bacteria and cyanobacteria (blue-green algae) combine N2 gas with hydrogen to form ammonia (NH3)The bacteria use some ammonia as nutrients and convert it into a waste product – ammonium ions (NH4

+)NH3 and NH4

+ not taken up by plants immediately converted to nitrate ions (NO3

-) through the process of nitrificationPlants easily absorb NO3

- ions where the ions are incorporated into amino acids, nucleic acids

Nitrogen use by non-producers

Animals cannot use any of the atmospheric nitrogen, nor the nitrogen found directly in the soil, therefore they must get their nitrogen from the plants they consume, or from the plant-eating animals they consumeDecomposers and detritivores also get their nitrogen needs from consuming organisms that contain nitrogen (plants or animals)

Nitrogen CyclePlants and animals return nitrogen-rich organic compounds to the environment as waste, as well as cast-off particles of skin, leaves, hair or when they die and are decomposed or scavenged.Ammonification – decomposer bacteria convert detritus into simple forms of nitrogen compounds such as NH3 and NH4

+

Denitrification – specialized bacteria in swamps and bottom sediments convert NH3 and NH4

+ back into nitrate ions (NO3

-) and then into nitrogen gas (N2) or nitrous oxide gas (N2O)These gases return to the atmosphere

Human Impacts on the Nitrogen Cycle1. We add large quantities to nitric oxide (NO) to

the atmosphere from the combustion of fuel at high temperature. This turns into nitrogen dioxide (NO2) in the atmosphere which combines with water to form nitric acid (HNO3)

2. We add nitrous oxide (N2O) to the atmosphere through the action of anaerobic bacteria on fertilizer (both commercial and animal manure) spread for agricultural purposes

3. We release large quantities of nitrogen through deforestation, destruction of grasslands and wetlands.

Human Impacts on Nitrogen Cycle

4. Agricultural runoff contributes large amounts of nitrates directly into streams, rivers, and lakes, which leads to algae blooms (overgrowth)

5. Harvesting of nitrogen rich crops, withdraws nitrogen compounds from the soil; irrigation of croplands leads to nitrogen poor soil b/c it washes nitrates out of the soil; burning and clearing grasslands and forests for agriculture lead to nitrogen loss

Mississippi River Sedimentation plume from river runoff

Human Impacts cont.

Since 1950 we have doubled the annual release of nitrogen into the atmosphere The amount is expected to double again by 2050Nitrogen overload is a serious problem in both aquatic and atmospheric regions.

Write down the terms located in the top left corner of the animation box as you listen and watch the following animation

Nitrogen Cycle Animation

Phosphorus Cycle

Only occurs in the terrestrial and aquatic regions – not in the atmospherePrimary component - phosphate ions (PO4

3-)Primary reservoirs: terrestrial rock formations and ocean sediments (floor of ocean)Slow compared to Carbon, Nitrogen, and Water cycles

Phosphate reservoirs

Phosphates can leave the cycle for long periods of time when they are washed into the ocean and then stored in bottom sediment for millions of yearsUplifting movements then expose the rock formations for erosion once again

Phosphorus Cycle

Water flows over rock which erodes inorganic phosphate containing compounds and carries them into soil, where they are absorbed by plantsPhosphate ions can also be transferred through food webs from producers to consumers to decomposers and detritivoresImportant for nucleic acids and production of ATP and ADP; production and maintenance of bones and teeth

Phosphate in soils and water

Most soils are phosphate poorActs as a limiting reactant for growth of plants unless phosphates are added in the form of fertilizerPhosphate salts are only slightly soluble in water, so they may also act as limiting reactants for the growth of producer populations in freshwater streams and lakes

Human Impacts on Phosphorus Cycle

1. Removing large amounts of phosphates from rocks (mining) in order to produce fertilizer

2. Clearing forests causes topsoil erosion, which depletes already limited quantities of phosphorus

3. Runoff from land clearing leads to algae blooms, decreased dissolved oxygen, and eutrophication of freshwater lakes

Lake Eutrophication and Nitrogen and Phosphorus Cycles

Eutrophication: physical, chemical, and biological changes that take place after a lake, estuary, or slow-flowing stream receives inputs of plant nutrients – mostly nitrates and phosphates – from natural erosion and runoff from the surrounding land basin.Cultural Eutrophication: Overnourishment of aquatic ecosystems with plant nutrients (mostly nitrates and phosphates) because of human activities such as agriculture, urbanization, and discharges from industrial plants and sewage treatment plants

