Ecosystem and Material Cycle : Ch' 5

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• Chapter 4, 5, and 6
• Ecosystem and Material Cycle Ch. 5
• Biomes and Habitat Ch. 4
• Ecological Succession Ch. 5
• Population Dynamics Ch. 6
• Biodiversity Ch. 6

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Components of Ecosystems
Ecosystems are ecological units that include all
the living or biotic factors and non-living or
abiotic factors in an area.
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Abiotic factors determine the type of organisms
that can successfully live in a particular area.
Some of the major nonliving include regions such
as ponds, caves, or portions of a forest or
desert.

• Biotic factors include the plants, animals,
  fungi, bacteria and any other living things that
  live in an area. Categories include
• Producers or autotrophs make their own food.
  Producers, such as plants, make food through a
  process called photosynthesis. In photosynthesis,
  plants use carbon dioxide and water to make
  sugar. This food is used by the plant for its own
  energy or may be eaten by consumers.
• Consumers or heterotrophs need to eat food that
  autotrophs have produced. There are different
  types of consumers. Herbivores eat plants.
  Carnivores eat animals. Omnivores eat both plants
  and animals.
• Decomposers are heterotrophs that break down
  dead tissue and waste products. They play a very
  important role in the ecosystem because they
  recycle nutrients. Bacteria and fungi are
  decomposers.

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Biogeochemical cycling

• Biogeochemical cycles The transport and
  transformation of substances in the environment,
  through life, air, sea, land, and ice. Include
  the circulation of certain elements, or
  nutrients, upon which life and the earth's
  climate depend.
• Cycle continuously from the nonliving environment
  to living organisms (biota) and then back again
• Nutrientatom, ion, or molecule an organism needs
  to live, grow, or reproduce.

• Carbon cyclebasic building block of organic
  compounds necessary for life
• Nitrogen cycleused to make vital organic
  compounds such as amino acids, proteins, DNA,
  RNA
• Phosphorus cyclenecessary for nucleic acids,
  cell membranes, energy-transfer reactions, bones,
  and teeth and is often the limiting factor for
  plant growth on land unless phosphorus is applied
  to the soil as fertilizer.
• Sulfur cycleimportant for proteins

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• Carbon cycle
• Producers remove CO2 from atmosphere water
  use photosynthesis to convert CO2 to
  carbohydrates
• Oxygen consuming producers, consumers, and
  decomposers carry out aerobic respiration
  breaking glucose back to CO2 for reuse by
  producers
• Over millions of years buried deposits of dead
  plant matter bacteria are compressed between
  layers of sediment where they form carbon
  containing fossil fuels
• Carbon is not released to the atmosphere as CO2
  for recycling until they are extracted and burned
• Human Impacts on Carbon Cycle
• Clearing trees other plants that absorb CO2
  through photosynthesis
• Adding large amounts of CO2 by burning fossil
  fuels and wood

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Nitrogen cycle

• Fixationspecialized bacteria convert gaseous
  nitrogen to ammonia (NH3) that can be used by
  plants Performed by cyanobacteria Rhizobium
  bacteria living within small nodules on the root
  systems of many species, including legumes
• Nitrificationtwo step process that converts
  ammonia to nitrite ions (NO2-)and then to
  nitrates(NO3-) which are easily absorbed by
  plants as nutrients Performed by aerobic
  bacteria
• Assimilationplant roots absorb inorganic
  ammonia, ammonium ions, and nitrate ions formed
  by nitrogen fixation and nitrification Ions are
  used to make nitrogen-containing organic
  molecules
• Ammonification decomposer bacteria convert
  nitrogen-rich organic compounds, wastes, cast-off
  particles, and dead bodies into simpler nitrogen
  containing inorganic compounds and water soluble
  salts containing ammonium ions
• Denitrificationother specialized bacteria
  (anaerobic living in waterlogged soils or in
  bogs, lakes, swamps) convert ammonia and
  ammonium ions back into nitrite and nitrate and
  then into nitrogen gas.

