ch. 55 Flashcards
ecosystem
consists of all organisms living in an area as well as the abiotic factors with which they interact
2 main processes for dynamics of ecosystem
- energy flow
- chemical cycling
what do ecologists study
transformations of energy and matter in an ecosystem and map the movements of chemical elements
first law of thermodynamics
energy cannot be created or destroyed, only transferred or transformed
how does energy enter and leave an ecosystem
- enters as solar radiation
- conserved
- lost from organisms as heat
second law of thermodynamics
every exchange or energy increases entropy of the universe
where is some energy lost in energy conversions
heat
law of conservation of mass
matter cannot be created or destroyed
chemical elements are ____________ ____________ within ecosystems
continually recycled
open systems
absorb energy and mass and release heat and waste products
what happens if a nutrient’s outputs from an ecosystem exceed its inputs
the nutrient will limit production
autotrophs
build molecules themselves using photosynthesis or chemosynthesis as an energy source to connect carbon together
heterotrophs
depend on biosynthetic output of other organisms
where do energy and nutrients pass
- primary producers (autotrophs)
- primary consumers (herbivores)
- secondary consumers (carnivores)
- tertiary consumers (carnivores that feed on other carnivores)
detritivores/decomposers
heterotrophs that derive their energy from detritus
detritus
nonliving organic matter
main detritivores
prokaryotes and fungi
what connects all trophic levels
decomposition
primary production
amount of light energy converted to chemical bond energy by autotrophs during a given time period
gross primary production (GPP)
total primary production
how is GPP measured
conversion of energy from light (or chemicals) to the chemical bond energy of organic molecules per unit time
net primary production (NPP)
GPP - Ra
- Ra = energy used by autotrophs for respiration
- amount of new biomass added in a given time period
on average, NPP is ________ GPP
one-half
how is primary production expressed
- energy per unit area per unit time
- bio mass added per unit area per unit time
only what is available to consumers
NPP
most productive ecosystems per unit area
- tropical rain forests
- estuaries
- coral reefs
why do marine ecosystems contribute much to global net primary production if they are unproductive
because of their size
what limits primary production in marine/freshwater ecosystems
light and nutrients
what affect primary production in the photic zone of oceans/lakes
depth of light penetration
limiting nutrient
element that must be added for production to increase in an area
nutrients that most often limit marine production
nitrogen and phosphorus
what does the upwelling of nutrient-rich waters in parts of oceans contribute to
regions of high primary production
what causes eutrophication of lakes
sewage runoff
eutrophication of lakes
- nutrient inputs from sewage promote growth of primary producers
- detritivores use up dissolved oxygen, breaking down dead producers
- loss of oxygen leads to fish death
what does phosphorus limit in lakes
cyanobacterial growth
- more than nitrogen
what affects primary production on a large scale in terrestrial ecosystems
temperature, moisture, soil nutrients
what does NPP increase with in terrestrial ecosystems
precipitation, increasing temperature, and solar energy
most common limiting nutrient in terrestrial ecosystems
nitrogen
- phosphorus as well, but in older soils
adaptations of plants to access limiting nutrients from soil
- mutualisms with nitrogen-fixing bacteria
- mutualisms w/ mycorrhizal fungi
- root hairs to increase surface area
- enzymes that increase availability of limiting nutrients
secondary production
amount of chemical energy in food converted to new biomass during a given period of time
when a caterpillar feeds on a leaf…
only about 1/6 of leaf’s energy used for secondary production
efficiency of birds/mammals
1-3% because of high cost of endothermy
efficiencies of fish
10%
efficiencies of insects and microorganisms
40% or more
trophic efficiency
percentage of production transferred from one trophic level to the next
usual value of trophic efficiency
10%, range of 5-20%
trophic efficiency is ________ over the length of a food chain
multiplied
how much of chemical energy fixed by photosynthesis reaches a tertiary consumer
0.1%
energy pyramid
represents loss of energy w/ each transfer in a food chain
biomass pyramid
each tier represents dry mass of all organisms in one trophic level
- show sharp decrease at higher levels
inverted biomass pyramids of certain aquatic ecosystems
products (phytoplankton) are consumed so quickly that they are outweighed by primary consumers
- zooplankton larger
who plays a key role in the general pattern of chemical cycling
decomposers/cycling
what is the rate of decomposition controlled by
- temperature
- moisture
- nutrient availability
what does rapid decomposition result in
relatively low levels of nutrients in the soil
what do cold and wet ecosystems store
large amounts of undecomposed organic matter, as decomposition rates are low
what slows in anaerobic conditions
decomposition
biogeochemical cycles
nutrient cycles that involve both biotic and abiotic components
what occur in the atmosphere and cycle globally
gaseous carbon, oxygen, sulfur, and nitrogen
less mobile elements
phosphorus, potassium, and calcium
what is essential to all organisms
water and carbon-based organic molecules
where is 97% of biosphere’s water
oceans
2% of biosphere’s water
glaciers and polar ice caps
1% of biosphere’s water
lakes, rivers, groundwater
how does water move (Water Cycle)
- evaporation
- transpiration
- condensation
- precipitation
- movement through surface and groundwater
what do photosynthetic organisms convert CO2 to
organic molecules consumed by heterotrophs
carbon reservoirs inclue (carbon cycle)
- fossil fuels
- soils and sediments
- solutes in oceans
- plant and animal biomass
- atmosphere
- sedimentary rocks
how is CO2 taken up and released
photosynthesis and respiration
what also contributes to CO2 in atmosphere
volcanoes and burning of fossil fuels
what is nitrogen a component of
amino acids, proteins, and nucleic acids
main reservoir of nitrogen
atmosphere (N2)
how do plants uptake nitrogen
N2 from atmosphere must be converted to NH4+ or NO3- via nitrogen fixation by bacteria
- some bacteria can also use NO2-
animals can only use ____________ nitrogen
organic
ammonification
organic nitrogen decomposed to NH4+
nitrification
NH4+ decomposed to NO3-
denitrification
what converts NO3- back to N2
what is phosphorus a major constituent of
nucleic acids, phospholipids, and ATP
most important inorganic form of phosphorus
phosphate (PO43-)
largest reservoir of phosphorus
- sedimentary rocks of marine origin
- soil
- oceans
- organisms
what does the weathering of rocks release
phosphate into the soil, reaches aquatic systems through leaching
