Movement of energy and matter in ecosystems Flashcards
first law of thermodynamics
energy can be converted from one form to another but cannot be created or destroyed
second law
Transformations of energy always result in some loss or dissipation of energy
Amount of energy at higher levels
smaller than in producers
also a number of ecological constraints that make the transfer even less efficient
as energy from one trophic level to next is must be transferred via
consumption assimilation and production
What does the energy between trophic levels depends on
efficiency of each step
consumption efficiency
Proportion of the net production of the lower trophic level that is consumed
consumption efficiency =
consumed energy/ net production of the lower trophic level
Not all plant material consumed
assimilation
percent of the consumed energy that becomes available for work or growth
Don’t assimilate all of what you consume- excrete/regurgitate
assimilation efficiency =
assimilated energy/consumed energy
net production efficiency
percentage of assimilated energy that is incorporated into new biomass
Lower in highly active animals
net production efficiency
net production energy/assimilated energy
ecological effiency
percentage of net production from one level compared to the next lower level
ecological efficiency
net production of energy of a trophic level/ net production energy of a lower trophic level
Equivalent to product of 3 steps previously
ecological efficiency explain number of trophic levels
plants avoid being consumed by defences
Less energy moving up trophic levels because of low consumption efficiency
Less transferred supports lower trophic levels
aquatic ecoystems
algae consumed more efficiently leading to support for more trophic levels
standing crop
amount of biomass present at a particular at a particular time in a system
low consumption efficiency by higher trophic level means
biomass residence high
Means energy and standing crop may differ
consumers not eating all the plants
movement of matter through the ecosystem
matter moves between abiotic and biotic
exchange from ocean to atmosphere
relatively fast
exchange from mantle to lithosphere
relatively slow
Rate of exchange between pools
depends on types of biota
flow of matter
no new matter, all recycled
water cycle
water availability affects rates of primary productivity and decomp
human impact on the water cycle
over-abstraction from lakes and rivers vegetation loss soil erosion pollution of surface water and ground aquifers drainage of wetlands climate impacts
What do man made impervious surfaces do
incr runoff and affect groundwater supply- less infiltration of water so decr evapotranspiration
take carbon out of the atmosphere
assimilation by plants and animals
assimilation into soil
organic decomp (animal waste/dead animals and plants)
assimilation by phytoplankton
releasing carbon
fossil fuel
respiration
human impacts on carbon cycle
by burning fossil fuels intoducing carbon back into the cycle that has been out of it for many years eg carbon in form of oil and peat
solutions to high CO2
plant trees
incr phytoplankton
reduce fossil fuel output, renewable energy
nitrogen cycle
most nitrogen is in the atmosphere
How is nitrogen fixed
bacterial fixation, lightning fixation
Burning material releases some material that precipitates into nitrates
Industrial fixation
revolutionised agriculture but incr eutrophication
Increased nitrogen
dominant species get more dominant
decr diversity due to loss of other species
eutrophication
results in incr primary productivity but -ve effects incl species loss, changes in community structure and toxicity
What is the main environmental form of phosphorous
PO4
Phos cycle
v little in the atmosphere
main source of phosphorous
rocks of maritime origin
Human impacts on Phos cycle
livestock waste and P used in inorganic fertilisers both contribute to eutrophication
Over harvesting crops
3 steps of decomp
leaching, partitioning and micropartitioning
key players in decomp
invertebrates and microbes
decomp rates depend on
temp- colder = litter accumulating (because warmer= faster decomp= less accumulation) and more variation in types of soil affects composition of forest
Precip, and groups of organisms
deforestation
incr volume of water runoffs
Incr loss of nutrients
Mining
causes deforestation, physical damage, contamination
Deep disturbance of soil
Heavy machinery compacts soil
Bringing toxic substances to the surface- contamination
fire
important in many ecosystems eg savanas, grasslands:
- germination of seeds
- regeneration of nutrients locked in biomass
- control of pests
Incr temp,water usage, precip and drought due to climate change incr incedence of fire
Habitat fragmentation makes habitats vulnerable to fire
Fire affects nutrient cycling
loss of N and C
Transfer of nutrients to ash
Warmer soil profiles which alter microbial growth and decomp rates
Devastating for ecosystems not adapted to fires
restoration ecology
speed up recovery of degraded ecosystems using knowledge of nutrient cycles
2 strategies: bioremediation and augmentation of ecosystem processes
bioremediation
use organisms to detoxify ecosystems
use plants, bacteria and fungi
These organisms can: absorb and conc toxic compounds facilitating removal from environment
Metabolise toxic molecules into inorganic or non toxic
augmentation
use organisms to add essential materials to a degraded ecosystem
eg nitrogen fixing bacteria to incr available nitrogen in the soil