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• Human Impacts on Nitrogen Cycle
• Adding large amounts of Nitric oxide (NO) into
  the atmosphere when fuels are burned NO O2
  forms NO2 NO2 H2O forms HNO3 which leads to
  acid rain
• - Can damage weaken trees
• - Upset aquatic ecosystems
• - Corrode metals
• - Damage marble, stone, other building
  materials
• Adding nitrous oxide(N2O) to the atmosphere
  through the action of anaerobic bacteria in
  livestock wastes commercial fertilizers
• Removing nitrogen from topsoils when
  nitrogen-rich crops are harvested and when
  irrigation is used
• Adding nitrogen compounds to aquatic ecosystems
  in agricultural runoff and discharge of municipal
  sewage Leads to eutrophication (rapid growth of
  algae)
• - Subsequent breakdown of algae can deplete water
  of DO(dissolved oxygen) and disrupt aquatic
  ecosystems by killing some fish

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Phosphorus Cycle

• Phosphorus moves slowly from phosphate deposits
  on land and in shallow ocean sediments to living
  organisms and then slowly back to land ocean
• Typically found as phosphate salts containing
  phosphate ions in terrestrial rock formations and
  ocean bottom sediments

• Human Impacts on Phosphorus Cycle
• Mining large quantities of phosphate rocks for
  use in commercial inorganic fertilizers
  detergents
• Reducing the available phosphate in tropical
  forests by removing trees
• Adding excess phosphate to aquatic ecosystems in
  runoff of animal wastes from livestock feeding
  lots, runoff of commercial phosphate fertilizers,
  discharge of municipal sewage

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Sulfur Cycle

• Much sulfur is stored underground in rocks and
  minerals containing sulfate salts buried deep
  under ocean sediments Sulfur enters atmosphere
  from natural sources
• Hydrogen sulfide is released from active
  volcanoes by the breakdown of organic matter in
  swamps, bogs, tidal flats caused by decomposers
  that do not use oxygen
• Certain marine algae produce large amounts of
  volatile dimethyl sulfide (DMS) Serve as
  nuclei for the condensation of water into
  droplets and changes in DMS emissions can affect
  cloud cover and thus climate
• Human Impacts on Sulfur cycle
• Burning sulfur containing coal and oil to
  produce electric power
• Refining petroleum
• Using smelting to convert sulfur compounds of
  metallic minerals into free metals such as
  copper, lead, and zinc

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Habitat
All living things have a habitat or the physical
area in which they live. The habitat of an
organism may include many different areas

• Aquatic Ecosystems
• Freshwater and saline
• Estuaries and wetlands
• Shorelines

• Terrestrial Biomes
• Deserts
• Grassland
• Tundra
• Conifer Forest
• Deciduous Forest
• Tropical Forest

Habitat destruction some organisms may become
threatened, endangered and eventually extinct.
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Desert

• Lack of moisture means cant store heat
  -Temperature fluctuations
• Need 2-4 in. of annual precipitation to support
  species rich community - Adapted shrubs, small
  trees, animals, insects
• Fragile ecosystems (soils very thin)

Grassland and Savannas

• Inadequate precipitation for (many) trees - Grass
  fires kill tree seedlings
• Rich communities and rich soils
• Herds!

Tundra

• Climate too brutal for trees - Short growing
  season, Frost year round, and Plenty of
  unavailable water
• Arctic - Main deterrent to plant growth is
  permafrost
• Alpine - Deterrents are UV radiation, temperature
  swings, thin soil

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Conifer Forest

• Northern (Boreal) - Moisture limited, Temperature
  tolerant, and Acidic soil
• Temperate
• Sandy soil, frequent fires OR
• Mild temperatures, abundant precipitation

Deciduous Forest

• Adapted to good growing season followed by winter

Tropical Forest

• Lots of precipitation!
• Incredible species richness
• 90 of nutrients stored in Ecosystem, little in
  soil

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Communities in Transition

• Ecological Succession Transition from one
  biotic community to another
• Populations of existing species are taking
  advantage of a new area as conditions become
  favorable.
• It is not a matter of new species developing, or
  even old species adapting, to new conditions.
• Succession does not go on indefinitely. A stage
  is reached in dynamic balance with one another
  and with the physical environment.
• In any climax ecosystem there are other,
  earlier, stages of succession present. Without
  the presence of these earlier stages, species
  would be lost and ecosystems could not recover
  from disturbances.

