Transcript Principles of Ecology: Matter, Energy, and Life Chapter 2 1

Principles of Ecology:
Matter, Energy, and Life
Chapter 2
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Outline:
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Food Webs
Ecological Pyramids
Biogeochemical Cycles
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Sunlight
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Solar energy that reaches the earth’s surface
is in, or near, the visible light wavelengths.
 Drive photosynthesis.
More than half of the incoming sunlight may
be 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
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Photosynthesis
6H2O + 6CO2 + sun  C6H12O6 (sugar) + 6O2
Cellular Respiration
C6H12O6+6O2  6H2O + 6CO2 + energy
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Energy Exchange
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Energy and Matter in the Environment
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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 an
ecosystem
In an ecosystem, there is interaction between the
biotic and abiotic factors.
The study of an ecosystem involves how energy
flows from one sytem to another.
An open ecosystem is a system in which animals
can move from one area to another without a
boundary (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
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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
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Productivity refers to the amount of biomass
produced in a given or during a given time.
 Primary Producers – organisms who
photosynthesize e.g plants
 Consumers – organisms who do not
photosynthesize, they get their energy by
eating other organisms.
Food Webs are series of interconnected food
chains in an ecosystem.Some consumers
feed on single sps., others have multiple food
sources (Fig 2.13).
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Ecological Food Chain
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Trophic Levels
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An organism’s 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.
 Carnivores – lion eat animals.
 Omnivores - man eat plants and animals.
 Detritivores – ants & 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 a
grasshopper ( primary consumer)
• Chicken (secondary consumer )eats the
grasshopper
• Man ( tertiary consumer ) (top carnivore)eats the
chicken
• Fungi and bacteria ( decomposers) feed on dead
decaying matter.
• Energy is transferred from corn plants to man and
when man dies, body decays and the decomposers
break down complex compounds to simpler ones
releasing the energy…food chain
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Trophic Levels
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Ecological Pyramids
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Most ecosystems have huge number of primary
producers supporting a smaller number of
herbivores, supporting a smaller number of
secondary 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 not
digest all the plant parts efficiently. Moreover
energy is also lost when he is running …moreso
when a carnivore eats him…he does not eat the
flesh completely..energy is lost in the
ecosystem.
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Ecological Pyramids
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BIOGEOCHEMICAL CYCLES
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Hydrological Cycle
 Most of earth’s 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
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Carbon serves a dual purpose for organisms:
 Carbon is a structural component of
organic molecules (C6H12O6, sugar)
 Chemical bonds provide metabolic energy.
 The carbon cycle begins with
photosyntheric organisms that take up
(CO2, carbon dioxide) to form starch.
 Starch is taken up by several organisms,
digested in stomach and simple sugars get
broken down to simpler ones (CO2 , H20 &
energy).
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Carbon cycle ( Contd.)
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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
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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.)
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Nitrogen makes up about 78% of the air, but
plants cannot use N2, the stable diatomic
molecule in air.
 Plants acquire nitrogen through nitrogen
cycle.
 Nitrogen-fixing bacteria( live in roots of
legumes) and blue-green algae) are
highly organised to fix nitrogen of the
atmosphere to Ammonia ( N2 to NH3)
 They combine hydrogen of atmosphere
with Nitrogen and form Ammonia( NH3)
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The nitrogen cycle( Contd.)
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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.)
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Nitrogen enters the environment in many
ways:
Plants and animals die.
Fungi and bacteria decay dead organisms,
releasing the ammonia which is converted
back to nitrates.
Animals produce urine which is contain
nitrogenous compounds.
Denitrifying bacteria breaks 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
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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
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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
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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.
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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 oxidises
sulphur dioxide and then sulphate to the
atmosphere.
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Sulfur Cycle
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Summary:
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Food Webs
Ecological Pyramids
Biogeochemical Cycles
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