The detergent controversy1960s and 1970s phosphate based detergents were widely usedThe purification processes used in wastewater treatment plants did not remove phosphates and nitrates, as they are naturally occurring and relatively harmless Some rivers and lakes had foamy surfaces due to effluent dischargeMassive algae blooms and increased eutrophication resultedPhosphates were removed from all laundry detergents in 1994; 16 states have banned phosphates in dishwashing detergents

Algae overgrowth from phosphate and nitrate runoff

Increased phosphate levels create massive algae bloom

Write down the terms located in the top left corner of the animation box as you listen and watch the following animation

Phosphorus Cycle Animation

Sulfur CycleOccurs throughout the terrestrial, aquatic, and atmospheric components of the biosphereStored primarily in rocks and minerals in the form of sulfate salts (SO4

2-) under ocean sedimentsSulfur enters the atmosphere in several ways:

Hydrogen sulfide gas (H2S) – volcanoes and decomposition in swamps, bogs, tidal flatsSulfur dioxide (SO2) – volcanoes Particulate sulfate salts (SO4

2-) - sea spray , dust storms, forest firesDimethyl sulfide (DMS) – produced by marine algae

Sulfur Cycle

Sulfur is taken up by plants, consumed by animals, then transferred to decomposers during food web exchangesSulfur enters the atmosphere through natural and human sources, combines with water vapor to form acid deposition which harms trees and aquatic lifeSulfur ions can react with metal ions to form insoluble metallic sulfides which are deposited as rock or metal ore, which is then mined and the cycle continues

Human Impacts on the Sulfur Cycle

Largest impact is the release of sulfur into the atmosphere

Burning of sulfur containing fossil fuels (coal and oil) for electric powerRefining of sulfur containing fossil fuels (petroleum) to make a wide array of petroleum products (gasoline, diesel, heating oil)Extraction of metals such as copper, zinc, and lead from sulfur containing compounds

Write down the terms located in the top left corner of the animation box as you listen and watch the following animation

Sulfur Cycle Animation

Nutrient Cycles

Nutrient cycles provide nutrients to all living organismsThese cycles are driven by gravity, solar energy, and the complex nature of food websHuman activities are degrading natural resourcesThese activities are altering the flow of energy throughout the biosphere and altering the rate at which the nutrients cycle

Earths 4 major spherical systemsAtmosphere

Troposphere - 17 km above sea level at the equator, 7 km above sea level at the poles

All of the earths “weather” occurs hereAir we breathe: 78% N2 , 21% O2, 1% greenhouse gases (H2O vapor, CO2, CH4)Greenhouse gases are necessary to keep the planet from freezing, these gases absorb and release energy that warms the lower atmosphere

Stratosphere – 17 to 50 km above the surface of the earth

Holds ozone (O3) which filters out 95% of the suns harmful UV radiation

Earths 4 major spherical systemsHydrosphere

All water on or near the surface of the earth3 states of matter:

vapor in air, liquid on surface and below ground, solid in polar ice, icebergs, glaciers, ice in frozen soil layers

Oceans contain 97% of water on Earth and cover 71% of the earths surfaceLeaves only 3% as freshwater

Earths 4 major spherical systems

Geosphere Rock, soils, and sedimentsCore – intensely hot centerMantle – mostly rockCrust – thin outer layerUpper portion contains non-renewable resources such as fossil fuels, minerals, and renewable nutrients,

BiosphereAny part of the planet where life is found (includes hydrosphere, atmosphere, and geosphere)

3 Factors for sustaining life

One-way flow of high-quality energyCycling of nutrientsgravity

Top Five Greenhouse gases

Water vaporCarbon dioxideMethaneNitrous oxideOzone

Anthropogenic contributions of greenhouse gases

Burning carbon-containing fossil fuels releases huge quantities of CO2 into the atmosphereGrowing crops and raising livestock release large quantities of CH4 and N2O

Energy Flow to the EarthNuclear fusion in the sun produces huge amounts of solar radiationOnly a small amount reaches the earth in the form of EM waves; visible light, UV radiation, and heatMuch of this energy is absorbed or reflected back into space by the earths atmosphere and surfaceAbsorption

Solar E that reaches our atmosphere warms the air, and is responsible for nutrient cyclingApproximately 1% of the energy generates winds that are responsible for our weather patternsProducers use solar energy to produce the nutrients they need through photosynthesis

Energy Flow to the Earth

ReflectionApproximately ½ of the initial radiation makes it to the planets surface where it is degraded to lower quality energy after its interaction with land, water, or organismsThe rest is reflected back into spaceAs the radiation is traveling back towards space, greenhouse gases (absorb some of the energy which cause the molecules to vibrate faster (see KMT) which creates heat that warms the earth’s lower atmosphere (This is known as the natural greenhouse effect)

