Lecture 15

Lecture 15: Ecosystems

Covers Chapters 28 & 29

Ecosystem

• All of the living and non-living components of a defined geographic area*

Ecosystem Function

• Two basic laws*:

• Energy moves through ecosystems in a continuous one-way flow– Energy is constantly replenished because it is

converted to heat that radiates up into space

• Nutrients constantly cycle and recycle within and among ecosystems– Nutrients can change form, but remain on Earth

Flow of ENERGY

• Energy enters communities mostly through photosynthesis

• Plants use sunlight and inorganic nutrients it takes from the abiotic (non-living) environment to make ATP and glucose, can also make proteins, fats & nucleic acids

• Byproduct of photosynthesis is oxygen

O2

CO2

H2O

sugar

plant tissues

othernutrients

energy from sunlight

photosynthesis

Fig. 28-1

Energy passed from one trophic level to another in an ecosystem*• Producers: autotrophs (self-feeding organisms)

make their own food (photosynthesis)• Consumers: heterotrophs (other-feeding

organisms) get energy and nutrients from producers and other organisms

• Energy is lost as it passes from one level to another, so plants actually dominate most ecosystems because they have the most energy available to them!

But how much energy is there in an ecosystem?

• Net Primary Production: The energy that photosynthetic organisms (producers) store and make available to other members of the community

• NPP will determine the amount of life that can be supported in the community

• NPP influenced by*:

– Nutrients available

– Amount of sunlight

– Amount of water

– Temperature

Transition

• Now we discuss the “players” in the ecosystem and how they use energy/nutrients

How do nutrients/energy flow through an ecosystem? Producers/Consumers/Decomposers: overview*

• Producers: plants

• Primary consumers: feed directly ON PRODUCERS

– Herbivores: animals that eat plants only

– Called primary consumers

• Secondary consumers: prey ON PRIMARY CONSUMERS

– Carnivores: animals that eat other animals

– There can be tertiary, quaternary consumers, etc

• Detritus feeders: live on dead organic matter (dead organisms, fallen leaves/fruit, and waste-POOP!)

– Extract energy from the matter and excrete it in small pieces

• Decomposers: digest food outside of their bodies by secreting enzymes

– Feed on the excreted matter from detritus feeders

– Recycle the nutrients into the soil

Energy Flow, Nutrient Cycling, and Feeding Relationships

Fig. 28-2

solar energy

heat

heat

heat

heat

nutrients

heat energyenergy stored inchemical bonds

detritus feedersand decomposers

primaryconsumers

higher-levelconsumers

producers

energy fromsunlight

nutrients

OSPN

Mg HCa

H2O

Feeding relationships within ecosystems

• Food Chain: linear feeding relationship – one representative at each trophic level (A SINGLE PATH SHOWING ONE ANIMAL EATING THE NEXT)

• Food Web: each food chain is part of the web (SHOWS MULTIPLE CHAINS AND HOW THEY INTERACT)

• Each ecosystem has a different food chain/web

Food Chains on Land

Fig. 28-4a(a) A simple terrestrial food chain

tertiary consumer(4th trophic level)

producer(1st trophic level)

primary consumer(2nd trophic level)

secondary consumer(3rd trophic level)

Food Chains in the Sea

Fig. 28-4b(b) A simple marine food chain

quaternary consumer(5th trophic level)

tertiary consumer(4th trophic level)

producer(1st trophic level)

primary consumer(2nd trophic level)

zooplanktonphytoplankton

secondary consumer(3rd trophic level)

Chain vs Web

Food Web

Fig. 28-5

Flow of NUTRIENTS

• *Macronutrients: required by organisms in LARGE AMOUNTS

– Water

– Carbon

– Hydrogen

– Oxygen

– Nitrogen

• Micronutrients: required in SMALL AMOUNTS

– Zinc and other elements

Nutrient Cycles

• Describe pathways that nutrients follow between communities and the non-living portion of the ecosystem– Reservoirs: sources of and storage sites for

nutrients

• Hydrologic Cycle

• Carbon Cycle

• Nitrogen Cycle

• Please know how each nutrient ENTERS the cycle

Hydrologic Cycle• Pathway that water takes as it travels from its major reservoir (the

ocean – but lakes and rivers are also reservoirs) through the atmosphere*

• Impt because many nutrients must be dissolved in water before they can be used

– Solar energy evaporates water in ocean, lakes, rivers and it becomes precipitation*

– Precipitation hits the Earth

• Some evaporates back to atmosphere

• Some enters underground aquifers (silt, sand, gravel that is saturated with water)

• Plants absorb water, then it evaporates out through their leaves

evaporationfrom land andtranspirationfrom plants

reservoirsprocesses

water vapor inthe atmosphere

precipitationover land

extraction foragriculture

groundwater,includingaquifers

evaporation fromlakes and rivers

evaporationfrom the

ocean

precipitationover the ocean

runofffrom riversand land water in

the ocean

lakes and rivers

seepage into soil

The Hydrologic Cycle

Fig. 28-7

Carbon Cycle

• Movement of carbon from its major short-term reservoirs, through producers, into the bodies of consumers, detritus feeders, decomposers, and then back to its reservoirs*

• Recall that carbon is one of the building blocks of all organic molecules

Carbon Cycle– Enters communities through capture of CO2 during

photosynthesis*

– Primary consumers eat producers and acquire carbon stored in their tissues

– Consumers release CO2 as they breathe, excrete carbon in feces, and store some carbon (as sugars, etc.)

