Miller Lec 4

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CHAPTER 4

ECOSYSTEMS AND HOW

THEY WORK


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Ecology and Life

Ecology is study of how organisms interact

with one another and with their nonliving

environment

A species consists of all organisms -living

things-which can reproduce living offspring

Populations consist of organisms of same

species living in same place at same time

Genetically diverse organisms contribute

genes to the populations gene pool


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Ecology and Life -2

Several interacting populations occupying

the same habitat form a community

An ecosystem is the communities and their

nonliving environment; all Earths

ecosystems form the ecosphere

What are 6 characteristics of living thingsthat enable growth, survival and

reproduction?


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Reproduction and Evolution

While asexual reproduction can produce

new offspring - they are all identical

Sexual reproduction produces organisms

have new combinations of parental traits.

Traits which offer a better chance of

survival are adaptive and lead to evolution

Biodiversity refers to all of the variety of

living organisms and their traits


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Earths Life-support Systems

Atmosphere consists of inner trophosphere

and outer stratosphere

Hydrosphere is liquid, solid & gaseous

water

Lithosphere is crust and upper mantle

Ecosphere is portion of earth where

organisms interact (atmosphere,

hydrosphere, and upper lithosphere)


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Sustaining Life on Earth

Interconnected factors include:

one-way flow of high quality energy from sun;

What is the path?

Cycling of matter or nutrients through

ecosphere

Gravity permits earth to hold onto all parts ofecosphere


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Life is Sustained by Sun

Sunlight supplies energy for photosynthesis

Solar energy powers cycling of matter

Solar energy drives climate and weather

systems

Hydrogen and helium nuclei fuse releasing

solar energy


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Effects of Solar Radiation

Solar energy reaching earth is either

reflected (28%) or absorbed (28%)

Absorbed radiation warms, evaporated,

cycles, and generates winds.

Less than 1% is captured for photosynthesis

these reactions produce all organic

compounds required for all living organisms

Greenhouse effect - ultimate change of all

solar radiation to heat (infrared radiation)


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Ecosystem Concepts

Biomes are large terrestrial regions

characterized by distinct climate and

specific life forms.

Climate is weather - over the long term; it

determines type of life forms in biomes

Biomes contain many ecosystems

Aquatic life zones (like biomes) consist of

freshwater and marine life zones


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Major Components of Ecosystems

Abiotic - nonliving; water, air, nutrients and

solar energy

physical factors affecting terrestrial ecosystems

What are the six factors listed?

Physical factors affecting aquatic ecosystems

What are three factors listed?

Biotic - living componentsObserve how abiotic and biotic components

interact (fig. 4.9 and 4.10)


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Tolerance

Each population has range of variations in

environmental factors that it can tolerate; the

extremes of the range of tolerance are

tolerance limits.

Within this range of tolerance are variety of

conditions which are optimal for success.

State the law of tolerance

Some factors limit population growth more

than others - Name limiting factors in terrestrial and

aquatic ecosystems


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Biotic Components of Ecosystem

Producers (autotrophs) transform solar

energy into chemical energy of bonds of

organic molecules - Photo (&chemo)synthesisgreen plants and aquatic phytoplankton

Consumers (heterotrophs) cannot synthesize

organic molecules from scratch - they canconvert organic molecules from food to

other organic molecules needed


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Consumers

Consumers (heterotrophs) obtain energy

and nutrients from other organisms

Herbivores - primary consumers

Secondary & tertiary consumers may be:

carnivores - meat-eaters

omnivores - plant and meat eaters

scavengers and detritus feeders feed on animalsalready killed or remains of such

Decomposers - recycle organic molecules and

release inorganic molecules - biodegradation


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One-way Flow of Energy

Respiration is release of energy from

chemical bonds of organic molecules

Aerobic (w/oxygen) respiration --> complete

breakdown of glucose to CO2 + water +energy

Anaerobic (w/out oxygen) respiration (also

called fermentation) --> incomplete breakdown

of glucose --> methane, alcohol or acetic acid

One-way flow of energy through organisms

Matter & energy recycles through ecosystems


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Food Chains

Food chain - how nutrients and energy

move through organisms in ecosystem -

who eats who (Fig. 4-14)trophic levels begin with producers and end

with decomposers

Be sure you can identify types of organisms ateach trophic level, I.e. producers, primary,

secondary, and tertiary consumers


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Food Webs

Food web - network of interconnected food

chains; more complex because one

organism is never eaten by only one other Identify the various trophic levels shown in

