Chapt02 Lecture Modified

8/12/2019 Chapt02 Lecture Modified

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Principles of Ecology:

Matter, Energy, and Life

Chapter 2


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Outline:

Food Webs

Ecological Pyramids

Biogeochemical Cycles


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Sunlight

Solar energy that reaches the earths surface

is in, or near, the visible light wavelengths.

Drive photosynthesis.

More than half of the incoming sunlight maybe reflected or absorbed by atmospheric

clouds, dust, or gases.

Short wavelengths are filtered out by

gases in the upper atmosphere.


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Photosynthesis and Respiration

Photosynthesis

6H2O + 6CO2 + sunC6H12O6 (sugar) + 6O2

Cellular Respiration

C6H12O6+6O26H2O + 6CO2+ energy


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Energy Exchange


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Energy and Matter in the Environment

Species- All organisms genetically similar

enough to breed and produce live, fertile

offspring in nature.

Population- All members of a species that

live in the same area at the same time.

Biological Community- All populations living

and interacting in an area.

Ecosystem- A biological community and its

physical environment ( water, mineral

resources,air, sunlight etc.)


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Much of ecology is concerned with understanding

the ways energy and matter move through anecosystem

In an ecosystem, there is interaction between thebiotic and abiotic factors.

The study of an ecosystem involves how energyflows from one sytem to another.

An open ecosystem is a system in which animalscan move from one area to another without aboundary (energy also moves)

A closed ecosytem does not allow cross over (energy does not move)


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Food Chains, Food webs & Trophic Levels

Photosynthesis provides all the energy for

all ecosytems.

One of the major property of an ecosystem

is productivity ( amount of biomass) in a

given area in a given time.

Photosynthesis is called as the primary

productivity in an ecosystem.


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Food Webs and Trophic Levels

Productivity refers to the amount of biomassproduced in a given or during a given time.

Primary Producersorganisms whophotosynthesize e.g plants

Consumersorganisms who do notphotosynthesize, they get their energy byeating other organisms.

Food Websare series of interconnected foodchains in an ecosystem.Some consumersfeed on single sps., others have multiple foodsources (Fig 2.13).


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Ecological Food Chain


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Trophic Levels

An organisms feeding position in an ecosytem is

called as trophic level.

Organisms can also be identified by the kinds of

food they consume:

Herbivores cows eat plants. Carnivoreslion eat animals.

Omnivores- man eat plants and animals.

Detritivoresants & beetles eat detritus ( litters) Decomposers- bacteria and fungi breakdown

complex organic matter into simpler compounds.


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Note position of each organism in this food chain:

A corn plant ( primary producer) is eaten by agrasshopper ( primary consumer)

Chicken (secondary consumer )eats thegrasshopper

Man ( tertiary consumer ) (top carnivore)eats thechicken

Fungi and bacteria ( decomposers) feed on deaddecaying matter.

Energy is transferred from corn plants to man andwhen man dies, body decays and the decomposers

break down complex compounds to simpler onesreleasing the energyfood chain


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Ecological Pyramids

Most ecosystems have huge number of primary

producers supporting a smaller number ofherbivores, supporting a smaller number ofsecondary consumers.

Second law of thermodynamics ( a certain amount

of energy is lost / dissipated)- Ecosystems are not 100% efficient.

- E.g A prairie dog when eating grasses does notdigest all the plant parts efficiently. Moreoverenergy is also lost when he is running moresowhen a carnivore eats himhe does not eat theflesh completely..energy is lost in theecosystem.


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Ecological Pyramids


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BIOGEOCHEMICAL CYCLES

Hydrological Cycle

Most of earths water is stored in the

oceans, but solar energy continually

evaporates this water, and winds distribute

water vapor around the globe.

Water that condenses over land surfaces,

in the form of rain, snow or fog supports all

terrestrial ecosystem.


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Living organisms emit the moisture to the

atmosphere through respiration and

perspiration.

Eventually this moisture re- enters the

atmosphere or enters lakes and streams and

ultimately to the oceans.