– Higher level consumers in turn get carbon from eating the bodies of lower level consumers OR bodies of dead organisms broken down by detritus feeders and decomposers

Fossil Fuels: byproduct of Carbon Cycle

• Much of the Earth’s carbon is bound in limestone rock, formed from calcium carbonate deposited on ocean floor in the shells of prehistoric phytoplankton

• Fossil fuels (coal, oil, natural gas) are formed from the remains of buried prehistoric organisms– Burning fossil fuel releases carbon into the

atmosphere as CO2

The Carbon Cycle

Fig. 28-8

reservoirs

processes

trophic levels

fire

consumers

respiration

CO2 in theatmosphere

CO2 dissolvedin the ocean

detritus feedersand decomposers

photosynthesis

producers

burningfossil fuels

fossil fuels(coal, oil, natural gas)decomposition

Nitrogen Cycle

• Nitrogen is a crucial component of proteins, vitamins and nucleic acids

• Our atmosphere is 78% nitrogen• Nitrogen moves from gas in atmosphere to

reservoirs of ammonia and nitrate in the soil and water

• It moves through producers and into consumers and detritus feeders, then returns to the atmosphere*

Nitrogen Cycle

• Nitrogen gas is converted to nitrate by a process called nitrogen fixation*: Bacteria in water and soil do this

• Then plants can use it• Consumers eat plants, then can utilize the nitrogen• Different bacteria can break down the nitrate

released in consumer’s feces and turn it back into nitrogen gas

reservoirs

processes

trophic levels

N2 in theatmosphere

ammonia andnitrates in water

decomposition

burningfossil fuels

uptake byproducers

application ofmanufactured fertilizer

consumers producers

denitrifyingbacteria

detritus feedersand decomposers

lightning

nitrogen-fixingbacteria in soil

and legume roots

ammoniaand nitrates

in soil

Fig. 28-9

Humans Disrupt Nutrient Cycles

• Fertilizer for plants is made from nitrogen gas and fossil fuels…..this is EXTRA nitrogen that is now dominating the nitrogen cycle.

• Water dissolves and carries away large quantities of nitrogen which drain into lakes and rivers and OVERSTIMULATES growth of phytoplankton

• Phytoplankton die and decomposing bacteria use up a LOT of oxygen to process the nitrogen

• Other aquatic animals die because of lack of oxygen

Humans Disrupt Nutrient Cycles

• Human activities release 10 billion tons of carbon (in the form of CO2) into the atmosphere– Burning fossil fuel– Deforestation reduces the amount of CO2 that

trees can process-leaving more CO2 in atmosphere

Global Warming due to greenhouse gases

• CO2 and nitrous oxide are two gases that are increasing in the atmosphere due to human disruption of carbon and nitrogen cycles

• These gases are trapped in atmosphere• Sunlight hitting the earth cannot bounce back to

atmosphere because gases are trapping the heat.• Result is rising Earth and water

temps….GLOBAL WARMING

Sunlight energyenters the atmosphere1

Most heat is radiatedback into space

Some energyis reflected backinto space

2

Some atmospheric heat isretained by greenhouse gases6

Most sunlight strikesEarth’s surface and isconverted into heat

3 Heat isradiated back intothe atmosphere

4

Sun

5

volcanoesforestfires

homes andbuildings

agriculturalactivities

vehicleemissions

power plantsand factories

Fig. 28-14

The more CO2 in the atmosphere, the warmer the Earth’s temp gets!

Fig. 28-15

Result of Global Warming*

• Glaciers melting

• Level of oceans are rising

• Extreme weather patterns (warmer earth causes disruption in normal air and water currents, altering weather patterns)

• Many species, used to living in areas with certain temp ranges, are moving due to higher temps

Fig. 28-17

You tube: global warming

• Global Warming 101: Nat Geo

The Earth’s climate*

• Weather: short term fluctuations in temp, humidity, cloud cover, wind and precipitation in a region over hours and days

• Climate: long term patterns of weather that prevail over years/centuries

• Each ecosystem has a different climate

What determines the Earth’s climate?*

• Amount of sunlight

• Amount of water

• Temperature ranges

• Earth’s curvature and distance of a certain region from the sun (sunlight strikes the earth most directly at the equator. Areas further north/south get less sun.)

• Air currents

• Ocean currents

• Elevation (air is thinner and cooler at higher elevations)

Climate (among other things) determine what kinds of organisms live in different ecosystems

• Appropriate temp is one condition of life (cannot be too hot/cold)

• Other conditions include availability of nutrients, water and energy

• Different types of organisms can exist within each ecosystem depending on the temperature of a specific ecosystem and the availability of nutrients, water and energy

– Ex: Desert communities are dominated by organisms that can adapt to extreme heat and lack of water

Environmental Demands Mold Physical Characteristics

Fig. 29-6

Rainfall and Temperature Influence the Distribution of Terrestrial Ecosystems

Fig. 29-7

high

low

precipitationlow

hot desert tropical deciduous forestsavanna and tropical scrub forest tropical rain forest

high

coniferous forest (taiga)

cool desert temperatedeciduous forest

temperaterain forest

grasslandchaparral

tundra

tem

pera

ture

Ecosystems can be divided into Biomes

• Large land areas with similar environmental conditions and characteristic plant communities*

• Biomes are defined by their plant life (since plants cannot move, they are PRECISELY adapted to the climate of the region where they are)

• Biomes named after the dominant type of vegetation in the area

Earth’s Biomes: See Handout

• Tropical Rain Forest

• Temperate Deciduous Forest

• Savanna

• Grassland/Prairie

• Chaparral

• Deserts

• Taiga

• Tundra

Fig. 29-8

Biomes/Biology/Ecology

• You Tube: great pacific media