ecosystems Flashcards
photosynthesis
light energy → chemical energy
generates biomass
glucose + carbon dioxide → oxygen + water
energy lost at each trophic level
∼90%
metabolic processes (respiration) & detritus (waste)
gross productivity
energy acquired by a trophic level
net productivity
energy usable by a trophic level
gross productivity - respiration
transfer efficiency
(net productivity of trophic ÷ net productivity of previous trophic level) × 100
ecological niche
role & space an organism fills in an ecosystem
interactions with biotic & abiotic environmental factors
fundamental niche
theoretical potential use of resources
[no competition]
realized niche
actual use of resources
[competition present]
what happens when two species try to occupy the same niche at the same time ?
competitive exclusion or resource partitioning
competitive exclusion principle
two species cannot occupy the same niche at the same time
one species will out-compete the other & the less competitive species will become locally extinct
resource partitioning
two species adapt to occupy different niches rather than one competitively excluding the other
keystone species
species that plays a unique & crucial role in the way an ecosystem functions
(maintain biodiversity, control populations, provide critical resources)
carrying capacity [K]
population size that can be supported indefinitely by the available resources & services of that ecosystem
what determines carrying capacity ?
limiting factors which are biotic or abiotic
e.g. prey or water, respectively
population growth expression
(births + immigration) - (deaths + emigration)
exponential population growth
j-curve
absence of limiting factors
[favorable environmental conditions]
births > deaths
[tend to be r-strategists]
logistic population growth
s-curve
limiting factors present
[density-dependent factors]
births = deaths
carrying capacity reached
density-dependent factors
factors that regulate population growth depending on population density
(e.g. food)
density-independent factors
factors that regulate population growth independent of population density
(e.g drought)
Lincoln Index
(abundance of mobile animals)
(caught₁ × caught₂) ÷ tagged₂
carbon cycle
plants absorb carbon [photosynthesis]
plants release carbon [respiration]
animals assimilate carbon [consumption]
animals release carbon [respiration]
detritivores release carbon [decomposition]
oceans & fossil fuels are carbon reservoirs
nitrogen cycle
nitrogen-fixing bacteria : N₂ → NH₃ [nitrogen fixation]
nitrifying bacteria : NH₃ → NO₃⁻ [nitrification]
plants absorb NO₃⁻ & animals assimilate NO₃⁻
ammonifying bacteria : decomposition → NH₃ [ammonification]
denitrifying bacteria : NO₃⁻ → N₂ [denitrification]
water cycle
evaporation
condensation
precipitation
plants absorb water for photosynthesis
plants release water [transpiration]
plants & animals release water [decompositon]
succession
change in the species structure of an ecological community over time
primary succession
colonization of bare, previously uninhabited areas (e.g. new landmass)
no soil & seedbank
secondary succession
colonization of disturbed, previously inhabited areas (e.g. flooded landmass)
soil & seedbank present
pioneer community
first stage of succession
unstable community dominated by r-strategists
pioneer species
able to photosynthesize & fixate nitrogen
r-strategists (high reproductive & growth rate)
adapted to harsh abiotic conditions
seral community
distinct communities of plant species that dominate during intermediate stages of succession
biodiversity & biomass increase significantly
climax community
final stage of succession
stable community dominated by K-strategists
