Nutrient Cycles or

1
Chapter 4

• Nutrient Cycles or
• Biogeochemical Cycles

2
Type of Nutrients

• Nutrient Any atom ion, or molecule an organism
  needs to live grow or reproduce
• Ex carbon, oxygen, hydrogen, nitrogen etc
• Macronutrient nutrient that organisms need in
  large amount
• Ex phosphorus, sulfur, calcium, iron etc
• Micronutrient nutrient that organism need in
  small amount
• Ex zinc, sodium, copper etc

3
Matter Cycling in Ecosystems

• Nutrient cycles or Biogeochemical cycles, involve
  natural processes that recycle nutrients in
  various chemical forms in a cyclic manner from
  the nonliving environment to living organisms and
  back to non living environment again.

4
Major Types of Nutrient Cycles

• Hydrologic
• Water in the form of ice, liquid water, and water
  vapor cycles
• Operates local, regional, and global levels
• Atmospheric
• Large portion of a given element (i.e. Nitrogen
  gas) exists in gaseous form in the atmosphere
• Operates local, regional, and global levels
• Sedimentary
• The element does not have a gaseous phase or its
  gaseous compounds dont make up a significant
  portion of its supply
• Operates local and regional basis

5
Nutrient Cycling Ecosystem Sustainability

• Self Contained
• Energy flow and nutrient cycling seem to imply
  that ecosystems are virtually self-sustaining,
  closed systems, at the ecosphere level
• As long as they are not disturbed by human
  activates such as clearing
• Forest clearing can cause loss of nutrient
• Nutrients lost form one ecosystem must enter one
  or more other ecosystems

6
Nutrient Cycling Ecosystem Sustainability

• Nutrient Cycling and Sustainability
• Given time natural ecosystems tend to come into a
  balance, wherein nutrients are recycled with
  reasonable efficiency
• Humans are accelerating rates of the flow of
  mater, causing nutrient loss from soils
• Scientist warn that this doubling of normal flow
  of nitrogen in the nitrogen cycle is a serious
  global problem that contributes to global
  warming, ozone depletion, air pollution, and loss
  of biodiversity
• Isolated ecosystems are being influenced by human
  actives

7
Human Impacts to cycles
8
Impact

• Fertilizers with NO3- added to the soil in large
  quantities are speeding up the N cycle.
• Burning fossil fuels adds NO to the air, becomes
  HNO3 (acid rain)

9
Human Impacts to cycles

• SO2 sulfur dioxide from cars and industry
  becomes H2SO4 in the atmosphere, leads to acid
  rain

10
Human Impacts to cycles

• Fertilizers added to the soil speed up the
  phosphorous cycle
• Removing plants from the rain forest, decreases
  available P.

11
Limiting Factor Principle

• Too much or too little of any abiotic factor can
  limit growth of population, even if all the other
  factors are at optimum (favorable) range of
  tolerance.
• Ex If a farmer plants corn in phosphorus-poor
  soil, even if water, nitrogen are in a optimum
  levels, corn will stop growing, after it uses up
  available phosphorus.

12
Chapter 4

• Ecosystem Components

13
Living Organisms in Ecosystem

• Producers or autotrophs- makes their own food
  from compounds obtained from environment.
• Photosynthetic producers- convert sunlight,
  abiotic nutrients to sugars and other complex
  organic compounds.
• Chemosynthetic producers use simple inorganic
  compounds (ex. H2SO4)

14
Consumers or Heterotrophs

• Obtain energy and nutrient by feeding on other
  organisms or their remains

15

• 3. Herbivores (plant-eaters) or primary
  consumers- they feed directly on producers
• Deer, goats, rabbits
• 4. Carnivores (meat eater) or secondary
  consumers-feed only on primary consumer
• Lion, Tiger
• 5. Tertiary (higher-level) consumer- feed only on
  other carnivores
• Wolf
• 6. Omnivores- consumers that eat both plants and
  animals
• Ex pigs, humans, bears