Fig. 4.15


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Energy flow and Biomass storage

Biomass (dry weight of organic matter) is

transferred between trophic levels - but at

each level some biomass changes to energy

and is lost

Ecological efficiency compares biomass

transferred to that converted and lost

Pyramid of energy flow shows that firsttrophic level has greatest amount of energy

- some is transferred and some is lost at

each level


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Pyramid of Biomass

This pyramid demonstrates the total amount

of biomass at each trophic level

Why is biomass of producers less than thatof primary consumers in ocean ecosystem?


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Pyramid of Numbers

The actual number of organisms at each

trophic level - regardless of size (amount of

energy or biomass contained) Numbers of organisms at first level often

greatest and fourth level often has least

number of organisms - unless the producersindividually contain more biomass


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Primary Productivity

Gross Primary productivity - rate at which

producers convert solar energy into

chemical energy

Net Primary productivity - accounts forenergy that produces use for their own

respiration - biomass lost - so this rate is

always less Net primary productivity determines

carrying capacity of species in ecosystems


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Comparisons of net productivity

Which life zones have the greatest net

productivity? Why zones have the least?

Though tropical rain forest have highproductivity for natural plants, the

productivity when cleared is much less.

What effect have humans had on the earthsnet productivity?


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Matter Cycling in Ecosystems

Nutrients are any atoms, ions or molecules

needed by organisms to live, grow or

reproduce. Nutrient cycles (biogeochemical cycles)

show how elements needed in greatest

amounts travel through ecosystems


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Hydrologic (water) Cycle

Main processes:evaporation -liquid water to water vapor

transpiration - evaporation from plants

condensation - water vapor to liquid water

precipitation - water from air goes to land

infiltration - water moves into soil

percolation - water flows downward throughsoil

runoff - water flows downward across surface


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Hydrologic Cycle -2

Cycle powered by solar energy and gravity

Water vapor measurements: absolute vs.

relative humidity

Condensation requires condensation nuclei

and occurs at dew point

How does surface runoff affect lithosphere?

Name three ways Man has intervened in

water cycle.


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Carbon Cycle

Earths temperature varies with changes in

carbon dioxide in atmosphere and water

Producers use CO2 from atmosphere for

photosynthesis

Consumers release CO2 to atmosphere

Carbon of buried organisms may become

fossil fuels

Most carbon stored as limestone and in

water - How has Man disturbed carbon cycle?


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Nitrogen Cycles

Most is in gas form in atmosphere

Gaseous nitrogen must be fixed to form

ammonia or nitrates for plant assimilation

Plants synthesize nitrogen-containing

organic molecules -proteins & nucleic acids

Ammonia and nitrates converted back to gaswhich reenters atmosphere

How has Man intervened in nitrogen cycle?


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Phosphorus Cycle

There is no gaseous phase for phosphorus

Phosphorus circulates through water, earths

crust and living organisms

Phosphorus is added to land naturally by

guano and artificially by fertilizer

Phosphorus is limiting factor in growth ofmany organisms

How has Man intervened in phosphorus cycle?


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Sulfur Cycle

Much sulfur stored underground in rocks

and minerals

Sulfur enters atmosphere as hydrogensulfide, sulfur dioxide and sulfates

Water combines with sulfur dioxide to form

acid rain How has Man increased the atmospheric

phase of the sulfur cycle?


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Ecological Research

Field research - dirty, difficult and

expensive, but important; new technologies

Laboratory research - set up modelecosystems with controlled variables; easier

but must be coupled with field research

Systems analysis - computer simulationsused to make prediction; accuracy depends

on input


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Ecosystem Services and

Sustainability Ecosystem services constitute earths

natural capital; one is biological diversity:

genetic diversity - individuals in species vary ingenetic makeup

species diversity - habitats contain wide variety

of different species

ecological diversity - ecosystems contain wide

variety of communities


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Ecosystem Services and

Sustainability -2 Ecosystem services provide recycling,

purification and natural pest control

Each species results from many adaptations

Each species provides raw material for

future adaptation

Two basic principles of natural ecosystemsustainability: use renewable solar energy

and recycle nutrients efficiently

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