Primary succession The initial invasion and
progression from one biotic community to the next
if an area has not been occupied by organisms
previously - Soil and soil organisms do not exist
prior to the beginning of this successional
process. Secondary succession The invasion and
progression from one biotic community to the next
if an area has been previously occupied by
organisms and something has occurred to leave
only the bare soil - Soil and soil organisms
exist prior to the beginning of this successional
process.
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Population Dynamics

• Population all the members of a given species
  in a given area
• Biotic Potential reproductive rate
• Environmental Resistance biotic and abiotic
  factors limiting population size
• Recruitment  the ability to survive environment
  resistance factors and become part of the
  breeding population.
• Replacement level when recruitment is just
  enough to replace the adults.
• Reproductive Strategies
• High biotic potential and low recruitment 
  bacteria, flies, rabbits
• Low biotic potential and high recruitment 
  humans, elephants, primates

• Growth Curve how biotic potential and
  environmental resistance combine to cause a
  population to grow or decline.
• J-curve before environmental resistance factors
  kick in to reduce population size
• S- curve a balance between environmental
  resistance and biotic potential
• Population equilibrium deaths equal births

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Carrying Capacity -The maximum population of an
organism that a given habitat will support
without the habitat being degraded over the long
term. This is the upper limit on the size of a
population.
Density-dependent factors and Density-independent
factors

• Density-dependent factors The impact of some
  environmental factors dependent on the density of
  the population, which will have impact on
  continued population growth.
• - Food is a density dependent factor the more
  individuals competing for the same food source,
  the more difficult it is to get food.
• Density-independent factors The impact of some
  environmental factors not dependent on the
  density of the population.
• Include an unusual heat wave or hard freeze.
• If a particular limiting factor moves outside an
  organism's range of tolerance, then the organism
  dies irrespective of how many there might be in
  the population.
• A spill of pesticides into a river (as happened
  on the upper Sacramento River in the early 1990s
  because of a train accident) resulted in the
  sudden death of the river ecosystem that was not
  related to the population size of any species.

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Critical Numbers
Critical Number The minimum number of organisms
necessary for a species to survive. - If the
number of organisms drops below the critical
number, extinction is almost certain. - As a
population nears its critical number density 
independent factors become very important. A
single fire, hurricane, toxic chemical spill,
housing development, or logging operation could
eliminate the species. - The most difficult
aspect of this concept is that we do not know the
critical number for most species. To determine
the critical number for a species we must need to
know its biotic potential, all its environmental
resistance factors, the range of possible values
for each of the factors, the possible
interactions among the factors, etc.
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Ecosystem Disturbance

• Disturbances
• - provide habitat for a wide array of species. In
  any area, all stages of succession are likely to
  be represented because of large and small
  disturbances.
• - can be a problem when a species is close to its
  critical number. If humans have caused a
  population to decrease close to its critical
  number and a density independent disturbance
  event occurs, then a species can become extinct.
• Fire
• - A necessary factor for diverse number of
  species
• - Certain species e.g., the fire pines, are
  dependent on fire. Without fire their cones do
  not open, and the bare ground necessary for seed
  germination does not exist.
• - Other species are adapted to fire conditions.
  Manzanita will sprout rapidly after a fire as
  long as its extensive root system has not been
  damaged. The wetter portions of the Great Plains
  were dependent on fire to maintain the
  grasslands.
• - Fire helps maintain a balance among species (in
  a forest, fire favors pines, lack of fire favors
  broadleaf trees) or may release nutrients that
  have not decomposed because of arid conditions.
• - Creates pockets of secondary succession.

