Transcript Chapter 57 - Workforce3One

Chapter 57
Dynamics of ecosystems
What are Biogeochemical Cycles?
• Earth has fixed number of each type of atoms of
biological importance –recycled via biogeochemical
cycles
• Biogeochemical cycles- The atoms of various
chemical elements move through ecosystems –
involve biological organisms and processes +
geological (abiotic) systems and processes.
• Biogeochemical cycles includes processes that occur
on many spatial (cellular to planetary) and multiple
timescales from seconds (biochemical reactions) to
millennia (weathering of rocks)
Carbon cycle
• Figure 57.1-Photosynthesis by plants and algae
capture carbon in form of organic chemical
compounds (Co2 and HCO3-)
• Cellular respiration and combustion of fuels
return carbon to atmosphere (Co2 or HCO3-)
• Microbial methanogens (live in bottom of
water) – produce CH3 ---enter into atmosphere
as Co2.
• Decaying organisms also produce Co2
The water cycle-figure 57.2
• Water is a compound – Synthesized during cellular
respiration and broken during photosynthesis
• Enters atmosphere via evaporation (water resources
and plant) and transpiration (plant) and returns to
earth’s surface as precipitation
• Groundwater (available in oceans, lakes etc)
• Underground layers of rocks, sand and gravel
saturated with water – aquifers
• Aquifers are used and contaminated by humans
The Nitrogen cycle (figure 57.4)
• Plants and animals cannot use nitrogen (elemental
form) directly from atmosphere
• Nitrogen fixation- Synthesis of NH3 from N2
• Nitrification- Synthesis of NO3- from NH3
• Plants and algae utilize NH3 and NO3• Denitrification - some prokaryotes return back NH3
and NO3- as N2 to atmosphere
• Human and mammal excreta – Urea---converted to
NH3---- used by plants and algae
• Fertilizer application of N2- doubled the rate of
N2 transfer
Phosphorous cycle (figure 57.5)
• Phosphorous has no gaseous form – do not cycle through the
atmosphere
• Available in ecosystem – inorganic phosphate (PO4-)
• Released by weathering of rocks and it flows into oceans
where it is deposited in deep-sea sediments
• Plant and algae use PO4- present in soil or water
• Animals tap PO4- from plants and algae
• Remineralization- Decaying microbes break up organic
compounds in bodies of dead organisms- release as inorganic
PO4- plants and algae can reuse it
• Application of phosphorous fertilizers to soils
Energy flows through trophic levels
• Organic compounds are synthesized by
autotrophs – photoautotrophs and
chemoautotrophs – and utilized by
heterotrophs
• Energy passes from organism to organism,
each feeding level is called a trophic level,
and sequence through progressive trophic
levels – Food chain (figure 57.8)
Trophic levels
• Primary producers-Herbivores-Primary
carnivores-secondary carnivores-Detritivores
• Detritivores feed on dead matter of all other
tropic levels
• Detrius – dead organic matter
• Decomposers – subcategory of detritivores
Productivity
• Productivity of atrophic level is the rate at which the
organisms in trophic level are collectively synthesizing new
organic matter
• Primary productivity of autotrophs can be expressed as
Gross primary productivity (GPP) and Net primary
productivity (NPP)
• GPP – the rate at which the primary producers synthesize new
organic matter
• NPP= GPP - respiration of primary producers
• Productivity of a heterotroph tropic level – secondary
productivity
How trophic levels process energy?
• 1% of solar energy is captured for photosynthetic
processes.
• Most of the chemical bond energy ingested (figure
57.9 and 57.10) is lost in feces
• Some of the ingested energy is lost in fuelling
respiration
• Only some amount of ingested energy is used by the
animal (heterotroph or autotroph)
• In general, only about 10% of the energy of one
trophic level is available to the next trophic level
Ecological pyramids
• Ecological pyramids of energy flow, biomass
or numbers are upright.
• Happens when one trophic level has greater
biomass or more number of organisms than
trophic level below it (figure 57.13)
What are Trophic-Level Interactions
• Changes in species at any one trophic level may have
multiple effects on other trophic levels
• A trophic-cascade occurs when effects exerted at an
upper trophic level affect a lower level
• Top-down trophic effect occurs when changes in top
trophic level affect primary producers
• Bottom-up effect occurs when changes in primary
productivity affects higher trophic levels
• Species richness affect community stability –
community’s composition and ability to resist
disturbance
Island Biogeography
• Species area relationship can be explained by
colonization and extinction of species
(populating a geographic area or isolating)
• Smaller islands have fewer species than
large islands because of higher rates of
extinction
• Near islands have more species than far
islands because of higher rates of
colonization
This project is funded by a grant awarded under the President’s Community Based Job Training Grant as implemented by the U.S. Department
of Labor’s Employment and Training Administration (CB-15-162-06-60). NCC is an equal opportunity employer and does not discriminate on
the following basis:
against any individual in the United States, on the basis of race, color, religion, sex, national origin, age disability, political affiliation or belief; and
against any beneficiary of programs financially assisted under Title I of the Workforce Investment Act of 1998 (WIA), on the basis of the
beneficiary’s citizenship/status as a lawfully admitted immigrant authorized to work in the United States, or his or her participation in any WIA
Title I-financially assisted program or activity.
“This workforce solution was funded by a grant awarded under the President’s
Community-Based Job Training Grants as implemented by the U.S.
Department of Labor’s Employment and Training Administration. The solution
was created by the grantee and does not necessarily reflect the official position
of the U.S. Department of Labor. The Department of Labor makes no
guarantees, warranties, or assurances of any kind, express or implied, with
respect to such information, including any information on linked sites and
including, but not limited to, accuracy of the information or its completeness,
timeliness, usefulness, adequacy, continued availability, or ownership. This
solution is copyrighted by the institution that created it. Internal use by an
organization and/or personal use by an individual for non-commercial purposes
is permissible. All other uses require the prior authorization of the copyright
owner.”