Ecosystem
communities and their abiotic environment
energy flow
passage of energy in a one way direction thru an organism
Where does energy flow start?
enters as sunlight
producers
organisms that perform photosynthesis
How much energy do producers use? From where? What happens to rest?
only 1% of energy from sun–rest reflected as heat or light
Where is energy stored in producers? Form?
chemical form–bonds of organic molecules such as glucose
organic
C bonded to C
Glucose is converted to example of what other forms within producer? Why?
ATP; used for work
What happens while work is accomplished (glucose)?
energy escapes as heat energy
food chain
energy from food passes from one organism to the next in a sequence as they’re eaten
food web
interconnected food chains in ecosystem
what does food web show?
members of each trophic level–arrows go from what’s eaten to what eats it
trophic level
eating level
Level 1: Food Web
Producers convert energy from sun into chemical energy–glucose
Level 2: Food Web
primary consumers–herbivores which eat plants and obtain the energy from the producers’ molecules
Level 3: Food Web
secondary consumers–primary carnivores which eat the herbivores, obtaining the energy stored in primary carnivores
Level 4: Food Web
tertiary consumers–secondary carnivores which eat the primary carnivores
Level 5: Food Web
Decomposers (detritivores)–obtain their energy by consuming
dead plants and animals
usually bacteria, earthworms,
Ecological pyramids
used to show the relationship between trophic levels
Pyramids can show energy, biomass, or number of organisms
Pyramid of numbers
shows the number of organisms at each trophic level
in an ecosystem–most pyramids have fewer organisms occupying each successive trophic level,
Ex of pyramid of numbers
in African grasslands, number of herbivores (zebras) is
greater than number of carnivores (lions)
Inverted pyramid of numbers
higher trophic levels have more organisms
ex of pyramid of numbers inverted
Ex- One tree (producer) provides food for thousands of insects (herbivore)
Pyramid of biomass
shows total biomass (estimate of total mass of living
material) at each successive level
Pyramid of energy-
indicates the energy content (kc/ m2/ year) of the
biomass of each level
Energy pyramids always have what sizing? Why?
Energy pyramids always have large bases and get progressively
smaller through succeeding trophic levels, because some energy is lost during each transfer and used by that organism
Ecological efficiency
describes the proportion of energy represented
at one trophic level that is transferred to the next level
What’s the usual ecological efficiency?
Usually, only 10% of the energy is transferred
cellular respiration
uses food for energy
productivity
how efficient it is with organic compounds. only measuring with producers (so really measuring how much photosynthesis is happening and how much being passed on as opposed to being used in cellular respiration)
Gross primary productivity (GPP)
rate at which energy is captured during photosynthesis by producers in a given ecosystem (or rate of organic compounds being produced)
Net primary productivity (NPP)
energy that remains in plant tissues after
cellular respiration has occurred
Find Net primary Productivity
Gross primary - Plant respiration
Productivity
What does NPP represent?
NPP represents rate at which the organic material is actually
incorporated into plant tissues to produce growth
What energy out of productivity is available to consumers?
Only energy of NPP is available for consumers
gauging primary productivity in aquatic ecosystem
Since oxygen is a product of photosynthesis, to measure the dissolved oxygen. We can then convert the amount of oxygen into mg of carbon fixed by using the calculations below.
carbon fixed
=amount of carbon that went from CO2 to carbon compounds. fixation–turning one to the other.
Calculate carbon fixed (PP)
GPP mg O2/L * .698 = mL O2 / L * .536 = mg carbon fixed/L
measuring NPP
measuring the O2 production in light bc both photosynthesis and respiration are occurring. amount of O2 found in light (after time pd)-amount of O2 found initially
measuring amount of O2 being used by respiration
by measuring the amount of O2 used in the ecosystem in the dark bc then no photosynthesis will occur.