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Hydrologic Cycle


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Carbon Cycle

Carbon serves a dual purpose for organisms:

Carbon is a structural component oforganic molecules (C6H12O6, sugar)

Chemical bonds provide metabolic energy.

The carbon cycle begins withphotosyntheric organisms that take up(CO2, carbon dioxide) to form starch.

Starch is taken up by several organisms,digested in stomach and simple sugars getbroken down to simpler ones (CO2 ,H20 &energy).


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Carbon cycle ( Contd.)

Sugar molecules either undergo respiration

and releases carbon in the form of C02.

Simple sugar can also form large organic

molecules such as cellular structrure of the

cells.

When the body decay carbon returns to

nature.

Dead decaying woods return their carbon

after bacteria and fungi feed on them.


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Fossil fuel (e.g coal and oil) , their carbon

atoms are not retuned to soil until they are

burnt.

Calcium carbonate (CaCO3) building

structure for many coral reefs also contribute

to the carbon cycle.

Limestones deposit in nature are biologically

formed from CaC03.


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Carbon Cycle


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The Nitrogen cycle

Several organic molecules contain nitrogen

Amino acids, peptides and proteins are large

organic molecules that living organisms need

for their existence.

Nitrogen is a very important nutrient for living

things.

Nitrogen is a primary component of many

household ( Ammonia and other detergents)

and agriculture fertilizers.


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Nitrogen Cycle ( Cont.)

Nitrogen makes up about 78% of the air, but

plants cannot use N2, the stable diatomicmolecule in air.

Plants acquire nitrogen through nitrogen

cycle. Nitrogen-fixing bacteria( live in roots of

legumes) and blue-green algae) arehighly organised to fix nitrogen of theatmosphere to Ammonia ( N2to NH3)

They combine hydrogen of atmospherewith Nitrogen and form Ammonia( NH3)


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The nitrogen cycle( Contd.)

Other forms of bacteria combine

atmospheric oxygen ( O2) with Ammonia

and form nitrites( NO2-).

Other forms of bacteria convert nitrites to

nitrates (NO3-),which green plants can

absorb and use.

After plants cells absorb nitrates, these

nitrates are reduced to Ammonia (NH3).

Ammonia in plants are used to make

amino acids which is used as building

blocks to form protein( a polypetptide


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Nitogen cycle (cont.)

Nitrogenenters the environment in many

ways:

Plants and animals die.

Fungi and bacteria decay dead organisms,

releasing the ammoniawhich is convertedback to nitrates.

Animals produce urine which is contain

nitrogenous compounds. Denitrifying bacteriabreaks down nitrates

to nitrogen ( N2) and nitrous oxide( N2O),gases released to atmosphre.


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Nitrogen Cycle


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Phosphorus Cycle

Abundant phosphorus stimulates plant and

algal productivity.

Major component of water pollution.

- Reduced levels of dissolved oxygen.


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Phosphorus Cycle


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Sulphur Cycle

Sulphur is an essential component of

proteins for living organisms.

Sulphur compounds determine the acidity of

rainfall, surface water and soil.

Sulphur is tied up in soil as mineral rocks.

Weathering or emission from deep seafloor

vent or volcanic eruption releases sulphur.


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Sulfur Cycle

Sulfur compounds are important

determinants of the acidity of water.

Particulates may also act as critical

regulators of global climate.

Sulfur cycle is complicated by a large

number of possible oxidation states.

Sulphur is oxidised to sulphur dioxide,

sulphate or hydrogen sulphide.


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Sulhur cycle Contd.

Human activities also releases a large

quantity of sulphur, primarily through

burning fossil fuels

Sulphur dioxide and sulphate causes

human health problems.

When ocean water warms up, tiny

organisms produces

dimethylsulphide(DMS) which oxidisessulphur dioxide and then sulphate to the

atmosphere.

Sulfur Cycle


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Sulfur Cycle


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Chapt02 Lecture Modified