Chapter 21: Movement of Elements in Ecosystems (water, carbon, nitrogen, phosphorous) Flashcards
dead zone
aquatic ecosystems that experience algal blooms + large animal die-offs
- Mississippi river flows into Gulf of Mexico every summer
direct effects of summer algal blooms
some algae or cyanobacteria produce toxins when the bloom
indirect effects of summer algal blooms
phytoplankton bloom and die
- Bacteria consume dead biomass and use lots of O2
- Aquatic life dies from oxygen deprivation
causes of summer algal blooms
nitrogen + phosphorous from fertilizers run-off into streams/rivers, phosphorous from detergents and sewage cause rapid algal growth
- Along with warm temps
required nutrients from biotic and abiotic ecosystems
Hydrogen, oxygen, carbon, nitrogen, and phosphorous
nutrient / biogeochemical cycle
path an element takes as it moves from abiotic systems through living organisms
- via assimilation, consumption, and decomposition
Organisms need 7 major nutrients
nitrogen, phosphorous, sulfur, potassium, calcium, magnesium, and iron
what controls the rate of nutrient cycling?
decomposition of detritus limits the rate at which nutrients move through an ecosystem.
what controls decomposition rate
temperature and moisture
the hydrologic cycle
movement of water through ecosystems and atmosphere
hydrologic cycle components/transfers
evaporation, transpiration, and precipitation
97% of earth’s water is in ___
oceans
Human impacts on the Hydrologic Cycle:
- Roofing/pavement/concrete create surface runoff (can’t hold water like soil)
- Logging (removing trees) decreases precipitation and evapotranspiration
- Draining aquifers quicker than they can be replenished
- Global warming causing temperature rise increasing water evaporation
all organisms are composed of ___
carbon
6 transformations of the carbon cycle
photosynthesis, respiration, sedimentation and burial, extraction, and combustion
nutrient loss from leaching and water transport is balanced by inputs of ___ from the ___ and from ___ of bedrock under the soil
nutrients from the air
the weathering of bedrock
weathering rates can be determined by
measuring nutrients entering a system from rainfall and leaving a system by leaching
- the balance b/w loss and gain of nutrients
watershed
area of land draining into a single stream or river
Photosynthesis and respiration do what?
take CO2 from air and water –> carbohydrates, release some CO2 back
Human impacts on the carbon cycle:
- Extraction and combustion of fossil fuels
previously, CO2 ppm had never surpassed ___, but now its over ___
300 ppm, 405 ppm
Nitrogen is important for:
building proteins and nucleic acids for DNA
Nitrogen fixation
converting atmospheric N2 –> forms producers can use
o N2–> NH3 (ammonia) or NH4+
o Occurs in 3 ways: cyanobacteria/4 types of bacteria, lightening/rain, and production of fertilizer
Nitrification
converts NH4+ or NH3 –> NO2- –> NO3-
- release potential energy by bacteria
- transforms into usable nitrogen
autotrophic river
if primary production exceeds decomposition
heterotrophic river
if decomposition exceeds primary production
- occurs in most streams
Nitrogen Assimilation
producers take up nitrogen and incorporate it into their tissues
- Primary consumers eat producers and assimilate and excrete nitrogen
Nitrogen Mineralization / ammonification
mineralization: breaking down organic compounds into inorganic compounds
ammonification: animals excrete urea, uric acid, or ammonia; decaying plant and animal material is also broken down by ammonifying bacteria into NH3+
Denitrification
process of converting nitrates into nitrogen gas, returns nitrogen into the atmosphere; done by bacteria
o Highly soluble in water
5 major transformations in the nitrogen cycle
nitrogen fixation, nitrification, assimilation, mineralization, and denitrification
plants need ___ nutrients
dissolved
Human impacts on the nitrogen cycle:
Humans have double nitrogen put into terrestrial ecosystems by:
o combustion of fossil fuels
o production of nitrogen fertilizers
o planting nitrogen-fixing crops