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Competition between Plant Species 1. Habitats
and niches reduce the competition between plants.
Different combinations of soil types, moisture,
temperature, light, etc., produce different
habitats and niches. Plants (and other organisms)
have adapted to different biotic and abiotic
requirements. 2. Competition between plants is
limited when plants release chemicals to inhibit
the growth of other plants, when grazers reduce
the population of plants, when parasites,
viruses, and other plant pathogens reduce the
vigor, reproductive capacity, or life span of
plants. 3. Mutualism reduces competition.
Epiphytes live on the branches of trees and the
epiphyte is thought to provide nutrients captured
by rainfall to the trees. 1. Herbivores consume
plants and therefore keep the size of a plant
population in check. (This is one of the
mechanisms in plant competition.) If there are
too many herbivores, the herbivores can consume
the plants faster than the plants can reproduce.
This is called overgrazing. 2. "For
sustainability, the size of consumer populations
is controlled so that overgrazing or overuse does
not occur"  the basic principle of ecosystem
sustainability.
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Predator-Prey and Host-Parasite Dynamics 1. The
interaction between predator and prey and host
and parasite keeps both populations in balance.
As the population size of the prey or host
increases, the population size of the predator or
parasite increases because there is more food. As
the predator or parasite population increases,
the number of prey or hosts declines because the
predator or parasite has eaten them. 2. The
reintroduction of wolves to Yellowstone had
results that nobody anticipated. Changes included
increased riparian habitat plant diversity (elk,
to protect themselves from wolves, spend less
time along rivers and more time in the trees),
increased song bird numbers and type (elk no
longer trample riparian plants, and bird habitats
have returned), and increased raptor numbers
(wolves have decreased coyote population, causing
an increase in the rodent population, which has
provided raptors with more food).
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• Biodiversity
• Species diversityvariety of different species
• Genetic diversitygenetic variability among
  individuals within each species
• Ecological diversityvariety of ecosystems
• Functional diversityfunctions such as energy
  flow and matter cycling needed for the survival
  of species and biological communities

• Human Impacts on biodiversity
• Disturbed or degraded 40-50 of earths land
  surface
• Use, destroy, or waste 40 of all terrestrial
  net primary productivity
• According to WWF, 34 of fish species, 25 of
  amphibians, 24 of mammals, 20 of reptiles, 14
  of plants, and 12 of birds are under threat of
  extinction
• 95-98 of all virgin forests in US have been
  destroyed since 1620
• Difficulties in determining impact on
  biodiversity
• Number of species are unknown (best guess is
  12-14 million)
• Only 1.4-1.8 million species have been named
• Estimates of extinction are based on inadequate
  data and sampling

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• Factors that increase biodiversity
• Physically diverse habitat
• Moderate environmental disturbance
• Small variations in environmental conditions
  (nutrient supply, precipitation, temperature)
• Middle stages of succession
• Evolution
• Factors that decrease biodiversity
• Environmental stress
• Large environmental disturbance
• Extreme environmental conditions
• Severe limitation of essential nutrients,
  habitat, or other resource
• Introduction of alien species
• Geographic isolation

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Causes of Species Extinction

• Habitat Disturbance Tropical deforestation is
  greatest eliminator of species followed by
  destruction of coral reefs wetlands
• Nonnative species Many introduced species have
  no natural predators, competitors, or pathogens
  to control numbers
• Commercial hunting poaching
• Predators Pest Control African farmers kill
  elephants that trample their food crops
• Loss of Genetic Diversity Limits ability to
  survive by reducing ability to reproduce and
  adapt to changing conditions

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• Solutions to Protecting Wild Species
• Bioinformaticsapplied science of managing,
  analyzing, and communicating biological
  information
• International treaties
• Convention on International Trade in Endangered
  Species (CITES)1975
• Convention on Biological Diversity (CBD)1992
  Legally binds signing nations to reverse the
  global decline in biodiversity
• Zoos Game parks Collecting wild eggs laid by
  critically endangered species and hatching them
  in zoos or research centers
• Wildlife Management Manipulating wildlife
  populations and their habitats for their welfare
  for human benefit