Organization of Ecosystems

Ecology – science that focuses on how organisms interact with each other, the non-living environment of energy and matterOrganization of Ecosystems

OrganismsPopulationsCommunities

Living and non-living components

Biotic – living componentsAbiotic – non-living componentsTrophic levels – the feeding level of an organism based on its source of food or nutrients

Producers/Autotrophs

Make their own nutrientsPhotosynthesis

Plants absorb solar energy, take carbon dioxide out of the air, and add water molecules to form glucose and oxygen6 CO2 + 6 H2O + solar energy C6H12O6 + 6 O2 Terrestrial = plantsAquatic = algae and plants near shorelines; open ocean = phytoplankton

Aquatic Producers

Producers/Autotrophs

ChemosynthesisSpecialized bacteria convert simple inorganic compounds from their environment into more complex nutrient compounds without using sunlightHydrothermal vents on the ocean floor produce very warm water areasBacteria are able to use hydrogen sulfide gas (H2S) to produce complex carbohydrates

Chemosynthetic bacteria hydrothermal vents video clip

Consumers/HetertrophsThese organisms must obtain the energy they need by consuming producers, other consumers, or their remainsAll consumers depend on producers for their nutrientsTypes of consumers

Primary consumersHerbivores – animals that eat mostly green plants

Types of consumers cont.Secondary

Carnivores – eat flesh of other consumers, primarily herbivoresFoxes, insect eating songbirds, snakes, lions

TertiaryCarnivores that frequently feed on the flesh of other carnivoresTigers, killer whales, sharks, big fish, hawks

*The prey that was consumed dictates the level of consumer, some organisms can be secondary and tertiary consumers*Sometimes the levels are represented through the quaternary level (4th level)

Types of Consumers cont.Omnivores – eat plants and animalsDecomposers

Consumers that release nutrients from the wastes or remains of plants and animals and then return those nutrients to the soil, water, and air for reuse by producersBacteria and fungiDetritus feeders/detritivores

Feed on the wastes or dead bodies of other organismsEarthworms, insects, vulturesProvides the ecosystem service of cycling nutrients and removing excess plant debris, animal wastes, dead bodies and garbage

Time Lapse Decomp of Rabbit

RespirationAerobic

Process through which energy from glucose is releasedUses oxygen to convert glucose back into carbon dioxide and waterThe net chemical change of aerobic respiration is the opposite of photosynthesis

Anaerobic/fermentationProcess through which energy from glucose is releasedOccurs in the absence of oxygenProduces methane, ethyl alcohol, acetic acid and hydrogen sulfide gas

*Note that all organisms get their energy from respiration, but only plants and phytoplankton carry out photosynthesis

Food Chains and Food Webs

Food Chain – the order in which organisms consume one another (linear)Food Web – the complex interactions of multiple food chains which show the complexities of those interactions (non-linear)

Energy Flow through Ecosystems

Food chains and webs show how energy is transferred between members of ecosystems at different trophic levelsAs the trophic (feeding) level increases the amount of high-quality energy available decreasesSome of the energy is lost as heat at each step.

Biomass – multiple definitions1. The dry weight of all organic matter contained

in its organisms2. Organic matter produced by plants and other

photosynthetic producers3. Total dry weight of all living organisms that can

be supported at each trophic level in a food chain or web

4. Dry weight of all organic matter in plants and animals in an ecosystem

5. Plant materials and animal wastes used as fuel

Energy Transfer

Approximately 90% of high-quality energy is lost in each step of the food chain or webThe large loss in chemical energy explains why food chains and webs rarely have more than 3 or 4 levels.As a result of energy loss, there are few tertiary or quaternary consumers as compared to producers and primary consumers.

Production of Biomass is a measure of productivity

The amount of biomass is that can be produced is the result of available solar energy and how quickly it can be produced from the organisms living in the ecosystemGross Primary Productivity (GPP) is the rate at which an ecosystem’s producers convert solar energy into chemical energy stored in biomass

Measured in kcal/m2/yr (E production per unit area over a given time)

Net Primary Productivity (NPP) is the rate at of photosynthesis minus the rate of aerobic respiration

Productivity varies by ecosystem

NPP

Producers are the source of all nutrientsOnly biomass represented as NPP is available as nutrients for consumers The planet’s NPP ultimately limits the number of consumers (including humans) that can survive on earth