Principles of Ecology: Matter, Energy, and Life

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Principles of EcologyMatter, 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 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

• Photosynthesis
• 6H2O 6CO2 sun ? C6H12O6 (sugar) 6O2
• Cellular Respiration
• C6H12O66O2 ? 6H2O 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 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

• 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 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

• 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.
• 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 energyfood chain

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Trophic Levels
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Ecological Pyramids

• 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 himhe does not eat the
  flesh completely..energy is lost in the
  ecosystem.

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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 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.)

• 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 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.)

• 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 chain made up of several
  amino acids)

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Nitogen cycle (cont.)

• 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

• 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 oxidises
  sulphur dioxide and then sulphate to the
  atmosphere.

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Sulfur Cycle
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Summary

• Food Webs
• Ecological Pyramids
• Biogeochemical Cycles

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