gross productivity measurement
Here, you are taking the amount of O2 produced during net
productivity and adding the amount of oxygen lost during respiration
measuring gross productivity equation
amount of dissolved oxygen found in the light after given amount of time minus the amount of dissolved oxygen found in dark after given amount of time (bottle-dark or NPP + respiration)
measuring amount of O2 being used by respiration
amount of dissolved oxygen found initially - amount found in the dark (initial-dark)
NPP measure equation
amount of O2 found in light (after time pd)-amount of O2 found initially
(bottle-initial)
what do you need to know to measure productivity
knowing initial amount of O2 present
unit for productivity
mg O2/L
factors of productivity
Efficiency of carbon fixation o Availability of solar energy, nutrient minerals, and water o Climate factors o Human modification of the environment
Biogeochemical cycles
shows how matter moves from
one part of an ecosystem to another
Carbon cycle
movement of carbon between abiotic factors (atmosphere
and ocean) and organisms
Carbon cycle step 1
Photosynthesis in plants, algae, and cynaobacteria remove CO2 from
the atmosphere and incorporate it into
organic compounds like glucose
Carbon cycle step 2
Cellular respiration by these producers or by consumers that eat the
producers returns the CO2 to the atmosphere from the
organic compound
What have a large storage of carbon compounds?
trees, Fossil fuels such as coal, oil, and natural gases formed from the
remains of ancient organisms, limestone
Combustion
Burning–returns the carbon from trees and fossil fuels
back to the atmosphere in the form of
CO2
Limestone
sedimentary rock, is made from shells of dead marine
organisms
When is CO2 released into air or water
when rock is eroded
Nitrogen cycle
atmospheric nitrogen (78% of atmosphere) is very stable, so it must first be broken apart before organisms can use it
nitrogen fixation
Gaseous nitrogen (N2) from the atmosphere is converted into ammonia (NH3)
What performs nitrogen fixation?
nitrogen-fixing bacteria
Where do nitrogen-fixing bacteria live?
nodules of plants
cyanobacteria
fix nitrogen in aquatic environment
nitrification
convert the ammonia into nitrates- NO3-
Nitrifying bacteria
performs nitrification
assimilation
absorb NH3, NH4+, NO3-
formed and incorporate the nitrogen into
proteins, nucleic acids, and chlorophyll
When does assimilation occur?
post nitrification
When does nitrification occur?
post nitrogen fixation
Denitrifying bacteria
can convert the nitrogen compounds back into
gaseous nitrogen
denitrification
reduction
of NO3- to N2 (atmospheric nitrogen)
Phosphorous cycle
cycles from land to ocean and back to land (none in the
atmosphere)
Phosphorous cycle step 1
Water runs over rocks containing phosphorous, carrying off
inorganic phosphates
PO4(3-)
Phosphorous cycle step 2
Phosphate enters the soil where it is taken up and
used by plants
How do animals obtain phosphorus
eating the plants
what happens to phosphorus when the animal bodies containing it die
the phosphorous is released by decomposers and
reenters the soil
What happens to Dissolved phosphorous
Dissolved phosphorous enters aquatic ecosystems and is taken up by
algae and other plants, which larger organisms consume
What happens when inorganic phosphorus is released by decomposers into water?
Phosphate may be deposited on sea floor- geologic processes lift it up
where it can be eroded.
Hydrologic cycle
water circulates from the ocean to the atmosphere to the
land and back to ocean
evapo/transpiration
water evaporation from plants- adds more
water vapor to atmosphere
How does water move from atmosphere to land
Water moves from atmosphere to land and ocean as
precipitation
What happens when water evaporates from oceans, streams, rivers, lakes ?
condenses and enters the atmosphere as
clouds
runoff
when water flows from land to ocean
estuaries
areas where fresh water meets ocean
What happens when water seeps down into soil
Water also seeps down in soil to become groundwater, where it is
held- eventually supplies water to soil streams rivers plants and oceans
biomass
estimate of total mass of living
material
assimilation performed by
Roots of plants
step 3 phosphorus cycle
animals may eat the plants
step 1 nitrogen cycle
nitrogen fixation
denitrification happens when?
post assimilation or nitrification, depending on whether the plants assimilate it
Nitrogen cycle
Nitrogen fixation turns it into ammonium in soil, then it is nitrified into nitrates. It can either immediately be denitrified back to atmospheric N2, or it can be assimilated by plants and then used as amino acids and proteins in plants and animals. If so, the detritivores will decompose the organism when it dies and send to nitrogen back to soil ammonium.
