Chapter 54: Ecosystems

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Chapter 54Ecosystems

• Caroline La-Rotta, Elaina Rosario, Melissa
  Romain, and Natalie Madrowski

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Key Concepts54.1 Ecosystem ecology emphasizes
energy flow and chemical cycling.

• An ecosystem consists of all the organisms living
  in a community as well as all the abiotic factors
  with which they interact. Ecosystems are the
  transformers of energy and processors of matter.
  The principle of conservation of energy states
  that energy cannot be created or destroyed, only
  transformed. The total amount of energy in a
  process does not change. The energy comes from
  solar radiation and is released by heat from
  organisms.
• In trophic relationships, there are levels to
  which the animals are organized. The organisms
  that ultimately support all of the other
  organisms are autotrophs, also known as primary
  producers. Such organisms are photosynthetic. The
  levels above consist of heterotrophs. Primary
  consumers are herbivores that eat primary
  producers (ex plants). Secondary consumers are
  carnivores that eat herbivores. Tertiary
  consumers are carnivores that eat other
  carnivores.
• Lastly in the trophic levels, decomposers appear.
  Decomposers are consumers that obtain energy form
  nonliving organic material. The organic material
  decomposed is transferred to abiotic reservoirs,
  like soil. This way primary producers can recycle
  it into organic compounds. Decomposers are the
  magic link between consumers and producers (ex
  fungi and prokaryotes)

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54.2 Physical and chemical factors limit
primary producers in ecosystems.

• Primary production is the amount of light energy
  converted to chemical energy by autotrophs during
  a given time period. The extent of photosynthetic
  production sets the spending limit for the entire
  ecosystem. Most of the solar radiation reaches
  Earths surface and bodies of water that only
  absorb or reflect the energy. A small percentage
  of this energy actually goes to plants, and only
  some wavelengths are suitable for photosynthesis.
• Gross primary production (GPP) is the total
  primary production in an ecosystem. Not all of
  the production is stored because plants use some
  of it as fuel for cellular respiration. Net
  primary production (NPP) equals the GPP minus the
  energy used for respiration. NPP represents the
  storage of chemical energy that will be available
  to consumers in a ecosystem.
• In aquatic ecosystems, light and nutrients are
  important in controlling primary production. The
  depth of light penetration affects primary
  production throughout the photic zone of an ocean
  or lake and limited nutrients must be added in
  order for production to increase in a particular
  area.
• In terrestrial and wetland ecosystems,
  temperature and moisture are key to controlling
  primary production. Warm wet conditions promote
  plant growth. Dry and/or cold conditions lower
  productivity. There is intermediate production in
  temperate forest and grasslands because of
  moderate climates. Actual evapotranspiration is
  the actual amount of water transpired by plants
  and evaporated from landscape. It increase with
  the amount of precipitation in a region and the
  amount of solar energy available to drive
  evaporation and transpiration.

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54.3 Energy transfer between trophic levels is
usually lass then 20 efficient.

• Secondary production is the amount of chemical
  energy in consumers food that is converted to
  their own biomass during a given time period. Net
  secondary production is the energy stored in
  biomass that is represented by growth and
  reproduction.
• Production efficiency is the fraction of energy
  stored in food that is not used for respiration.
  Trophic efficiency is the percentage of
  production transferred from one trophic level to
  the next. Usually, trophic efficiency is less
  than production efficiency because it takes into
  account the energy lost through respiration,
  energy contained in feces, energy in organic
  material in a lower trophic level that is not
  consumed by the next trophic level.
• Pyramids of net production shows the loss of
  energy with each transfer in a food chain.
  Pyramids of numbers show the number of individual
  organisms present in a trophic level. Pyramids of
  biomass represent the standing crop in one
  trophic level.
• The Green World Hypothesis states that
  terrestrial herbivores will consume relatively
  little plant biomass because they are held in
  check by a number of factors. Some examples are
  predation, parasitism, and disease.

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54.4 Biological and geochemical processes move
nutrients between organic and inorganic parts of
the ecosystem.