16

• 7. Scavengers- feed on dead organisms
• Vultures, flies, crows, shark
• 8. Decomposers- Fungi and bacteria that breaks
  down and recycles organic materials from wastes
  of all organisms. Dead organisms waste to
  nutrients
• 9. Detritivores- live off detritus
• Detritus parts of dead organisms and wastes of
  living organisms.
• In nature waste becomes food source
• Biodegradable- can be broken down by decomposers

17
Second Law of Energy

• Organisms need high quality chemical energy to
  move, grow and reproduce, and this energy is
  converted into low-quality heat that flows into
  environment
• Trophic levels or feeding levels
• Producer is a first trophic level
• primary consumer is second trophic level
• secondary consumer is third
• Decomposers process detritus from all trophic
  levels.

18

• Food web-complex network of interconnected food
  chains.
• Food web and chains are one-way flow of energy
  and cycling of nutrients through ecosystem.

19
Food Webs

• Grazing food webs energy and nutrients move from
  plants to herbivores, then through an array of
  carnivores, and eventually to decomposers
• Detrital food webs organic waste material or
  detritus is the major food source, and energy
  flows mainly from producers (plants) to
  decomposers and detritivores.

20
Biomass

• Dry weight of all organic matter contained in
  organisms.
• Biomass is measured in dry weight because water
  is not a nutrient or a source of energy
• Ex biomass of first trophic levels are dry mass
  of all producers
• On successive trophic level, biomass is neither
  eaten, digested, nor absorbed it simple goes
  through the intestinal tract of consumer and is
  expelled as fecal waste.
• Useable energy transferred as biomass varies from
  5-20

21

• Pyramid of Energy Flow
• More steps or trophic levels in food chain or
  web, greater loss of usable energy as energy
  flows through trophic levels
• More trophic levels the Chains or Webs have more
  energy is consumed after each one. Thats why
  food chains and webs rarely have more than 4
  steps
• Pyramid of biomass- storage of biomass at various
  trophic levels of ecosystem
• NOTE After every trophic level less and less
  energy is transferred
• Producer gets the most amount of energy, thats
  why there is a lot of producers, herbivores
  consume producers however they need to consume
  they get less energy then producers by consuming
  them
• Carnivores get much less energy than herbivores,
  thats why there are more herbivores than
  carnivores, and carnivores

22
Ecological Efficiency

• Percentage of energy transferred from one trophic
  level to another.
• 10 ecological efficiency
• green plants transfer 10,000 units of energy from
  sun
• only about 1000 energy will be available for
  herbivores
• 100 units for primary consumer
• 10 units for secondary consumer

23
Ways to unravel workings of ecosystem

• Field research- going into nature and observing
  ecosystem
• Laboratory research- observe and making
  measurements under laboratory condition
• System analysis- view ecosystem and study their
  structure and functions (1960s)

24
FIELD RESEARCH

• Going into nature and observing/measuring the
  structure of ecosystems
• Majority of what we know now comes from this type
• Disadvantage is that it is expensive,
  time-consuming, and difficult to carry out
  experiments due to many variables

25
LABORATORY RESEARCH

• Set up, observation, and measurement of model
  ecosystems under laboratory conditions
• Conditions can easily be controlled and are quick
  and cheap
• Disadvantage is that it is never certain whether
  or not result in a laboratory will be the same as
  a result in a complex, natural ecosystem

26
SYSTEMS ANALYSIS

• Simulation of ecosystem rather than study real
  ecosystem
• Helps understand large and very complicated
  systems

27
Why Is Biodiversity So Important?

• Biodiversity is the variety of different species,
  genetic variability among individuals within each
  species, and variety of ecosystems
• Gives us food, wood, fibers, energy, raw
  materials, industrial chemicals, medicines, and
  provides for billions of dollars in the global
  economy
• Provides recycling, purification, and natural
  pest control
• Represents the millions of years of adaptation,
  and is raw material for future adaptations