• The general model of the chemical cycling rout
  varies with the particular element and the
  trophic structure. Two categories of
  biogeochemical cycles are global and local.
  Global gaseous forms of carbon, oxygen, sulfur,
  nitrogen and local forms of phosphorus,
  potassium, and calcium soils the main abiotic
  reservoir. Each reservoir is defined by tow
  characteristics whether it contains organic or
  inorganic materials and whether or not the
  materials are directly available for use by
  organisms.
• The following four things are important factors
  ecologists consider as they research
  biogeochemical cycle 1.) The biological
  importance of each chemical. 2.) The forms in
  which each chemical is available or used by
  organisms. 3.) The major repositories or
  reservoirs for each chemical. 4.) The key
  processes that drive the movement of each
  chemical through its biogeochemical cycle. The
  temperature and the availability of water affects
  rates of decomposition and nutrient cycle times.
• Herbert Bormann had lead a group of scientists in
  studying nutrients cycling since 1963.
  Preliminary studies confirmed that internal
  cycling within a terrestrial ecosystem conserves
  most of the mineral nutrients. The amount o
  nutrients leaving an intact forest ecosystem is
  controlled mainly by plants.

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54.5 The human population is disrupting
chemical cycles throughout the biosphere.

• Human activity such as removing nutrients from
  one part of the biosphere and adding the to
  another toxic materials into the ecosystems often
  intrudes in nutrients cycles. Humans also impact
  the biospheres chemical dynamics by agriculture
  and nitrogen cycling. Consideration amounts of
  the nutrients in fertilizer pollute groundwater
  and surface water aquatic ecosystems, where
  they can stimulate excess algal growth.
• The burning of wood, coal, and other fossil fuels
  releases oxides of sulfur and nitrogen that react
  with water in atmosphere, forming sulfuric and
  nitric acid. Acid precipitation can damage
  plants, directly, mainly by leaching nutrients
  from leaves. One of the reason such toxics are
  particularly harmful is that they become more
  concentrated in successive trophic levels of a
  food web biological magnification. It occurs
  because the biomass at any given trophic level is
  produced from a much larger biomass ingested from
  the level below. Top level carnivores tend to
  be the organism most affected by toxic compounds
  such as DDT, in the environment.
• Because of the burning of wood stand fossil fuels
  and other human activities, atmospheric
  concentration of CO2 has been steadily
  increasing. The ultimate effects may include
  significant warming and other climate changes.
  The ozone layer absorbs UV radiation, preventing
  much of it from reaching organisms in the
  biosphere. Human activities including release of
  chlorine containing pollutants are eroding the
  ozone layer, with dangerous results.

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Concepts that can be effected by DDT.

• Trophic relationships Tropic relationships are
  the arrangement of organisms from primary
  producers to tertiary consumers. If DDT was used
  on plants, it would destroy insects. Eventually,
  the plants will get infected. With the infection
  there will be a train reaction throughout the
  trophic levels. The plants will be infected, then
  it will transfer to the primary consumers and so
  on, until it reaches the last consumer in the
  food chain. Soon enough some organisms will die
  from the pesticide.
• Marine and Freshwater Ecosystems Such ecosystems
  are bodies of water. If DDT was used on the
  plants, eventually the water would get infected.
  The pesticide is applied to the plants, which
  will touch the soil. DDT now becomes apart of the
  soil. The soil will then run off into the bodies
  of water, contaminating them with DDT. The spread
  of DDT in the water ecosystems will eventually
  infect all of the organisms that live in it, like
  fish.
• Terrestrial and wetland ecosystems In some case,
  DDT is sprayed onto plants from above, by an
  airplane that flies across it. In this form the
  DDT will not only be applied to small plants but
  also to trees. Ecosystems with abundance of trees
  are either terrestrial or wetland ecosystems. By
  applying the pesticide from the air, all of the
  organisms below will be infected. Eventually all
  of the organisms will die from the harmful
  pesticide.

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Environmental Stresses effect concepts

• Green World Hypothesis This hypothesis states
  that there will be a decrease in food. Due to the
  lessening of food, people will eventually be
  guided to sickness and after serious sickness
  death. As the plant and green life decreases, the
  herbivore population will decrease and then the
  carnivore will do the same. Eventually this chain
  will reach the human population.
• Acid Rain Acid precipitation is a major problem
  effecting water ecosystems. Acid rain is a type
  of pollution in the form of water. It falls onto
  our lands and into our waters, which make up most
  of the land. Acid rain pollutes the oceans,
  river, lakes ,and other bodies of water. As the
  water is polluted the fish and other marine life
  get poisoned and eventually die. As a final
  result, marine life will be lost.
• Global Warming Global warming, a serious problem
  all over the world, will eventually affect our
  terrestrial and wetland ecosystems. The wetlands
  will get dried up so much that here will be no
  water left and organisms can not survive.
  Terrestrial lands will have its plants, trees,
  and other useful resources destroyed eventually
  eliminating living organisms.